code: func PgGetExpr(db XODB, v0 pgtypes.PgNodeTree, v1 pgtypes.Oid, v2 pgtypes.PgNodeTree, v3 pgtypes.Oid, v4 bool) (string, error) {
  	var err error
  
  	// sql query
  	const sqlstr = `SELECT pg_catalog.pg_get_expr($1, $2, $3, $4, $5)`
  
  	// run query
  	var ret string
  	XOLog(sqlstr, v0, v1, v2, v3, v4)
  	err = db.QueryRow(sqlstr, v0, v1, v2, v3, v4).Scan(&ret)
  	if err != nil {
  		return "", err
  	}
  
  	return ret, nil
  }
docs: // PgGetExpr calls the stored procedure 'pg_catalog.pg_get_expr(pg_node_tree, oid, pg_node_tree, oid, boolean) text' on db.