bionic (3) dblink_get_result.3.gz

Provided by: postgresql-doc-10_10.23-0ubuntu0.18.04.2_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)