Pass collation to makeConst() instead of looking it up internally.

In nearly all cases, the caller already knows the correct collation, and
in a number of places, the value the caller has handy is more correct than
the default for the type would be.  (In particular, this patch makes it
significantly less likely that eval_const_expressions will result in
changing the exposed collation of an expression.)  So an internal lookup
is both expensive and wrong.

1 files changed, 37 insertions, 3 deletions

diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 33f300bfea2..c757fcb424f 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -1686,6 +1686,7 @@ scalararraysel(PlannerInfo *root,
 	Node	   *leftop;
 	Node	   *rightop;
 	Oid			nominal_element_type;
+	Oid			nominal_element_collation;
 	RegProcedure oprsel;
 	FmgrInfo	oprselproc;
 	Selectivity s1;
@@ -1712,6 +1713,8 @@ scalararraysel(PlannerInfo *root,
 	nominal_element_type = get_base_element_type(exprType(rightop));
 	if (!OidIsValid(nominal_element_type))
 		return (Selectivity) 0.5;		/* probably shouldn't happen */
+	/* get nominal collation, too, for generating constants */
+	nominal_element_collation = exprCollation(rightop);
 
 	/* look through any binary-compatible relabeling of rightop */
 	rightop = strip_array_coercion(rightop);
@@ -1759,6 +1762,7 @@ scalararraysel(PlannerInfo *root,
 			args = list_make2(leftop,
 							  makeConst(nominal_element_type,
 										-1,
+										nominal_element_collation,
 										elmlen,
 										elem_values[i],
 										elem_nulls[i],
@@ -5616,9 +5620,39 @@ static Const *
 string_to_const(const char *str, Oid datatype)
 {
 	Datum		conval = string_to_datum(str, datatype);
+	Oid			collation;
+	int			constlen;
 
-	return makeConst(datatype, -1,
-					 ((datatype == NAMEOID) ? NAMEDATALEN : -1),
+	/*
+	 * We only need to support a few datatypes here, so hard-wire properties
+	 * instead of incurring the expense of catalog lookups.
+	 */
+	switch (datatype)
+	{
+		case TEXTOID:
+		case VARCHAROID:
+		case BPCHAROID:
+			collation = DEFAULT_COLLATION_OID;
+			constlen = -1;
+			break;
+
+		case NAMEOID:
+			collation = InvalidOid;
+			constlen = NAMEDATALEN;
+			break;
+
+		case BYTEAOID:
+			collation = InvalidOid;
+			constlen = -1;
+			break;
+
+		default:
+			elog(ERROR, "unexpected datatype in string_to_const: %u",
+				 datatype);
+			return NULL;
+	}
+
+	return makeConst(datatype, -1, collation, constlen,
 					 conval, false, false);
 }
 
@@ -5635,7 +5669,7 @@ string_to_bytea_const(const char *str, size_t str_len)
 	SET_VARSIZE(bstr, VARHDRSZ + str_len);
 	conval = PointerGetDatum(bstr);
 
-	return makeConst(BYTEAOID, -1, -1, conval, false, false);
+	return makeConst(BYTEAOID, -1, InvalidOid, -1, conval, false, false);
 }
 
 /*-------------------------------------------------------------------------