dblink_fetch
dblink_fetch
dblink_fetch - returns rows from an open cursor in a remote database
Synopsis
dblink_fetch(text cursorname, int howmany [, bool fail_on_error]) returns setof record dblink_fetch(text connname, text cursorname, int howmany [, bool fail_on_error]) returns setof record
Description
dblink_fetch
fetches rows from a cursor previously
established by
dblink_open
.
Arguments
-
connname -
Name of the connection to use; omit this parameter to use the unnamed connection.
-
cursorname -
The name of the cursor to fetch from.
-
howmany -
The maximum number of rows to retrieve. The next
howmanyrows are fetched, starting at the current cursor position, moving forward. Once the cursor has reached its end, no more rows are produced. -
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
The function returns the row(s) fetched from the cursor. To use this
function, you will need to specify the expected set of columns,
as previously discussed for
dblink
.
Notes
On a mismatch between the number of return columns specified in the
FROM
clause, and the actual number of columns returned by the
remote cursor, an error will be thrown. In this event, the remote cursor
is still advanced by as many rows as it would have been if the error had
not occurred. The same is true for any other error occurring in the local
query after the remote
FETCH
has been done.
Examples
SELECT dblink_connect('dbname=postgres options=-csearch_path=');
dblink_connect
----------------
OK
(1 row)
SELECT dblink_open('foo', 'select proname, prosrc from pg_proc where proname like ''bytea%''');
dblink_open
-------------
OK
(1 row)
SELECT * FROM dblink_fetch('foo', 5) AS (funcname name, source text);
funcname | source
----------+----------
byteacat | byteacat
byteacmp | byteacmp
byteaeq | byteaeq
byteage | byteage
byteagt | byteagt
(5 rows)
SELECT * FROM dblink_fetch('foo', 5) AS (funcname name, source text);
funcname | source
-----------+-----------
byteain | byteain
byteale | byteale
bytealike | bytealike
bytealt | bytealt
byteane | byteane
(5 rows)
SELECT * FROM dblink_fetch('foo', 5) AS (funcname name, source text);
funcname | source
------------+------------
byteanlike | byteanlike
byteaout | byteaout
(2 rows)
SELECT * FROM dblink_fetch('foo', 5) AS (funcname name, source text);
funcname | source
----------+--------
(0 rows)