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.
Name of the connection to use.
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.
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)