diff options
| 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 | d243bf77c2d3888fb263c55317c2453cb437d1de (patch) | |
| tree | 6ec5799f24acb9168f1f73ccc7da84fd87cb662d /src/backend/optimizer/util/clauses.c | |
| parent | b1fa6c0eb9fadc9eada014227a67eadfec936960 (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 | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c index e7bfc38d566..667e682e2d1 100644 --- a/src/backend/optimizer/util/clauses.c +++ b/src/backend/optimizer/util/clauses.c @@ -2970,7 +2970,7 @@ 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 its @@ -2981,8 +2981,6 @@ eval_const_expressions_mutator(Node *node, List *newargs = NIL; ListCell *l; - Assert(ntest->argisrow); - foreach(l, rarg->args) { Node *relem = (Node *) lfirst(l); @@ -3001,10 +2999,16 @@ 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 */ |