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[PATCH v22 2/8] Row pattern recognition patch (parse/analysis).
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* [PATCH v22 2/8] Row pattern recognition patch (parse/analysis).
@ 2024-09-19 04:48  Tatsuo Ishii <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Tatsuo Ishii @ 2024-09-19 04:48 UTC (permalink / raw)

---
 src/backend/parser/parse_agg.c    |   7 +
 src/backend/parser/parse_clause.c | 296 +++++++++++++++++++++++++++++-
 src/backend/parser/parse_expr.c   |   6 +
 src/backend/parser/parse_func.c   |   3 +
 4 files changed, 311 insertions(+), 1 deletion(-)

diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c
index efa730c167..a80263f90d 100644
--- a/src/backend/parser/parse_agg.c
+++ b/src/backend/parser/parse_agg.c
@@ -580,6 +580,10 @@ check_agglevels_and_constraints(ParseState *pstate, Node *expr)
 			errkind = true;
 			break;
 
+		case EXPR_KIND_RPR_DEFINE:
+			errkind = true;
+			break;
+
 			/*
 			 * There is intentionally no default: case here, so that the
 			 * compiler will warn if we add a new ParseExprKind without
@@ -970,6 +974,9 @@ transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
 		case EXPR_KIND_CYCLE_MARK:
 			errkind = true;
 			break;
+		case EXPR_KIND_RPR_DEFINE:
+			errkind = true;
+			break;
 
 			/*
 			 * There is intentionally no default: case here, so that the
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 8118036495..9762dce81f 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -98,7 +98,14 @@ static WindowClause *findWindowClause(List *wclist, const char *name);
 static Node *transformFrameOffset(ParseState *pstate, int frameOptions,
 								  Oid rangeopfamily, Oid rangeopcintype, Oid *inRangeFunc,
 								  Node *clause);
-
+static void transformRPR(ParseState *pstate, WindowClause *wc, WindowDef *windef,
+						 List **targetlist);
+static List *transformDefineClause(ParseState *pstate, WindowClause *wc, WindowDef *windef,
+								   List **targetlist);
+static void transformPatternClause(ParseState *pstate, WindowClause *wc,
+								   WindowDef *windef);
+static List *transformMeasureClause(ParseState *pstate, WindowClause *wc,
+									WindowDef *windef);
 
 /*
  * transformFromClause -
@@ -2956,6 +2963,10 @@ transformWindowDefinitions(ParseState *pstate,
 											 rangeopfamily, rangeopcintype,
 											 &wc->endInRangeFunc,
 											 windef->endOffset);
+
+		/* Process Row Pattern Recognition related clauses */
+		transformRPR(pstate, wc, windef, targetlist);
+
 		wc->winref = winref;
 
 		result = lappend(result, wc);
@@ -3820,3 +3831,286 @@ transformFrameOffset(ParseState *pstate, int frameOptions,
 
