dblink_get_result — gets an async query result
dblink_get_result(text connname [, bool fail_on_error]) returns setof record
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.
connnameName of the connection to use.
fail_on_errorIf 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.
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.
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.
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)