[YSQL]: #2226 Added a comment to ALTER COLUMN add/set/drop identity t…

…est.

Summary: Add missing comments.

Test Plan: ./yb_build.sh --java-test org.yb.pgsql.TestPgRegressPgMiscIndependent

Reviewers: neha

Reviewed By: neha

Subscribers: yql

Differential Revision: https://phabricator.dev.yugabyte.com/D7222

src/postgres/src/test/regress/expected/yb_pg_identity.out

@@ -10,6 +10,7 @@ CREATE TABLE itest3 (a smallint generated by default as identity (start with 7 i
 ALTER TABLE itest3 ALTER COLUMN a ADD GENERATED ALWAYS AS IDENTITY;  -- error
 ERROR:  column "a" of relation "itest3" is already an identity column
 -- drop extra sequence created by alter table
+-- this is needed due to #1383 and can be removed after the issue is fixed.
 DROP SEQUENCE itest3_a_seq1;
 SELECT table_name, column_name, column_default, is_nullable, is_identity, identity_generation, identity_start, identity_increment, identity_maximum, identity_minimum, identity_cycle FROM information_schema.columns WHERE table_name LIKE 'itest_' ORDER BY 1, 2;
  table_name | column_name | column_default | is_nullable | is_identity | identity_generation | identity_start | identity_increment |  identity_maximum   | identity_minimum | identity_cycle 

src/postgres/src/test/regress/sql/yb_pg_identity.sql

@@ -7,6 +7,7 @@ CREATE TABLE itest2 (a bigint generated always as identity, b text);
 CREATE TABLE itest3 (a smallint generated by default as identity (start with 7 increment by 5), b text);
 ALTER TABLE itest3 ALTER COLUMN a ADD GENERATED ALWAYS AS IDENTITY;  -- error
 -- drop extra sequence created by alter table
+-- this is needed due to #1383 and can be removed after the issue is fixed.
 DROP SEQUENCE itest3_a_seq1;
 
 SELECT table_name, column_name, column_default, is_nullable, is_identity, identity_generation, identity_start, identity_increment, identity_maximum, identity_minimum, identity_cycle FROM information_schema.columns WHERE table_name LIKE 'itest_' ORDER BY 1, 2;