Change plpgsql's cast cache to consider source typmod as significant.

I had thought that there was no need to maintain separate cache entries
for different source typmods, but further experimentation shows that there
is an advantage to doing so in some cases.  In particular, if a domain has
a typmod (say, "CREATE DOMAIN d AS numeric(20,0)"), failing to notice the
source typmod leads to applying a length-coercion step even when the
source has the correct typmod.

Author: tglsfdc

src/pl/plpgsql/src/pl_exec.c

@@ -57,6 +57,7 @@ typedef struct
 	/* NB: we assume this struct contains no padding bytes */
 	Oid			srctype;		/* source type for cast */
 	Oid			dsttype;		/* destination type for cast */
+	int32		srctypmod;		/* source typmod for cast */
 	int32		dsttypmod;		/* destination typmod for cast */
 } plpgsql_CastHashKey;
 
@@ -231,7 +232,7 @@ static Datum exec_cast_value(PLpgSQL_execstate *estate,
 				Oid valtype, int32 valtypmod,
 				Oid reqtype, int32 reqtypmod);
 static ExprState *get_cast_expression(PLpgSQL_execstate *estate,
-					Oid srctype, Oid dsttype, int32 dsttypmod);
+				 Oid srctype, int32 srctypmod, Oid dsttype, int32 dsttypmod);
 static void exec_init_tuple_store(PLpgSQL_execstate *estate);
 static void exec_set_found(PLpgSQL_execstate *estate, bool state);
 static void plpgsql_create_econtext(PLpgSQL_execstate *estate);
@@ -5733,7 +5734,9 @@ exec_cast_value(PLpgSQL_execstate *estate,
 	{
 		ExprState  *cast_expr;
 
-		cast_expr = get_cast_expression(estate, valtype, reqtype, reqtypmod);
+		cast_expr = get_cast_expression(estate,
+										valtype, valtypmod,
+										reqtype, reqtypmod);
 		if (cast_expr)
 		{
 			ExprContext *econtext = estate->eval_econtext;
@@ -5769,7 +5772,7 @@ exec_cast_value(PLpgSQL_execstate *estate,
  */
 static ExprState *
 get_cast_expression(PLpgSQL_execstate *estate,
-					Oid srctype, Oid dsttype, int32 dsttypmod)
+				  Oid srctype, int32 srctypmod, Oid dsttype, int32 dsttypmod)
 {
 	HTAB	   *cast_hash = estate->func->cast_hash;
 	plpgsql_CastHashKey cast_key;
@@ -5799,6 +5802,7 @@ get_cast_expression(PLpgSQL_execstate *estate,
 	/* Look for existing entry */
 	cast_key.srctype = srctype;
 	cast_key.dsttype = dsttype;
+	cast_key.srctypmod = srctypmod;
 	cast_key.dsttypmod = dsttypmod;
 	cast_entry = (plpgsql_CastHashEntry *) hash_search(cast_hash,
 													   (void *) &cast_key,
@@ -5815,7 +5819,7 @@ get_cast_expression(PLpgSQL_execstate *estate,
 	 */
 	placeholder = makeNode(CaseTestExpr);
 	placeholder->typeId = srctype;
-	placeholder->typeMod = -1;
+	placeholder->typeMod = srctypmod;
 	placeholder->collation = get_typcollation(srctype);
 	if (OidIsValid(estate->func->fn_input_collation) &&
 		OidIsValid(placeholder->collation))