[#23163] YSQL: pg_partman: make 'apply_publications' idempotent

Summary:
Currently transactional DDL is not supported in YugabyteDB . Due to which if any procedure or function which is performing multiple DDLs in a
transactional context can lead to issue of some DDLs getting executed and committed even if stored procedure failed due to some exception
while running stored procedure or Postgres backend process or tserver process kill.

This diff makes apply_publications.sql function idempotent such that multiple calls to don't have any additional consequences.

 - This function is used to add child tables to publication
 - Changes done
   - Added a check to not invoke ALTER PUBLICATION <publication> ADD table <child_table> if child_table is already part of the publication.
Jira: DB-12101

Test Plan: jenkins: compile only

Reviewers: skumar, jason, hsunder

Reviewed By: jason

Subscribers: yql

Differential Revision: https://phorge.dev.yugabyte.com/D36677

src/postgres/third-party-extensions/pg_partman/sql/functions/apply_publications.sql

@@ -5,6 +5,7 @@ DECLARE
     v_publications      text[];
     v_row               record;
     v_sql               text;
+    yb_v_table_exists   boolean;
 BEGIN
 /*
 * Function to ATLER PUBLICATION ... ADD TABLE to support logical replication
@@ -18,9 +19,23 @@ WHERE c.parent_table = p_parent_table;
 FOR v_row IN
     SELECT pubname FROM unnest(v_publications) AS pubname
 LOOP
-    v_sql = format('ALTER PUBLICATION %I ADD TABLE %I.%I', v_row.pubname, p_child_schema, p_child_tablename);
-    RAISE DEBUG '%', v_sql;
-    EXECUTE v_sql;
+
+    SELECT EXISTS (
+        SELECT 1
+        FROM pg_publication_rel pr
+        JOIN pg_class c ON pr.prrelid = c.oid
+        JOIN pg_namespace n ON c.relnamespace = n.oid
+        JOIN pg_publication p ON pr.prpubid = p.oid
+        WHERE c.relname = p_child_tablename
+        AND n.nspname = p_child_schema
+        AND p.pubname = v_row.pubname
+    ) INTO yb_v_table_exists;
+
+    IF NOT yb_v_table_exists THEN
+        v_sql = format('ALTER PUBLICATION %I ADD TABLE %I.%I', v_row.pubname, p_child_schema, p_child_tablename);
+        RAISE DEBUG '%', v_sql;
+        EXECUTE v_sql;
+    END IF;
 END LOOP;
 
 END;