dblink_open
dblink_open
dblink_open - opens a cursor in a remote database
Synopsis
dblink_open(text cursorname, text sql [, bool fail_on_error]) returns text dblink_open(text connname, text cursorname, text sql [, bool fail_on_error]) returns text
Description
dblink_open()
opens a cursor in a remote database.
The cursor can subsequently be manipulated with
dblink_fetch()
and
dblink_close()
.
Arguments
-
connname -
Name of the connection to use; omit this parameter to use the unnamed connection.
-
cursorname -
The name to assign to this cursor.
-
sql -
The
SELECTstatement that you wish to execute in the remote database, for exampleselect * from pg_class. -
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's return value is set to
ERROR.
Return Value
Returns status, either
OK
or
ERROR
.
Notes
Since a cursor can only persist within a transaction,
dblink_open
starts an explicit transaction block
(
BEGIN
) on the remote side, if the remote side was
not already within a transaction. This transaction will be
closed again when the matching
dblink_close
is
executed. Note that if
you use
dblink_exec
to change data between
dblink_open
and
dblink_close
,
and then an error occurs or you use
dblink_disconnect
before
dblink_close
, your change
will be
lost
because the transaction will be aborted.
Examples
SELECT dblink_connect('dbname=postgres');
dblink_connect
----------------
OK
(1 row)
SELECT dblink_open('foo', 'select proname, prosrc from pg_proc');
dblink_open
-------------
OK
(1 row)