 	return node;
 }
+
+/*
+ * transformRPR
+ *		Process Row Pattern Recognition related clauses
+ */
+static void
+transformRPR(ParseState *pstate, WindowClause *wc, WindowDef *windef,
+			 List **targetlist)
+{
+	/*
+	 * Window definition exists?
+	 */
+	if (windef == NULL)
+		return;
+
+	/*
+	 * Row Pattern Common Syntax clause exists?
+	 */
+	if (windef->rpCommonSyntax == NULL)
+		return;
+
+	/* Check Frame option. Frame must start at current row */
+	if ((wc->frameOptions & FRAMEOPTION_START_CURRENT_ROW) == 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("FRAME must start at current row when row patttern recognition is used")));
+
+	/* Transform AFTER MACH SKIP TO clause */
+	wc->rpSkipTo = windef->rpCommonSyntax->rpSkipTo;
+
+	/* Transform AFTER MACH SKIP TO variable */
+	wc->rpSkipVariable = windef->rpCommonSyntax->rpSkipVariable;
+
+	/* Transform SEEK or INITIAL clause */
+	wc->initial = windef->rpCommonSyntax->initial;
+
+	/* Transform DEFINE clause into list of TargetEntry's */
+	wc->defineClause = transformDefineClause(pstate, wc, windef, targetlist);
+
+	/* Check PATTERN clause and copy to patternClause */
+	transformPatternClause(pstate, wc, windef);
+
+	/* Transform MEASURE clause */
+	transformMeasureClause(pstate, wc, windef);
+}
+
+/*
+ * transformDefineClause Process DEFINE clause and transform ResTarget into
+ *		list of TargetEntry.
+ *
+ * XXX we only support column reference in row pattern definition search
+ * condition, e.g. "price". <row pattern definition variable name>.<column
+ * reference> is not supported, e.g. "A.price".
+ */
+static List *
+transformDefineClause(ParseState *pstate, WindowClause *wc, WindowDef *windef,
+					  List **targetlist)
+{
+	/* DEFINE variable name initials */
+	static char *defineVariableInitials = "abcdefghijklmnopqrstuvwxyz";
+
+	ListCell   *lc,
+			   *l;
+	ResTarget  *restarget,
+			   *r;
+	List	   *restargets;
+	List	   *defineClause;
+	char	   *name;
+	int			initialLen;
+	int			i;
+
+	/*
+	 * If Row Definition Common Syntax exists, DEFINE clause must exist. (the
+	 * raw parser should have already checked it.)
+	 */
+	Assert(windef->rpCommonSyntax->rpDefs != NULL);
+
+	/*
+	 * Check and add "A AS A IS TRUE" if pattern variable is missing in DEFINE
+	 * per the SQL standard.
+	 */
+	restargets = NIL;
+	foreach(lc, windef->rpCommonSyntax->rpPatterns)
+	{
+		A_Expr	   *a;
+		bool		found = false;
+
+		if (!IsA(lfirst(lc), A_Expr))
+			ereport(ERROR,
+					errmsg("node type is not A_Expr"));
+
+		a = (A_Expr *) lfirst(lc);
+		name = strVal(a->lexpr);
+
+		foreach(l, windef->rpCommonSyntax->rpDefs)
+		{
+			restarget = (ResTarget *) lfirst(l);
+
+			if (!strcmp(restarget->name, name))
+			{
+				found = true;
+				break;
+			}
+		}
+
+		if (!found)
+		{
+			/*
+			 * "name" is missing. So create "name AS name IS TRUE" ResTarget
+			 * node and add it to the temporary list.
+			 */
+			A_Const    *n;
+
+			restarget = makeNode(ResTarget);
+			n = makeNode(A_Const);
+			n->val.boolval.type = T_Boolean;
+			n->val.boolval.boolval = true;
+			n->location = -1;
+			restarget->name = pstrdup(name);
+			restarget->indirection = NIL;
+			restarget->val = (Node *) n;
+			restarget->location = -1;
+			restargets = lappend((List *) restargets, restarget);
+		}
+	}
+
+	if (list_length(restargets) >= 1)
+	{
+		/* add missing DEFINEs */
+		windef->rpCommonSyntax->rpDefs =
+			list_concat(windef->rpCommonSyntax->rpDefs, restargets);
+		list_free(restargets);
+	}
+
+	/*
+	 * Check for duplicate row pattern definition variables.  The standard
+	 * requires that no two row pattern definition variable names shall be
+	 * equivalent.
+	 */
+	restargets = NIL;
+	foreach(lc, windef->rpCommonSyntax->rpDefs)
+	{
+		restarget = (ResTarget *) lfirst(lc);
+		name = restarget->name;
+
+		/*
+		 * Add DEFINE expression (Restarget->val) to the targetlist as a
+		 * TargetEntry if it does not exist yet. Planner will add the column
+		 * ref var node to the outer plan's target list later on. This makes
