docs - updated foreign data wrapper intro.
Removed references to foreign data wrappers install with GPDB
Modified note. Added information stating PostgrSQL FDWs only access master.
<p>You can access foreign data with help from a <i>foreign-data wrapper</i>.
A foreign-data wrapper is a library that communicates with a remote
data source. This library hides the source-specific connection and data
- access details. Foreign-data wrappers provided in the Greenplum Database
- distribution, including <codeph>file_fdw</codeph> and
- <codeph>postgres_fdw</codeph>, have been modified to take advantage
- of Greenplum's parallel processing.</p>
+ access details.</p>
<note>Most PostgreSQL foreign-data wrappers should work with Greenplum
- Database. However, any foreign-data wrapper that is not provided in the
- Greenplum distribution likely connects only through the master.</note>
+ Database. However, PostgreSQL foreign-data wrappers connect only through
+ the Greenplum Database master and do not access the Greenplum Database
+ segment instances directly.</note>
<p>If none of the existing foreign-data wrappers suit your needs, you can
write your own as described in <xref href="g-devel-fdw.xml#topic1"/>.</p>
<p>To access foreign data, you create a <i>foreign server</i> object,
