Fix crash when using COLLATE in partition bound expressions

Attempting to use a COLLATE clause with a type that it not collatable in
a partition bound expression could crash the server.  This commit fixes
the code by adding more checks similar to what is done when computing
index or partition attributes by making sure that there is a collation
iff the type is collatable.

Backpatch down to 12, as 7c079d7 introduced this problem.

Reported-by: Alexander Lakhin
Author: Dmitry Dolgov
Discussion: https://postgr.es/m/16325-809194cf742313ab@postgresql.org
Backpatch-through: 12

src/backend/parser/parse_utilcmd.c

@@ -4081,6 +4081,30 @@ transformPartitionBoundValue(ParseState *pstate, Node *val,
 	{
 		Oid			exprCollOid = exprCollation(value);
 
+		/*
+		 * Check we have a collation iff it is a collatable type.  The only
+		 * expected failures here are (1) COLLATE applied to a noncollatable
+		 * type, or (2) partition bound expression had an unresolved
+		 * collation.  But we might as well code this to be a complete
+		 * consistency check.
+		 */
+		if (type_is_collatable(colType))
+		{
+			if (!OidIsValid(exprCollOid))
+				ereport(ERROR,
+						(errcode(ERRCODE_INDETERMINATE_COLLATION),
+						 errmsg("could not determine which collation to use for partition bound expression"),
+						 errhint("Use the COLLATE clause to set the collation explicitly.")));
+		}
+		else
+		{
+			if (OidIsValid(exprCollOid))
+				ereport(ERROR,
+						(errcode(ERRCODE_DATATYPE_MISMATCH),
+						 errmsg("collations are not supported by type %s",
+								format_type_be(colType))));
+		}
+
 		if (OidIsValid(exprCollOid) &&
 			exprCollOid != DEFAULT_COLLATION_OID &&
 			exprCollOid != partCollation)

src/test/regress/expected/create_table.out

@@ -652,6 +652,12 @@ CREATE TABLE part_bogus_expr_fail PARTITION OF list_parted FOR VALUES IN (genera
 ERROR:  set-returning functions are not allowed in partition bound
 LINE 1: ...expr_fail PARTITION OF list_parted FOR VALUES IN (generate_s...
                                                              ^
+CREATE TABLE part_bogus_expr_fail PARTITION OF list_parted FOR VALUES IN ('1' collate "POSIX");
+ERROR:  collations are not supported by type integer
+CREATE TABLE part_bogus_expr_fail PARTITION OF list_parted FOR VALUES IN ((1+1) collate "POSIX");
+ERROR:  collations are not supported by type integer
+LINE 1: ...ail PARTITION OF list_parted FOR VALUES IN ((1+1) collate "P...
+                                                             ^
 -- syntax does not allow empty list of values for list partitions
 CREATE TABLE fail_part PARTITION OF list_parted FOR VALUES IN ();
 ERROR:  syntax error at or near ")"

src/test/regress/sql/create_table.sql

@@ -549,6 +549,8 @@ CREATE TABLE part_bogus_expr_fail PARTITION OF list_parted FOR VALUES IN (sum(so
 CREATE TABLE part_bogus_expr_fail PARTITION OF list_parted FOR VALUES IN (sum(1));
 CREATE TABLE part_bogus_expr_fail PARTITION OF list_parted FOR VALUES IN ((select 1));
 CREATE TABLE part_bogus_expr_fail PARTITION OF list_parted FOR VALUES IN (generate_series(4, 6));
+CREATE TABLE part_bogus_expr_fail PARTITION OF list_parted FOR VALUES IN ('1' collate "POSIX");
+CREATE TABLE part_bogus_expr_fail PARTITION OF list_parted FOR VALUES IN ((1+1) collate "POSIX");
 
 -- syntax does not allow empty list of values for list partitions
 CREATE TABLE fail_part PARTITION OF list_parted FOR VALUES IN ();