Fix tests for generated columns dependency changes

In PG15, For GENERATED columns, all dependencies of the generation
expression are recorded as NORMAL dependencies of the column itself.
This requires CASCADE to drop generated cols with the original col.
PRE PG15, dependencies were recorded as AUTO, with which
generated columns are silently dropped with the original column.

Relevant PG commit:
cb02fcb4c95bae08adaca1202c2081cfc81a28b5

src/test/regress/expected/pg12.out

@@ -588,8 +588,12 @@ NOTICE:  renaming the new table to test_pg12.generated_stored_ref
 ROLLBACK;
 BEGIN;
   -- drop some of the columns not having "generated always as stored" expressions
-  -- this would drop generated columns too
-  ALTER TABLE generated_stored_ref DROP COLUMN col_1;
+  -- PRE PG15, this would drop generated columns too
+  -- In PG15, CASCADE option must be specified
+  -- Relevant PG Commit: cb02fcb4c95bae08adaca1202c2081cfc81a28b5
+  SET client_min_messages TO WARNING;
+  ALTER TABLE generated_stored_ref DROP COLUMN col_1 CASCADE;
+  RESET client_min_messages;
   ALTER TABLE generated_stored_ref DROP COLUMN col_4;
   -- show that undistribute_table works fine
   SELECT undistribute_table('generated_stored_ref');

src/test/regress/expected/pg15.out

@@ -168,12 +168,83 @@ SELECT * FROM sale_triggers ORDER BY 1, 2;
  truncate_trigger_xxxxxxx  | sale_newyork    | O
 (6 rows)
 
+--
+-- In PG15, For GENERATED columns, all dependencies of the generation
+-- expression are recorded as NORMAL dependencies of the column itself.
+-- This requires CASCADE to drop generated cols with the original col.
+-- Test this behavior in distributed table, specifically with
+-- undistribute_table within a transaction.
+-- Relevant PG Commit: cb02fcb4c95bae08adaca1202c2081cfc81a28b5
+--
+CREATE TABLE generated_stored_ref (
+  col_1 int,
+  col_2 int,
+  col_3 int generated always as (col_1+col_2) stored,
+  col_4 int,
+  col_5 int generated always as (col_4*2-col_1) stored
+);
+SELECT create_reference_table ('generated_stored_ref');
+ create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- populate the table
+INSERT INTO generated_stored_ref (col_1, col_4) VALUES (1,2), (11,12);
+INSERT INTO generated_stored_ref (col_1, col_2, col_4) VALUES (100,101,102), (200,201,202);
+SELECT * FROM generated_stored_ref ORDER BY 1,2,3,4,5;
+ col_1 | col_2 | col_3 | col_4 | col_5
+---------------------------------------------------------------------
+     1 |       |       |     2 |     3
+    11 |       |       |    12 |    13
+   100 |   101 |   201 |   102 |   104
+   200 |   201 |   401 |   202 |   204
+(4 rows)
+
+-- fails, CASCADE must be specified
+-- will test CASCADE inside the transcation
+ALTER TABLE generated_stored_ref DROP COLUMN col_1;
+ERROR:  cannot drop column col_1 of table generated_stored_ref because other objects depend on it
+DETAIL:  column col_3 of table generated_stored_ref depends on column col_1 of table generated_stored_ref
+column col_5 of table generated_stored_ref depends on column col_1 of table generated_stored_ref
+HINT:  Use DROP ... CASCADE to drop the dependent objects too.
+BEGIN;
+  -- drops col_1, col_3, col_5
+  ALTER TABLE generated_stored_ref DROP COLUMN col_1 CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to column col_3 of table generated_stored_ref
+drop cascades to column col_5 of table generated_stored_ref
+  ALTER TABLE generated_stored_ref DROP COLUMN col_4;
+  -- show that undistribute_table works fine
+  SELECT undistribute_table('generated_stored_ref');
+NOTICE:  creating a new table for pg15.generated_stored_ref
+NOTICE:  moving the data of pg15.generated_stored_ref
+NOTICE:  dropping the old pg15.generated_stored_ref
+NOTICE:  renaming the new table to pg15.generated_stored_ref
+ undistribute_table
+---------------------------------------------------------------------
+
+(1 row)
+
+  INSERT INTO generated_stored_ref VALUES (5);
+  SELECT * FROM generated_stored_REF ORDER BY 1;
+ col_2
+---------------------------------------------------------------------
+     5
+   101
+   201
+
+
+(5 rows)
+
+ROLLBACK;
 -- Clean up
 DROP SCHEMA pg15 CASCADE;
-NOTICE:  drop cascades to 6 other objects
+NOTICE:  drop cascades to 7 other objects
 DETAIL:  drop cascades to collation german_phonebook_test
 drop cascades to collation default_provider
 drop cascades to table sale
 drop cascades to table record_sale
 drop cascades to function record_sale()
 drop cascades to view sale_triggers
+drop cascades to table generated_stored_ref

