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Re-allow DISTINCT in pl/pgsql expressions.

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I'd omitted this from the grammar in commit c9d529848, figuring that
it wasn't worth supporting.  However we already have one complaint,
so it seems that judgment was wrong.  It doesn't require a huge
amount of code, so add it back.  (I'm still drawing the line at
UNION/INTERSECT/EXCEPT though: those'd require an unreasonable
amount of grammar refactoring, and the single-result-row restriction
makes them near useless anyway.)

Also rethink the documentation: this behavior is a property of
all pl/pgsql expressions, not just assignments.

Discussion: https://postgr.es/m/20210122134106.e94c5cd7@mail.verfriemelt.org
This commit is contained in:
Tom Lane
2021-01-22 16:26:22 -05:00
parent ab66645628
commit 7cd9765f9b
3 changed files with 70 additions and 35 deletions
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29
src/backend/parser/analyze.c
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@@ -2466,7 +2466,7 @@ transformPLAssignStmt(ParseState *pstate, PLAssignStmt *stmt)
/*
* The rest mostly matches transformSelectStmt, except that we needn't
* consider WITH or DISTINCT, and we build a targetlist our own way.
* consider WITH or INTO, and we build a targetlist our own way.
*/
qry->commandType = CMD_SELECT;
pstate->p_is_insert = false;
@@ -2590,10 +2590,29 @@ transformPLAssignStmt(ParseState *pstate, PLAssignStmt *stmt)
EXPR_KIND_GROUP_BY,
false /* allow SQL92 rules */ );
/* No DISTINCT clause */
Assert(!sstmt->distinctClause);
qry->distinctClause = NIL;
qry->hasDistinctOn = false;
if (sstmt->distinctClause == NIL)
{
qry->distinctClause = NIL;
qry->hasDistinctOn = false;
}
else if (linitial(sstmt->distinctClause) == NULL)
{
/* We had SELECT DISTINCT */
qry->distinctClause = transformDistinctClause(pstate,
&qry->targetList,
qry->sortClause,
false);
qry->hasDistinctOn = false;
}
else
{
/* We had SELECT DISTINCT ON */
qry->distinctClause = transformDistinctOnClause(pstate,
sstmt->distinctClause,
&qry->targetList,
qry->sortClause);
qry->hasDistinctOn = true;
}
/* transform LIMIT */
qry->limitOffset = transformLimitClause(pstate, sstmt->limitOffset,