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Make eval_const_expressions() preserve typmod when simplifying something like

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null::char(3) to a simple Const node.  (It already worked for non-null values,
but not when we skipped evaluation of a strict coercion function.)  This
prevents loss of typmod knowledge in situations such as exhibited in bug
#3598.  Unfortunately there seems no good way to fix that bug in 8.1 and 8.2,
because they simply don't carry a typmod for a plain Const node.

In passing I made all the other callers of makeNullConst supply "real" typmod
values too, though I think it probably doesn't matter anywhere else.
This commit is contained in:
Tom Lane
2007-09-06 17:31:58 +00:00
parent 190df8a4cf
commit f8942f4a15
10 changed files with 31 additions and 26 deletions
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6
src/backend/optimizer/util/clauses.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.248 2007/09/03 00:39:15 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.249 2007/09/06 17:31:58 tgl Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
@ -2265,7 +2265,7 @@ eval_const_expressions_mutator(Node *node,
/* If all the arguments were constant null, the result is just null */
if (newargs == NIL)
return (Node *) makeNullConst(coalesceexpr->coalescetype);
return (Node *) makeNullConst(coalesceexpr->coalescetype, -1);
newcoalesce = makeNode(CoalesceExpr);
newcoalesce->coalescetype = coalesceexpr->coalescetype;
@ -2833,7 +2833,7 @@ evaluate_function(Oid funcid, Oid result_type, int32 result_typmod, List *args,
* function is not otherwise immutable.
*/
if (funcform->proisstrict && has_null_input)
return (Expr *) makeNullConst(result_type);
return (Expr *) makeNullConst(result_type, result_typmod);
/*
* Otherwise, can simplify only if all inputs are constants. (For a