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| author | Tom Lane | 2013-12-15 01:23:26 +0000 |
|---|---|---|
| committer | Tom Lane | 2013-12-15 01:23:26 +0000 |
| commit | 1b4f7f93b4693858cb983af3cd557f6097dab67b (patch) | |
| tree | 2caa02d898221a2c2c6036284a8973f873f72e33 /src/backend/parser/analyze.c | |
| parent | c03ad5602f529787968fa3201b35c119bbc6d782 (diff) | |
Allow empty target list in SELECT.
This fixes a problem noted as a followup to bug #8648: if a query has a
semantically-empty target list, e.g. SELECT * FROM zero_column_table,
ruleutils.c will dump it as a syntactically-empty target list, which was
not allowed. There doesn't seem to be any reliable way to fix this by
hacking ruleutils (note in particular that the originally zero-column table
might since have had columns added to it); and even if we had such a fix,
it would do nothing for existing dump files that might contain bad syntax.
The best bet seems to be to relax the syntactic restriction.
Also, add parse-analysis errors for SELECT DISTINCT with no columns (after
*-expansion) and RETURNING with no columns. These cases previously
produced unexpected behavior because the parsed Query looked like it had
no DISTINCT or RETURNING clause, respectively. If anyone ever offers
a plausible use-case for this, we could work a bit harder on making the
situation distinguishable.
Arguably this is a bug fix that should be back-patched, but I'm worried
that there may be client apps or PLs that expect "SELECT ;" to throw a
syntax error. The issue doesn't seem important enough to risk changing
behavior in minor releases.
Diffstat (limited to 'src/backend/parser/analyze.c')
| -rw-r--r-- | src/backend/parser/analyze.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c index a9d1fecff5c..60cce378453 100644 --- a/src/backend/parser/analyze.c +++ b/src/backend/parser/analyze.c @@ -2018,6 +2018,19 @@ transformReturningList(ParseState *pstate, List *returningList) /* transform RETURNING identically to a SELECT targetlist */ rlist = transformTargetList(pstate, returningList, EXPR_KIND_RETURNING); + /* + * Complain if the nonempty tlist expanded to nothing (which is possible + * if it contains only a star-expansion of a zero-column table). If we + * allow this, the parsed Query will look like it didn't have RETURNING, + * with results that would probably surprise the user. + */ + if (rlist == NIL) + ereport(ERROR, + (errcode(ERRCODE_SYNTAX_ERROR), + errmsg("RETURNING must have at least one column"), + parser_errposition(pstate, + exprLocation(linitial(returningList))))); + /* mark column origins */ markTargetListOrigins(pstate, rlist); |