From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Subject: [PATCH v2] Reject MERGE in CTEs and COPY
Date: Thu, 11 Aug 2022 13:17:58 +0200
The grammar added for MERGE inadvertently made it accepted syntax in
places that were not prepared to deal with it -- namely COPY and inside
CTEs, but invoking these things with MERGE currently causes assertion
failures or weird misbehavior in non-assertion builds. Protect those
places by checking for it explicitly until somebody decides to implement
it.
Reported-by: Alexey Borzov <borz_off@cs.msu.su>
Discussion: https://postgr.es/m/17579-82482cd7b267b862@postgresql.org
---
src/backend/commands/copy.c | 6 ++++++
src/backend/parser/parse_cte.c | 7 +++++++
src/test/regress/expected/merge.out | 14 ++++++++++++++
src/test/regress/sql/merge.sql | 10 ++++++++++
4 files changed, 37 insertions(+)
inline patch 1: src/backend/commands/copy.c, src/backend/parser/parse_cte.c, src/test/regress/expected/merge.out and 1 more (+37/-0 lines) download inline-1.patchdiff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.cindex 3ac731803b..49924e476a 100644--- a/src/backend/commands/copy.c+++ b/src/backend/commands/copy.c@@ -273,6 +273,12 @@ DoCopy(ParseState *pstate, const CopyStmt *stmt,
{
Assert(stmt->query);
+ /* MERGE is allowed by parser, but unimplemented. Reject for now */+ if (IsA(stmt->query, MergeStmt))+ ereport(ERROR,+ errcode(ERRCODE_FEATURE_NOT_SUPPORTED),+ errmsg("MERGE not supported in COPY"));+
query = makeNode(RawStmt);
query->stmt = stmt->query;
query->stmt_location = stmt_location;
diff --git a/src/backend/parser/parse_cte.c b/src/backend/parser/parse_cte.cindex efb4af706e..8fc8658608 100644--- a/src/backend/parser/parse_cte.c+++ b/src/backend/parser/parse_cte.c@@ -126,6 +126,13 @@ transformWithClause(ParseState *pstate, WithClause *withClause)
CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc);
ListCell *rest;
+ /* MERGE is allowed by parser, but unimplemented. Reject for now */+ if (IsA(cte->ctequery, MergeStmt))+ ereport(ERROR,+ errcode(ERRCODE_FEATURE_NOT_SUPPORTED),+ errmsg("MERGE not supported in WITH query"),+ parser_errposition(pstate, cte->location));+
for_each_cell(rest, withClause->ctes, lnext(withClause->ctes, lc))
{
CommonTableExpr *cte2 = (CommonTableExpr *) lfirst(rest);
diff --git a/src/test/regress/expected/merge.out b/src/test/regress/expected/merge.outindex af670e28e7..729ae2eb06 100644--- a/src/test/regress/expected/merge.out+++ b/src/test/regress/expected/merge.out@@ -123,6 +123,20 @@ ON tid = tid
WHEN MATCHED THEN DO NOTHING;
ERROR: name "target" specified more than once
DETAIL: The name is used both as MERGE target table and data source.
+-- used in a CTE+WITH foo AS (+ MERGE INTO target USING source ON (true)+ WHEN MATCHED THEN DELETE+) SELECT * FROM foo;+ERROR: MERGE not supported in WITH query+LINE 1: WITH foo AS (+ ^+-- used in COPY+COPY (+ MERGE INTO target USING source ON (true)+ WHEN MATCHED THEN DELETE+) TO stdout;+ERROR: MERGE not supported in COPY
-- unsupported relation types
-- view
CREATE VIEW tv AS SELECT * FROM target;
diff --git a/src/test/regress/sql/merge.sql b/src/test/regress/sql/merge.sqlindex afeb212f3c..e0c450736b 100644--- a/src/test/regress/sql/merge.sql+++ b/src/test/regress/sql/merge.sql@@ -88,6 +88,16 @@ MERGE INTO target
USING target
ON tid = tid
WHEN MATCHED THEN DO NOTHING;
+-- used in a CTE+WITH foo AS (+ MERGE INTO target USING source ON (true)+ WHEN MATCHED THEN DELETE+) SELECT * FROM foo;+-- used in COPY+COPY (+ MERGE INTO target USING source ON (true)+ WHEN MATCHED THEN DELETE+) TO stdout;
-- unsupported relation types
-- view
--
2.30.2
--p5zrfmarbv2alhew--
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To: pgsql-bugs@postgresql.org
Cc: alvherre@alvh.no-ip.org
Subject: Re: [PATCH v2] Reject MERGE in CTEs and COPY
In-Reply-To: <no-message-id-29318@localhost>
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