Postgres-XC 1.0.2 Documentation
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dblink_open

Name

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

Note: The following description applies only to Postgres-XC

dblink module has not been tested with Postges-XC yet. Although there're no reason that dblink does not run in Postgres-XC, the development team leaves the test and the use of this module entirely to users.

This section is identical to the corresponding PostgreSQL reference manual.

Note: The following description applies only to PostgreSQL

dblink_open() opens a cursor in a remote database. The cursor can subsequently be manipulated with dblink_fetch() and dblink_close().

Arguments

Note: The following description applies only to PostgreSQL

conname

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.

Return Value

Note: The following description applies only to PostgreSQL

Returns status, either OK or ERROR.

Notes

Note: The following description applies only to PostgreSQL

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.

Example

Note: The following description applies only to PostgreSQL

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)
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