Subject: [PATCH v9 2/4] WIP: Check for volatile defaults

From: Justin Pryzby <[email-masked]>
Date: Tue, 1 Dec 2020 23:11:31 -0600

We want to check if any column *uses* a volatile default value, but after
parsing and rewriting, that information appears to be lost about which column
values are defaults and which were specified.  insertedcols doesn't appear to
be useful for this.  So add a field to track if a TargetEntry is planned with
column default.
---
 src/backend/executor/nodeModifyTable.c | 64 ++++++++++++++++++++++++--
 src/backend/nodes/copyfuncs.c          |  1 +
 src/backend/nodes/equalfuncs.c         |  1 +
 src/backend/nodes/makefuncs.c          |  1 +
 src/backend/nodes/outfuncs.c           |  1 +
 src/backend/nodes/readfuncs.c          |  1 +
 src/backend/optimizer/util/tlist.c     |  1 +
 src/backend/rewrite/rewriteHandler.c   |  3 ++
 src/include/nodes/primnodes.h          |  2 +
 9 files changed, 71 insertions(+), 4 deletions(-)

diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index a53cbeeb2c..2059428e2a 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -50,6 +50,7 @@
 #include "foreign/fdwapi.h"
 #include "miscadmin.h"
 #include "nodes/nodeFuncs.h"
+#include "optimizer/optimizer.h"
 #include "rewrite/rewriteHandler.h"
 #include "storage/bufmgr.h"
 #include "storage/lmgr.h"
@@ -2258,6 +2259,61 @@ ExecModifyTable(PlanState *pstate)
 	return NULL;
 }
 
+/*
+ * Determine if a table has volatile column defaults which are used by a given
+ * planned statement (if the column is not specified or specified as DEFAULT).
+ * This works only for INSERT.
+ */
+static bool
+has_volatile_defaults(ResultRelInfo *resultRelInfo, ModifyTable *node)
+{
+	TupleDesc	tupDesc = RelationGetDescr(resultRelInfo->ri_RelationDesc);
+	Plan		*plan;
+
+	Assert(list_length(node->plans) == 1);
+	plan = linitial(node->plans);
+
+	for (int attnum = 1; attnum <= tupDesc->natts; attnum++)
+	{
+		Form_pg_attribute att = TupleDescAttr(tupDesc, attnum - 1);
+		Expr		*defexpr;
+		TargetEntry	*tle;
+
+		/* We don't need to check dropped/generated attributes */
+		if (att->attisdropped || att->attgenerated)
+			continue;
+
+		tle = list_nth(plan->targetlist, attnum - 1);
+		Assert(tle != NULL);
+		Assert(tle->resno == attnum);
+
+		/*
+		 * If the column was specified with a non-default value, then don't
+		 * check the volatility of its default
+		 */
+		if (!tle->isdefault)
+			continue;
+
+		/* Check the column's default value if one exists */
+		defexpr = (Expr *) build_column_default(resultRelInfo->ri_RelationDesc, attnum);
+		if (defexpr == NULL)
+			continue;
+
+		/* Run the expression through planner */
+		// defexpr = expression_planner(defexpr);
+		// (void) ExecInitExpr(defexpr, NULL);
+		expression_planner(defexpr);
+
+		if (contain_volatile_functions_not_nextval((Node *) defexpr))
+		{
+			elog(DEBUG1, "found volatile att %d", attnum);
+			return true;
+		}
+	}
+
+	return false;
+}
+
 /* ----------------------------------------------------------------
  *		ExecInitModifyTable
  * ----------------------------------------------------------------
@@ -2352,10 +2408,10 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 		 * are any statement level insert triggers.
 		 */
 		mtstate->miinfo = NULL;
-	else if (mtstate->rootResultRelInfo->ri_FdwRoutine != NULL
-			/* || cstate->volatile_defexprs */ )
-		// XXX contain_volatile_functions_not_nextval((Node *) defexpr);
-		/* Can't support multi-inserts to foreign tables or if there are any */
+	else if (mtstate->rootResultRelInfo->ri_FdwRoutine != NULL ||
+			has_volatile_defaults(mtstate->rootResultRelInfo, node))
+		/* Can't support multi-inserts to foreign tables or if there are any
+		 * volatile default expressions in the table. */
 		mtstate->miinfo = NULL;
 	else
 	{
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index ba3ccc712c..2008e8e5d6 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2178,6 +2178,7 @@ _copyTargetEntry(const TargetEntry *from)
 	COPY_SCALAR_FIELD(resorigtbl);
 	COPY_SCALAR_FIELD(resorigcol);
 	COPY_SCALAR_FIELD(resjunk);
+	COPY_SCALAR_FIELD(isdefault);
 
