From ec1536f806a4689ee287aa4b7102618c55e399ed Mon Sep 17 00:00:00 2001 From: Alvaro Herrera Date: Thu, 11 Aug 2022 13:17:58 +0200 Subject: [PATCH v2] Reject MERGE in CTEs and COPY 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 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(+) diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c index 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.c index 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.out index 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.sql index 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