Database Reference
In-Depth Information
This example includes only the most basic options for the foreign table. By default, all
PostgreSQL foreign tables are editable/updatable, unless of course the remote account
you used doesn't have update access to that table. The updatable setting is a Boolean
setting that can be changed at the foreign table or the foreign server definition. For
example, to make your table read-only, execute:
ALTER FOREIGN TABLE ft_facts OPTIONS ( ADD updatable 'false' );
You can set the table back to updatable by running:
ALTER FOREIGN TABLE ft_facts OPTIONS ( SET updatable 'true' );
The updatable property at the table level overrides the foreign server setting.
In addition to changing OPTIONS , you can also add and drop columns with the ALTER
FOREIGN TABLE statement. The statement is covered in PostgreSQL Manual ALTER
FOREIGN TABLE .
Querying Nonconventional Data Sources
The database world does not appear to be getting more homogeneous. Exotic databases
are sprouting up faster than we can keep tabs on. Some are fads and quickly drown in
their own hype. Some aspire to dethrone relational databases altogether. Some could
hardly be considered databases. The introduction of FDWs is in part a response to the
growing diversity. FDW assimilates without compromising the PosgreSQL core.
In this next example, we'll demonstrate how to use the www_fdw FDW to query web
services. We borrowed the example from www_fdw Examples .
The www_fdw FDW is not generally packaged with PostgreSQL. If you are on Linux/
Unix, it's an easy compile if you have the postgresql-dev package installed and can
download the latest source . We did the work of compiling for some Windows platforms;
you can download our binaries from Windows-32 9.1 FDWs and Windows-64 9.3
FDWs .
Now create an extension to hold the FDW:
CREATE EXTENSION www_fdw ;
Then create your Google foreign data server:
CREATE SERVER www_fdw_server_google_search
FOREIGN DATA WRAPPER www_fdw
OPTIONS ( uri 'http://ajax.googleapis.com/ajax/services/search/web?v=1.0' );
The default format supported by www_fdw is JSON, so we didn't need to include it in the
OPTIONS modifier. The other supported format is XML. For details on additional pa‐
rameters that you can set, refer to the www_fdw documentation . Each FDW is different
and comes with its own API settings.
Search WWH ::




Custom Search