+		 * DEFINE expression could access the outer tuple while evaluating
+		 * PATTERN.
+		 *
+		 * XXX: adding whole expressions of DEFINE to the plan.targetlist is
+		 * not so good, because it's not necessary to evalute the expression
+		 * in the target list while running the plan. We should extract the
+		 * var nodes only then add them to the plan.targetlist.
+		 */
+		findTargetlistEntrySQL99(pstate, (Node *) restarget->val,
+								 targetlist, EXPR_KIND_RPR_DEFINE);
+
+		/*
+		 * Make sure that the row pattern definition search condition is a
+		 * boolean expression.
+		 */
+		transformWhereClause(pstate, restarget->val,
+							 EXPR_KIND_RPR_DEFINE, "DEFINE");
+
+		foreach(l, restargets)
+		{
+			char	   *n;
+
+			r = (ResTarget *) lfirst(l);
+			n = r->name;
+
+			if (!strcmp(n, name))
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("row pattern definition variable name \"%s\" appears more than once in DEFINE clause",
+								name),
+						 parser_errposition(pstate, exprLocation((Node *) r))));
+		}
+		restargets = lappend(restargets, restarget);
+	}
+	list_free(restargets);
+
+	/*
+	 * Create list of row pattern DEFINE variable name's initial. We assign
+	 * [a-z] to them (up to 26 variable names are allowed).
+	 */
+	restargets = NIL;
+	i = 0;
+	initialLen = strlen(defineVariableInitials);
+
+	foreach(lc, windef->rpCommonSyntax->rpDefs)
+	{
+		char		initial[2];
+
+		restarget = (ResTarget *) lfirst(lc);
+		name = restarget->name;
+
+		if (i >= initialLen)
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+					 errmsg("number of row pattern definition variable names exceeds %d",
+							initialLen),
+					 parser_errposition(pstate,
+										exprLocation((Node *) restarget))));
+		}
+		initial[0] = defineVariableInitials[i++];
+		initial[1] = '\0';
+		wc->defineInitial = lappend(wc->defineInitial,
+									makeString(pstrdup(initial)));
+	}
+
+	defineClause = transformTargetList(pstate, windef->rpCommonSyntax->rpDefs,
+									   EXPR_KIND_RPR_DEFINE);
+
+	/* mark column origins */
+	markTargetListOrigins(pstate, defineClause);
+
+	/* mark all nodes in the DEFINE clause tree with collation information */
+	assign_expr_collations(pstate, (Node *) defineClause);
+
+	return defineClause;
+}
+
+/*
+ * transformPatternClause
+ *		Process PATTERN clause and return PATTERN clause in the raw parse tree
+ */
+static void
+transformPatternClause(ParseState *pstate, WindowClause *wc,
+					   WindowDef *windef)
+{
+	ListCell   *lc;
+
+	/*
+	 * Row Pattern Common Syntax clause exists?
+	 */
+	if (windef->rpCommonSyntax == NULL)
+		return;
+
+	wc->patternVariable = NIL;
+	wc->patternRegexp = NIL;
+	foreach(lc, windef->rpCommonSyntax->rpPatterns)
+	{
+		A_Expr	   *a;
+		char	   *name;
+		char	   *regexp;
+
+		if (!IsA(lfirst(lc), A_Expr))
+			ereport(ERROR,
+					errmsg("node type is not A_Expr"));
+
+		a = (A_Expr *) lfirst(lc);
+		name = strVal(a->lexpr);
+
+		wc->patternVariable = lappend(wc->patternVariable, makeString(pstrdup(name)));
+		regexp = strVal(lfirst(list_head(a->name)));
+
+		wc->patternRegexp = lappend(wc->patternRegexp, makeString(pstrdup(regexp)));
+	}
+}
+
+/*
+ * transformMeasureClause
+ *		Process MEASURE clause
+ *	XXX MEASURE clause is not supported yet
+ */
+static List *
+transformMeasureClause(ParseState *pstate, WindowClause *wc,
+					   WindowDef *windef)
+{
+	if (windef->rowPatternMeasures == NIL)
+		return NIL;
+
+	ereport(ERROR,
+			(errcode(ERRCODE_SYNTAX_ERROR),
+			 errmsg("%s", "MEASURE clause is not supported yet"),
+			 parser_errposition(pstate, exprLocation((Node *) windef->rowPatternMeasures))));
+	return NIL;
+}
diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index 36c1b7a88f..fe154bcaa0 100644
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -577,6 +577,7 @@ transformColumnRef(ParseState *pstate, ColumnRef *cref)
 		case EXPR_KIND_COPY_WHERE:
 		case EXPR_KIND_GENERATED_COLUMN:
 		case EXPR_KIND_CYCLE_MARK:
+		case EXPR_KIND_RPR_DEFINE:
 			/* okay */
 			break;
 
