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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2016-07-26 15:25:02 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2016-07-26 15:25:02 -0400 |
| commit | 0733188ccfcef37d715a9b29d5dc987a369a0c86 (patch) | |
| tree | 59629a0a1ee67a46d1d984529d03083a2b4cf84e /src/backend/optimizer/util/clauses.c | |
| parent | f0c9e4697757d27b9e8ccd76d8b330af09f58bf7 (diff) | |
Fix constant-folding of ROW(...) IS [NOT] NULL with composite fields.
The SQL standard appears to specify that IS [NOT] NULL's tests of field
nullness are non-recursive, ie, we shouldn't consider that a composite
field with value ROW(NULL,NULL) is null for this purpose.
ExecEvalNullTest got this right, but eval_const_expressions did not,
leading to weird inconsistencies depending on whether the expression
was such that the planner could apply constant folding.
Also, adjust the docs to mention that IS [NOT] DISTINCT FROM NULL can be
used as a substitute test if a simple null check is wanted for a rowtype
argument. That motivated reordering things so that IS [NOT] DISTINCT FROM
is described before IS [NOT] NULL. In HEAD, I went a bit further and added
a table showing all the comparison-related predicates.
Per bug #14235. Back-patch to all supported branches, since it's certainly
undesirable that constant-folding should change the semantics.
Report and patch by Andrew Gierth; assorted wordsmithing and revised
regression test cases by me.
Report: <20160708024746.1410.57282@wrigleys.postgresql.org>
Diffstat (limited to 'src/backend/optimizer/util/clauses.c')
| -rw-r--r-- | src/backend/optimizer/util/clauses.c | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c index 47e29cfc492..a35e3565e18 100644 --- a/src/backend/optimizer/util/clauses.c +++ b/src/backend/optimizer/util/clauses.c @@ -3269,7 +3269,7 @@ eval_const_expressions_mutator(Node *node, arg = eval_const_expressions_mutator((Node *) ntest->arg, context); - if (arg && IsA(arg, RowExpr)) + if (ntest->argisrow && arg && IsA(arg, RowExpr)) { /* * We break ROW(...) IS [NOT] NULL into separate tests on @@ -3281,8 +3281,6 @@ eval_const_expressions_mutator(Node *node, List *newargs = NIL; ListCell *l; - Assert(ntest->argisrow); - foreach(l, rarg->args) { Node *relem = (Node *) lfirst(l); @@ -3301,10 +3299,17 @@ eval_const_expressions_mutator(Node *node, return makeBoolConst(false, false); continue; } + + /* + * Else, make a scalar (argisrow == false) NullTest + * for this field. Scalar semantics are required + * because IS [NOT] NULL doesn't recurse; see comments + * in ExecEvalNullTest(). + */ newntest = makeNode(NullTest); newntest->arg = (Expr *) relem; newntest->nulltesttype = ntest->nulltesttype; - newntest->argisrow = type_is_rowtype(exprType(relem)); + newntest->argisrow = false; newargs = lappend(newargs, newntest); } /* If all the inputs were constants, result is TRUE */ |