 	return newnode;
 }
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index a2ef853dc2..aa3cdf3729 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -770,6 +770,7 @@ _equalTargetEntry(const TargetEntry *a, const TargetEntry *b)
 	COMPARE_SCALAR_FIELD(resorigtbl);
 	COMPARE_SCALAR_FIELD(resorigcol);
 	COMPARE_SCALAR_FIELD(resjunk);
+	COMPARE_SCALAR_FIELD(isdefault);
 
 	return true;
 }
diff --git a/src/backend/nodes/makefuncs.c b/src/backend/nodes/makefuncs.c
index 01c110cd2f..aeeba7032f 100644
--- a/src/backend/nodes/makefuncs.c
+++ b/src/backend/nodes/makefuncs.c
@@ -254,6 +254,7 @@ makeTargetEntry(Expr *expr,
 	tle->ressortgroupref = 0;
 	tle->resorigtbl = InvalidOid;
 	tle->resorigcol = 0;
+	tle->isdefault = false;
 
 	tle->resjunk = resjunk;
 
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 8392be6d44..924ffda1c6 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -1661,6 +1661,7 @@ _outTargetEntry(StringInfo str, const TargetEntry *node)
 	WRITE_OID_FIELD(resorigtbl);
 	WRITE_INT_FIELD(resorigcol);
 	WRITE_BOOL_FIELD(resjunk);
+	WRITE_BOOL_FIELD(isdefault);
 }
 
 static void
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index d2c8d58070..642b6c63c5 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -1275,6 +1275,7 @@ _readTargetEntry(void)
 	READ_OID_FIELD(resorigtbl);
 	READ_INT_FIELD(resorigcol);
 	READ_BOOL_FIELD(resjunk);
+	READ_BOOL_FIELD(isdefault);
 
 	READ_DONE();
 }
diff --git a/src/backend/optimizer/util/tlist.c b/src/backend/optimizer/util/tlist.c
index 89853a0630..7ef1517027 100644
--- a/src/backend/optimizer/util/tlist.c
+++ b/src/backend/optimizer/util/tlist.c
@@ -349,6 +349,7 @@ apply_tlist_labeling(List *dest_tlist, List *src_tlist)
 		dest_tle->resorigtbl = src_tle->resorigtbl;
 		dest_tle->resorigcol = src_tle->resorigcol;
 		dest_tle->resjunk = src_tle->resjunk;
+		dest_tle->isdefault = src_tle->isdefault;
 	}
 }
 
diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index 0c7508a0d8..7ab13e51e5 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -986,10 +986,13 @@ rewriteTargetListIU(List *targetList,
 			}
 
 			if (new_expr)
+			{
 				new_tle = makeTargetEntry((Expr *) new_expr,
 										  attrno,
 										  pstrdup(NameStr(att_tup->attname)),
 										  false);
+				new_tle->isdefault = true;
+			}
 		}
 
 		/*
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index d4ce037088..888bd36a07 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -1437,6 +1437,8 @@ typedef struct TargetEntry
 	AttrNumber	resorigcol;		/* column's number in source table */
 	bool		resjunk;		/* set to true to eliminate the attribute from
 								 * final target list */
+	bool		isdefault;		/* true if using the column default, either
+								 * by "DEFAULT" or omission of the column */
 } TargetEntry;

-- 
2.17.0

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