@@ -1860,6 +1861,9 @@ transformSubLink(ParseState *pstate, SubLink *sublink)
 		case EXPR_KIND_GENERATED_COLUMN:
 			err = _("cannot use subquery in column generation expression");
 			break;
+		case EXPR_KIND_RPR_DEFINE:
+			err = _("cannot use subquery in DEFINE expression");
+			break;
 
 			/*
 			 * There is intentionally no default: case here, so that the
@@ -3199,6 +3203,8 @@ ParseExprKindName(ParseExprKind exprKind)
 			return "GENERATED AS";
 		case EXPR_KIND_CYCLE_MARK:
 			return "CYCLE";
+		case EXPR_KIND_RPR_DEFINE:
+			return "DEFINE";
 
 			/*
 			 * There is intentionally no default: case here, so that the
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 9b23344a3b..4c482abb30 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -2658,6 +2658,9 @@ check_srf_call_placement(ParseState *pstate, Node *last_srf, int location)
 		case EXPR_KIND_CYCLE_MARK:
 			errkind = true;
 			break;
+		case EXPR_KIND_RPR_DEFINE:
+			errkind = true;
+			break;
 
 			/*
 			 * There is intentionally no default: case here, so that the
-- 
2.25.1


----Next_Part(Thu_Sep_19_13_59_47_2024_608)--
Content-Type: Text/X-Patch; charset=us-ascii
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
 filename="v22-0003-Row-pattern-recognition-patch-rewriter.patch"



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
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^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
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Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
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^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
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Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
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Content-Transfer-Encoding: 7bit
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^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
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Content-Transfer-Encoding: 7bit
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^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


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^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


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^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
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Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
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Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
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Content-Transfer-Encoding: 7bit
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^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
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Content-Transfer-Encoding: 7bit
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^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
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Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
Content-Type: text/x-patch
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
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^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


--MP_/4ZRYdF7Ah.pt5w65PuZdaPz
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Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename=v3-0002-Error-out-if-one-iteration-of-non-direct-DML-affe.patch



^ permalink  raw  reply  [nested|flat] 817+ messages in thread

* [PATCH v3 1/2] Test exposing bug when foreign table points to a partitioned table
@ 2025-07-15 10:45  Jehan-Guillaume de Rorthais <[email protected]>
  0 siblings, 0 replies; 817+ messages in thread

From: Jehan-Guillaume de Rorthais @ 2025-07-15 10:45 UTC (permalink / raw)

When a foreign table points to a partitioned table or an inheritance
parent on the foreign server, a non-direct DML can affect multiple
rows when only one row is intended to be affected. This
happens because postgres_fdw uses only ctid to identify a row to work
on. Though ctid uniquely identifies a row in a single table, in a
partitioned table or in an inheritance hierarchy, there can be be
multiple rows, in different partitions, with the same ctid. So
DML statement sent to the foreign server by postgres_fdw ends up
affecting more than one rows, only one of which is intended to be
affected.

This commit adds testcases to show the problem. A subsequent commit
would have a fix to the problem.

Author: Ashutosh Bapat <[email protected]>
Reviewed-by: Kyotaro Horiguchi <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CAFjFpRfcgwsHRmpvoOK-GUQi-n8MgAS%2BOxcQo%3DaBDn1COywmcg%4...

