Provided by: postgresql-doc-12_12.2-4_all bug

NAME

       dblink_get_result - gets an async query result

SYNOPSIS

       dblink_get_result(text connname [, bool fail_on_error]) returns setof record

DESCRIPTION

       dblink_get_result collects the results of an asynchronous query previously sent with
       dblink_send_query. If the query is not already completed, dblink_get_result will wait
       until it is.

ARGUMENTS

       connname
           Name of the connection to use.

       fail_on_error
           If true (the default when omitted) then an error thrown on the remote side of the
           connection causes an error to also be thrown locally. If false, the remote error is
           locally reported as a NOTICE, and the function returns no rows.

RETURN VALUE

       For an async query (that is, a SQL statement returning rows), the function returns the
       row(s) produced by the query. To use this function, you will need to specify the expected
       set of columns, as previously discussed for dblink.

       For an async command (that is, a SQL statement not returning rows), the function returns a
       single row with a single text column containing the command's status string. It is still
       necessary to specify that the result will have a single text column in the calling FROM
       clause.

NOTES

       This function must be called if dblink_send_query returned 1. It must be called once for
       each query sent, and one additional time to obtain an empty set result, before the
       connection can be used again.

       When using dblink_send_query and dblink_get_result, dblink fetches the entire remote query
       result before returning any of it to the local query processor. If the query returns a
       large number of rows, this can result in transient memory bloat in the local session. It
       may be better to open such a query as a cursor with dblink_open and then fetch a
       manageable number of rows at a time. Alternatively, use plain dblink(), which avoids
       memory bloat by spooling large result sets to disk.

EXAMPLES

           contrib_regression=# SELECT dblink_connect('dtest1', 'dbname=contrib_regression');
            dblink_connect
           ----------------
            OK
           (1 row)

           contrib_regression=# SELECT * FROM
           contrib_regression-# dblink_send_query('dtest1', 'select * from foo where f1 < 3') AS t1;
            t1
           ----
             1
           (1 row)

           contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]);
            f1 | f2 |     f3
           ----+----+------------
             0 | a  | {a0,b0,c0}
             1 | b  | {a1,b1,c1}
             2 | c  | {a2,b2,c2}
           (3 rows)

           contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]);
            f1 | f2 | f3
           ----+----+----
           (0 rows)

           contrib_regression=# SELECT * FROM
           contrib_regression-# dblink_send_query('dtest1', 'select * from foo where f1 < 3; select * from foo where f1 > 6') AS t1;
            t1
           ----
             1
           (1 row)

           contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]);
            f1 | f2 |     f3
           ----+----+------------
             0 | a  | {a0,b0,c0}
             1 | b  | {a1,b1,c1}
             2 | c  | {a2,b2,c2}
           (3 rows)

           contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]);
            f1 | f2 |      f3
           ----+----+---------------
             7 | h  | {a7,b7,c7}
             8 | i  | {a8,b8,c8}
             9 | j  | {a9,b9,c9}
            10 | k  | {a10,b10,c10}
           (4 rows)

           contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]);
            f1 | f2 | f3
           ----+----+----
           (0 rows)