Remove obsolete check in gpexpand for dropped columns.

The way dropped columns are handled in ALTER TABLE was changed back in
2017, commit 62d66c06, but gpexpand didn't get the memo. Dropped columns
of custom datatypes no longer pose any problems.
Reviewed-by: NVenkatesh Raghavan <vraghavan@pivotal.io>

gpMgmt/bin/gpexpand

@@ -351,36 +351,6 @@ WHERE status = '%s'
                          'EXPANSION STARTED',
                          start_status, undone_status)
 
-unalterable_table_sql = """
-SELECT
-    current_database() AS database,
-    pg_catalog.quote_ident(nspname) || '.' ||
-    pg_catalog.quote_ident(relname) AS table,
-    attnum,
-    attlen,
-    attbyval,
-    attstorage,
-    attalign,
-    atttypmod,
-    attndims,
-    reltoastrelid != 0 AS istoasted
-FROM
-    pg_catalog.pg_attribute,
-    pg_catalog.pg_class,
-    pg_catalog.pg_namespace
-WHERE
-    attisdropped
-    AND attnum >= 0
-    AND attrelid = pg_catalog.pg_class.oid
-    AND relnamespace = pg_catalog.pg_namespace.oid
-    AND (attlen, attbyval, attalign, attstorage) NOT IN
-        (SELECT typlen, typbyval, typalign, typstorage
-        FROM pg_catalog.pg_type
-        WHERE typisdefined AND typtype='b' )
-ORDER BY
-    attrelid, attnum
-"""
-
 has_unique_index_sql = """
 SELECT
     current_database() || '.' || pg_catalog.quote_ident(nspname) || '.' || pg_catalog.quote_ident(relname) AS table
@@ -1025,46 +995,6 @@ Set PGDATABASE or use the -D option to specify the correct database to use.""" %
 
         return True
 
-    def validate_unalterable_tables(self):
-        conn = None
-        unalterable_tables = []
-
-        try:
-            conn = dbconn.connect(self.dburl, utility=True, encoding='UTF8')
-            databases = catalog.getDatabaseList(conn)
-            conn.close()
-
-            tempurl = copy.deepcopy(self.dburl)
-            for db in databases:
-                if db[0] == 'template0':
-                    continue
-                self.logger.info('Checking database %s for unalterable tables...' % db[0].decode('utf-8'))
-                tempurl.pgdb = db[0]
-                conn = dbconn.connect(tempurl, utility=True, encoding='UTF8')
-                cursor = dbconn.execSQL(conn, unalterable_table_sql)
-                for row in cursor:
-                    unalterable_tables.append(row)
-                cursor.close()
-                conn.close()
-
-        except DatabaseError, ex:
-            if self.options.verbose:
-                logger.exception(ex)
-            logger.error('Failed to check for unalterable tables.')
-            if conn: conn.close()
-            raise ex
-
-        if len(unalterable_tables) > 0:
-            self.logger.error('The following tables cannot be altered because they contain')
-            self.logger.error('dropped columns of user defined types:')
-            for t in unalterable_tables:
-                self.logger.error('\t%s.%s' % (t[0].decode('utf-8'), t[1].decode('utf-8')))
-            self.logger.error('Please consult the documentation for instructions on how to')
-            self.logger.error('correct this issue, then run gpexpand again')
-            return False
-
-        return True
-
     def check_unique_indexes(self):
         """ Checks if there are tables with unique indexes.
         Returns true if unique indexes exist"""
@@ -2460,8 +2390,6 @@ def main(options, args, parser):
             logger.info('If you want to expand again, run gpexpand -c to remove')
             logger.info('the gpexpand schema and begin a new expansion')
         elif gpexpand_db_status is None and gpexpand_file_status is None and options.filename:
-            if not _gp_expand.validate_unalterable_tables():
-                raise ValidationError()
             if _gp_expand.check_unique_indexes():
                 logger.warn("Tables with unique indexes exist.  Until these tables are successfully")
                 logger.warn("redistributed, unique constraints may be violated.  For more information")

gpdb-doc/dita/admin_guide/expand/expand-planning.xml

@@ -427,16 +427,6 @@
           </ul></p>
       </body>
     </topic>
-    <topic id="topic15" xml:lang="en">
-      <title>Redistributing Tables with User-Defined Data Types</title>
-      <body>
-        <p>You cannot perform redistribution with the expansion utility on tables with dropped
-          columns of user-defined data types. To redistribute tables with dropped columns of
-          user-defined types, first re-create the table using <codeph>CREATE TABLE AS
-            SELECT</codeph>. After this process removes the dropped columns, redistribute the table
-          with <codeph>gpexpand</codeph>.</p>
-      </body>
-    </topic>
     <topic id="topic16" xml:lang="en">
       <title>Redistributing Partitioned Tables</title>
       <body>