dblink_open — opens a cursor in a remote database
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
dblink_open()
opens a cursor in a
remote database. The cursor can subsequently be manipulated with
dblink_fetch()
and dblink_close()
.
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 SELECT
statement that you wish
to execute in the remote database, for example select * 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
.
Returns status, either OK
or
ERROR
.
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.
SELECT dblink_connect('dbname=postgres options=-csearch_path='); dblink_connect ---------------- OK (1 row) SELECT dblink_open('foo', 'select proname, prosrc from pg_proc'); dblink_open ------------- OK (1 row)
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