Rebased by Jehan-Guillaume de Rorthais <[email protected]>
---
 .../postgres_fdw/expected/postgres_fdw.out    | 125 ++++++++++++++++++
 contrib/postgres_fdw/sql/postgres_fdw.sql     |  58 ++++++++
 2 files changed, 183 insertions(+)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 2185b42bb4f..62019eaa881 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8954,6 +8954,131 @@ drop foreign table remt2;
 drop table loct1;
 drop table loct2;
 drop table parent;
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa  
+----------+-------+-----
+ fa       | (0,1) | aaa
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Update on public.fa
+   Remote SQL: UPDATE public.a SET aa = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 'zzzz'::text ELSE NULL::text END, ctid, fa.*
+         Remote SQL: SELECT aa, ctid FROM public.a WHERE ((aa = 'aaa')) FOR UPDATE
+(5 rows)
+
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  |  aa  
+----------+-------+------
+ fa       | (0,2) | zzzz
+ fa       | (0,1) | bbb
+(2 rows)
+
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+                                                  QUERY PLAN                                                   
+---------------------------------------------------------------------------------------------------------------
+ Delete on public.fa
+   Remote SQL: DELETE FROM public.a WHERE ctid = $1
+   ->  Foreign Scan on public.fa
+         Output: ctid
+         Filter: (fa.aa = CASE WHEN (random() <= '1'::double precision) THEN 'aaa'::text ELSE 'bbb'::text END)
+         Remote SQL: SELECT aa, ctid FROM public.a FOR UPDATE
+(6 rows)
+
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+ tableoid | ctid  | aa 
+----------+-------+-----
+ fa       | (0,1) | bbb
+(1 row)
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+NOTICE:  drop cascades to table b
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 1 | 1
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Update on public.fplt
+   Remote SQL: UPDATE public.plt SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: CASE WHEN (random() <= '1'::double precision) THEN 10 ELSE 20 END, ctid, fplt.*
+         Remote SQL: SELECT a, b, ctid FROM public.plt WHERE ((a = 1)) FOR UPDATE
+(5 rows)
+
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b  
+----------+-------+---+----
+ fplt     | (0,2) | 1 | 10
+ fplt     | (0,1) | 2 | 2
+(2 rows)
+
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.fplt
+   Remote SQL: DELETE FROM public.plt WHERE ctid = $1
+   ->  Foreign Scan on public.fplt
+         Output: ctid
+         Filter: (fplt.a = CASE WHEN (random() <= '1'::double precision) THEN 1 ELSE 10 END)
+         Remote SQL: SELECT a, ctid FROM public.plt FOR UPDATE
+(6 rows)
+
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+ tableoid | ctid  | a | b 
+----------+-------+---+---
+ fplt     | (0,1) | 2 | 2 
+(1 row)
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index e534b40de3c..ae3777b7edb 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2494,6 +2494,64 @@ drop table loct1;
 drop table loct2;
 drop table parent;
 
+-- test DML statement on a foreign table pointing to an inheritance hierarchy
+-- on the remote server
+CREATE TABLE a(aa TEXT);
+ALTER TABLE a SET (autovacuum_enabled = 'false');
+CREATE TABLE b() INHERITS(a);
+ALTER TABLE b SET (autovacuum_enabled = 'false');
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+CREATE FOREIGN TABLE fa (aa TEXT) SERVER loopback OPTIONS (table_name 'a');
+
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+UPDATE fa SET aa = (CASE WHEN random() <= 1 THEN 'zzzz' ELSE NULL END) WHERE aa = 'aaa';
+SELECT tableoid::regclass, ctid, * FROM fa;
+-- repopulate tables so that we have rows with same ctid
+TRUNCATE a, b;
+INSERT INTO a(aa) VALUES('aaa');
+INSERT INTO b(aa) VALUES('bbb');
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+DELETE FROM fa WHERE aa = (CASE WHEN random() <= 1 THEN 'aaa' ELSE 'bbb' END);
+SELECT tableoid::regclass, ctid, * FROM fa;
+
+-- cleanup
+DROP FOREIGN TABLE fa;
+DROP TABLE a CASCADE;
+
+-- ===================================================================
+-- test foreign table pointing to a remote partitioned table
+-- ===================================================================
+
+-- test DML statement on foreign table pointing to a foreign partitioned table
+CREATE TABLE plt (a int, b int) PARTITION BY LIST(a);
+CREATE TABLE plt_p1 PARTITION OF plt FOR VALUES IN (1);
+CREATE TABLE plt_p2 PARTITION OF plt FOR VALUES IN (2);
+INSERT INTO plt VALUES (1, 1), (2, 2);
+CREATE FOREIGN TABLE fplt (a int, b int) SERVER loopback OPTIONS (table_name 'plt');
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- use random() so that DML statement is not pushed down to the foreign
+-- server
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+UPDATE fplt SET b = (CASE WHEN random() <= 1 THEN 10 ELSE 20 END) WHERE a = 1;
+SELECT tableoid::regclass, ctid, * FROM fplt;
+-- repopulate partitioned table so that we have rows with same ctid
+TRUNCATE plt;
+INSERT INTO plt VALUES (1, 1), (2, 2);
+EXPLAIN (VERBOSE, COSTS OFF)
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+DELETE FROM fplt WHERE a = (CASE WHEN random() <=  1 THEN 1 ELSE 10 END);
+SELECT tableoid::regclass, ctid, * FROM fplt;
+
+DROP TABLE plt;
+DROP FOREIGN TABLE fplt;
+
 -- ===================================================================
 -- test tuple routing for foreign-table partitions
 -- ===================================================================
-- 
2.50.0


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