From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 12 Jan 2005 17:32:36 +0000 (+0000)
Subject: Re-allow an untyped literal as the test expression of a CASE, ie
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=2c4451397dda7bba3bc8caa853e18cb150227bf8;p=users%2Fbernd%2Fpostgres.git

Re-allow an untyped literal as the test expression of a CASE, ie
CASE 'a' WHEN 'a' THEN 1 ELSE 2 END.  This worked in 7.4 and before
but had been broken due to premature freezing of the type of the test
expression.  Per gripe from GÄbor SzÃcs.
---

diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index ad0335b71b..ec323260c5 100644
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -646,10 +646,21 @@ transformExpr(ParseState *pstate, Node *expr)
 
 				/* transform the test expression, if any */
 				arg = transformExpr(pstate, (Node *) c->arg);
-				newc->arg = (Expr *) arg;
+
 				/* generate placeholder for test expression */
 				if (arg)
 				{
+					/*
+					 * If test expression is an untyped literal, force it to
+					 * text.  We have to do something now because we won't be
+					 * able to do this coercion on the placeholder.  This is
+					 * not as flexible as what was done in 7.4 and before,
+					 * but it's good enough to handle the sort of silly
+					 * coding commonly seen.
+					 */
+					if (exprType(arg) == UNKNOWNOID)
+						arg = coerce_to_common_type(pstate, arg,
+													TEXTOID, "CASE");
 					placeholder = makeNode(CaseTestExpr);
 					placeholder->typeId = exprType(arg);
 					placeholder->typeMod = exprTypmod(arg);
@@ -657,6 +668,8 @@ transformExpr(ParseState *pstate, Node *expr)
 				else
 					placeholder = NULL;
 
+				newc->arg = (Expr *) arg;
+
 				/* transform the list of arguments */
 				newargs = NIL;
 				typeids = NIL;