Postgres Import Table Function

import_table.sql

CREATE OR REPLACE FUNCTION "my_schema"."import_table" (fdw_server text, tablename text, where_filter text)  RETURNS bigint
  VOLATILE
AS $body$
DECLARE
  v_fdw_schema TEXT;
  v_fdw_tablename TEXT;
  v_col_def TEXT;
  v_query TEXT;
  v_schema_name TEXT;
  v_table_name TEXT;
  v_row_cnt BIGINT;
  BEGIN
  
  v_schema_name:=substring(tablename,0,position('.' in tablename));
  v_table_name:=substring(tablename,position('.' in tablename)+1);
  v_fdw_schema:=v_schema_name ||'_fdw';
  v_fdw_tablename:=v_fdw_schema || '.' || v_table_name;
  
  v_query:='CREATE SCHEMA IF NOT EXISTS '|| v_fdw_schema;
  RAISE INFO '%', v_query;
  EXECUTE v_query;
  
  v_query:='DROP FOREIGN TABLE IF EXISTS '|| v_fdw_schema || '.' || v_table_name ||' CASCADE';
  RAISE INFO '%', v_query;
  EXECUTE v_query;
  
  v_query:='IMPORT FOREIGN SCHEMA  '|| v_schema_name || ' LIMIT TO (' || v_table_name ||') FROM SERVER ' || fdw_server || ' INTO ' || v_fdw_schema;
  RAISE INFO '%', v_query;
  EXECUTE v_query;
  
  v_query:='CREATE SCHEMA IF NOT EXISTS '|| v_schema_name;
  RAISE INFO '%', v_query;
  EXECUTE v_query;
  
  v_query:='CREATE TABLE IF NOT EXISTS '|| tablename ||'  AS SELECT * FROM '|| v_fdw_tablename ||' WHERE 1=0';
  RAISE INFO '%', v_query;
  EXECUTE v_query;
  
  v_col_def:= STRING_AGG(column_name,',')
        FROM information_schema.columns
        WHERE table_catalog IN (SELECT current_database())
        AND table_schema = v_schema_name
        AND table_name   = v_table_name;
  
  v_query:='DELETE FROM '|| tablename ||'; INSERT INTO '|| tablename ||' ('||v_col_def||') SELECT '||v_col_def||' FROM ' || v_fdw_tablename || ' ' || where_filter;
  RAISE INFO '%', v_query;
  EXECUTE v_query;
  GET DIAGNOSTICS v_row_cnt = ROW_COUNT;
  
  v_query:='DROP SCHEMA IF EXISTS '|| v_fdw_schema || ' CASCADE';
  RAISE INFO '%', v_query;
  EXECUTE v_query;
  
  RETURN v_row_cnt;
  
  END;
$body$ LANGUAGE plpgsql