src/test/regress/sql/pg12.sql

@@ -348,8 +348,12 @@ ROLLBACK;
 
 BEGIN;
   -- drop some of the columns not having "generated always as stored" expressions
-  -- this would drop generated columns too
-  ALTER TABLE generated_stored_ref DROP COLUMN col_1;
+  -- PRE PG15, this would drop generated columns too
+  -- In PG15, CASCADE option must be specified
+  -- Relevant PG Commit: cb02fcb4c95bae08adaca1202c2081cfc81a28b5
+  SET client_min_messages TO WARNING;
+  ALTER TABLE generated_stored_ref DROP COLUMN col_1 CASCADE;
+  RESET client_min_messages;
   ALTER TABLE generated_stored_ref DROP COLUMN col_4;
 
   -- show that undistribute_table works fine

src/test/regress/sql/pg15.sql

@@ -114,5 +114,44 @@ SELECT * FROM sale_triggers ORDER BY 1, 2;
 ALTER TRIGGER "record_sale_trigger" ON "pg15"."sale" RENAME TO "new_record_sale_trigger";
 SELECT * FROM sale_triggers ORDER BY 1, 2;
 
+--
+-- In PG15, For GENERATED columns, all dependencies of the generation
+-- expression are recorded as NORMAL dependencies of the column itself.
+-- This requires CASCADE to drop generated cols with the original col.
+-- Test this behavior in distributed table, specifically with
+-- undistribute_table within a transaction.
+-- Relevant PG Commit: cb02fcb4c95bae08adaca1202c2081cfc81a28b5
+--
+
+CREATE TABLE generated_stored_ref (
+  col_1 int,
+  col_2 int,
+  col_3 int generated always as (col_1+col_2) stored,
+  col_4 int,
+  col_5 int generated always as (col_4*2-col_1) stored
+);
+
+SELECT create_reference_table ('generated_stored_ref');
+
+-- populate the table
+INSERT INTO generated_stored_ref (col_1, col_4) VALUES (1,2), (11,12);
+INSERT INTO generated_stored_ref (col_1, col_2, col_4) VALUES (100,101,102), (200,201,202);
+SELECT * FROM generated_stored_ref ORDER BY 1,2,3,4,5;
+
+-- fails, CASCADE must be specified
+-- will test CASCADE inside the transcation
+ALTER TABLE generated_stored_ref DROP COLUMN col_1;
+
+BEGIN;
+  -- drops col_1, col_3, col_5
+  ALTER TABLE generated_stored_ref DROP COLUMN col_1 CASCADE;
+  ALTER TABLE generated_stored_ref DROP COLUMN col_4;
+
+  -- show that undistribute_table works fine
+  SELECT undistribute_table('generated_stored_ref');
+  INSERT INTO generated_stored_ref VALUES (5);
+  SELECT * FROM generated_stored_REF ORDER BY 1;
+ROLLBACK;
+
 -- Clean up
 DROP SCHEMA pg15 CASCADE;