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ForeignServerCreation.md

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TDS Foreign data wrapper

  • Author: Geoff Montee
  • Name: tds_fdw
  • File: tds_fdw/ForeignServerCreation.md

Creating a Foreign Server

Options

Foreign server parameters accepted:

  • servername

Required: Yes

Default: 127.0.0.1

The servername, address or hostname of the foreign server server.

This can be a DSN, as specified in freetds.conf. See FreeTDS name lookup.

You can set this option to a comma separated list of server names, then each server is tried until the first connection succeeds.
This is useful for automatic fail-over to a secondary server.

  • port

Required: No

The port of the foreign server. This is optional. Instead of providing a port here, it can be specified in freetds.conf (if servername is a DSN).

  • database

Required: No

The database to connect to for this server.

  • dbuse

Required: No

Default: 0

This option tells tds_fdw to connect directly to database if dbuse is 0. If dbuse is not 0, tds_fdw will connect to the server's default database, and then select database by calling DB-Library's dbuse() function.

For Azure, dbuse currently needs to be set to 0.

  • language

Required: No

The language to use for messages and the locale to use for date formats. FreeTDS may default to us_english on most systems. You can probably also change this in freetds.conf.

For information related to this for MS SQL Server, see SET LANGUAGE in MS SQL Server.

For information related to Sybase ASE, see Sybase ASE login options and SET LANGUAGE in Sybase ASE.

  • character_set

Required: No

The client character set to use for the connection, if you need to set this for some reason.

For TDS protocol versions 7.0+, the connection always uses UCS-2, so this parameter does nothing in those cases. See Localization and TDS 7.0.

  • tds_version

Required: No

The version of the TDS protocol to use for this server. See Choosing a TDS protocol version and History of TDS Versions.

  • msg_handler

Required: No

Default: blackhole

The function used for the TDS message handler. Options are "notice" and "blackhole." With the "notice" option, TDS messages are turned into PostgreSQL notices. With the "blackhole" option, TDS messages are ignored.

  • fdw_startup_cost

Required: No

A cost that is used to represent the overhead of using this FDW used in query planning.

  • fdw_tuple_cost

Required: No

A cost that is used to represent the overhead of fetching rows from this server used in query planning.

  • sqlserver_ansi_mode

Required: No

This option is supported for SQL Server only. The default is "false". Setting this to "true" will enable the following server-side settings after a successful connection to the foreign server:

* CONCAT_NULLS_YIELDS_NULL ON
* ANSI_NULLS ON
* ANSI_WARNINGS ON
* QUOTED_IDENTIFIER ON
* ANSI_PADDING ON
* ANSI_NULL_DFLT_ON ON

Those parameters in summary are comparable to the SQL Server option ANSI_DEFAULTS. In contrast, sqlserver_ansi_mode currently does not activate the following options:

* CURSOR_CLOSE_ON_COMMIT
* IMPLICIT_TRANSACTIONS

This follows the behavior of the native ODBC and OLEDB driver for SQL Servers, which explicitly turn them OFF if not configured otherwise.

Foreign table parameters accepted in server definition:

Some foreign table options can also be set at the server level. Those include:

  • use_remote_estimate
  • row_estimate_method

Example

CREATE SERVER mssql_svr
	FOREIGN DATA WRAPPER tds_fdw
	OPTIONS (servername '127.0.0.1', port '1433', database 'tds_fdw_test', tds_version '7.1');