Fix failure when creating cloned indexes for a partition

When using CREATE TABLE for a new partition, the partitioned indexes of
the parent are created automatically in a fashion similar to LIKE
INDEXES.  The new partition and its parent use a mapping for attribute
numbers for this operation, and while the mapping was correctly built,
its length was defined as the number of attributes of the newly-created
child, and not the parent.  If the parent includes dropped columns, this
could cause failures.

This is wrong since 8b08f7d which has introduced the concept of
partitioned indexes, so backpatch down to 11.

Reported-by: Wyatt Alt
Author: Michael Paquier
Reviewed-by: Amit Langote
Discussion: https://postgr.es/m/CAGem3qCcRmhbs4jYMkenYNfP2kEusDXvTfw-q+eOhM0zTceG-g@mail.gmail.com
Backpatch-through: 11

src/backend/commands/tablecmds.c

@@ -961,7 +961,7 @@ DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId,
 												gettext_noop("could not convert row type"));
 			idxstmt =
 				generateClonedIndexStmt(NULL, RelationGetRelid(rel), idxRel,
-										attmap, RelationGetDescr(rel)->natts,
+										attmap, RelationGetDescr(parent)->natts,
 										&constraintOid);
 			DefineIndex(RelationGetRelid(rel),
 						idxstmt,

src/test/regress/expected/create_table.out

@@ -1006,3 +1006,52 @@ CONTEXT:  SQL statement "create table tab_part_create_1 partition of tab_part_cr
 PL/pgSQL function func_part_create() line 3 at EXECUTE
 drop table tab_part_create;
 drop function func_part_create();
+-- tests of column drop with partition tables and indexes using
+-- predicates and expressions.
+create table part_column_drop (
+  useless_1 int,
+  id int,
+  useless_2 int,
+  d int,
+  b int,
+  useless_3 int
+) partition by range (id);
+alter table part_column_drop drop column useless_1;
+alter table part_column_drop drop column useless_2;
+alter table part_column_drop drop column useless_3;
+create index part_column_drop_b_pred on part_column_drop(b) where b = 1;
+create index part_column_drop_b_expr on part_column_drop((b = 1));
+create index part_column_drop_d_pred on part_column_drop(d) where d = 2;
+create index part_column_drop_d_expr on part_column_drop((d = 2));
+create table part_column_drop_1_10 partition of
+  part_column_drop for values from (1) to (10);
+\d part_column_drop
+          Table "public.part_column_drop"
+ Column |  Type   | Collation | Nullable | Default 
+--------+---------+-----------+----------+---------
+ id     | integer |           |          | 
+ d      | integer |           |          | 
+ b      | integer |           |          | 
+Partition key: RANGE (id)
+Indexes:
+    "part_column_drop_b_expr" btree ((b = 1))
+    "part_column_drop_b_pred" btree (b) WHERE b = 1
+    "part_column_drop_d_expr" btree ((d = 2))
+    "part_column_drop_d_pred" btree (d) WHERE d = 2
+Number of partitions: 1 (Use \d+ to list them.)
+
+\d part_column_drop_1_10
+       Table "public.part_column_drop_1_10"
+ Column |  Type   | Collation | Nullable | Default 
+--------+---------+-----------+----------+---------
+ id     | integer |           |          | 
+ d      | integer |           |          | 
+ b      | integer |           |          | 
+Partition of: part_column_drop FOR VALUES FROM (1) TO (10)
+Indexes:
+    "part_column_drop_1_10_b_idx" btree (b) WHERE b = 1
+    "part_column_drop_1_10_d_idx" btree (d) WHERE d = 2
+    "part_column_drop_1_10_expr_idx" btree ((b = 1))
+    "part_column_drop_1_10_expr_idx1" btree ((d = 2))
+
+drop table part_column_drop;

src/test/regress/sql/create_table.sql

@@ -814,3 +814,26 @@ create trigger trig_part_create before insert on tab_part_create
 insert into tab_part_create values (1);
 drop table tab_part_create;
 drop function func_part_create();
+
+-- tests of column drop with partition tables and indexes using
+-- predicates and expressions.
+create table part_column_drop (
+  useless_1 int,
+  id int,
+  useless_2 int,
+  d int,
+  b int,
+  useless_3 int
+) partition by range (id);
+alter table part_column_drop drop column useless_1;
+alter table part_column_drop drop column useless_2;
+alter table part_column_drop drop column useless_3;
+create index part_column_drop_b_pred on part_column_drop(b) where b = 1;
+create index part_column_drop_b_expr on part_column_drop((b = 1));
+create index part_column_drop_d_pred on part_column_drop(d) where d = 2;
+create index part_column_drop_d_expr on part_column_drop((d = 2));
+create table part_column_drop_1_10 partition of
+  part_column_drop for values from (1) to (10);
+\d part_column_drop
+\d part_column_drop_1_10
+drop table part_column_drop;