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Commit455d254

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Reject MERGE in CTEs and COPY
The grammar added for MERGE inadvertently made it accepted syntax inplaces that were not prepared to deal with it -- namely COPY and insideCTEs, but invoking these things with MERGE currently causes assertionfailures or weird misbehavior in non-assertion builds. Protect thoseplaces by checking for it explicitly until somebody decides to implementit.Reported-by: Alexey Borzov <borz_off@cs.msu.su>Discussion:https://postgr.es/m/17579-82482cd7b267b862@postgresql.org
1 parente1878cf commit455d254

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4 files changed

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‎src/backend/commands/copy.c

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@@ -273,6 +273,12 @@ DoCopy(ParseState *pstate, const CopyStmt *stmt,
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{
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Assert(stmt->query);
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/* MERGE is allowed by parser, but unimplemented. Reject for now */
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if (IsA(stmt->query,MergeStmt))
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ereport(ERROR,
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errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
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errmsg("MERGE not supported in COPY"));
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query=makeNode(RawStmt);
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query->stmt=stmt->query;
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query->stmt_location=stmt_location;

‎src/backend/parser/parse_cte.c

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Original file line numberDiff line numberDiff line change
@@ -126,6 +126,13 @@ transformWithClause(ParseState *pstate, WithClause *withClause)
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CommonTableExpr*cte= (CommonTableExpr*)lfirst(lc);
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ListCell*rest;
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/* MERGE is allowed by parser, but unimplemented. Reject for now */
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if (IsA(cte->ctequery,MergeStmt))
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ereport(ERROR,
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errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
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errmsg("MERGE not supported in WITH query"),
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parser_errposition(pstate,cte->location));
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for_each_cell(rest,withClause->ctes,lnext(withClause->ctes,lc))
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{
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CommonTableExpr*cte2= (CommonTableExpr*)lfirst(rest);

‎src/test/regress/expected/merge.out

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Original file line numberDiff line numberDiff line change
@@ -123,6 +123,20 @@ ON tid = tid
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WHEN MATCHED THEN DO NOTHING;
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ERROR: name "target" specified more than once
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DETAIL: The name is used both as MERGE target table and data source.
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-- used in a CTE
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WITH foo AS (
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MERGE INTO target USING source ON (true)
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WHEN MATCHED THEN DELETE
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) SELECT * FROM foo;
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ERROR: MERGE not supported in WITH query
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LINE 1: WITH foo AS (
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^
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-- used in COPY
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COPY (
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MERGE INTO target USING source ON (true)
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WHEN MATCHED THEN DELETE
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) TO stdout;
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ERROR: MERGE not supported in COPY
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-- unsupported relation types
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-- view
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CREATE VIEW tv AS SELECT * FROM target;

‎src/test/regress/sql/merge.sql

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Original file line numberDiff line numberDiff line change
@@ -88,6 +88,16 @@ MERGE INTO target
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USING target
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ON tid= tid
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WHEN MATCHED THEN DO NOTHING;
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-- used in a CTE
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WITH fooAS (
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MERGE INTO target USING sourceON (true)
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WHEN MATCHED THENDELETE
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)SELECT*FROM foo;
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-- used in COPY
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COPY (
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MERGE INTO target USING sourceON (true)
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WHEN MATCHED THENDELETE
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) TO stdout;
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-- unsupported relation types
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-- view

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