ON MASTER support for s3 and custom protocols
@@ -360,9 +360,15 @@ CREATE WRITABLE EXTERNAL WEB TABLE <varname>table_name</varname>
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<pt>ON MASTER</pt>
- <pd>Permitted only on readable and writable external tables created with the
- <codeph>s3</codeph> protocol. Restricts all table-related
- operations to the Greenplum master segment.</pd>
+ <pd>Restricts all table-related operations to the Greenplum master segment. Permitted
+ only on readable and writable external tables created with the
+ <codeph>s3</codeph> or custom protocols. The <codeph>gpfdist</codeph>,
+ <codeph>gpfdists</codeph>, <codeph>gphdfs</codeph>, and <codeph>file</codeph>
+ protocols do not support <codeph>ON MASTER</codeph>.
+ <note>Be aware of potential resource impacts when reading from or writing to
+ external tables you create with the <codeph>ON MASTER</codeph> clause. You may
+ encounter performance issues when you restrict table operations solely to the
+ Greenplum master segment.</note></pd>
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<plentry>
<pt>EXECUTE <varname>'command'</varname> [ON ...]</pt>
