DOCS: External table - gpfdist or file protocol w/named pipe data source allows only 1 reader. From 4.3.x
@@ -192,8 +192,8 @@ CREATE WRITABLE EXTERNAL WEB TABLE <varname>table_name</varname>
input stream of data. External web tables are not rescannable during query
execution.</pd>
<pd>The <codeph>s3</codeph> protocol does not support external web tables. You can,
- however, create an external web table that executes a third-party tool to read data
- from or write data to S3 directly.</pd>
+ however, create an external web table that executes a third-party tool to read data from
+ or write data to S3 directly.</pd>
</plentry>
<plentry>
<pt>
@@ -360,14 +360,13 @@ CREATE WRITABLE EXTERNAL WEB TABLE <varname>table_name</varname>
</plentry>
<plentry>
<pt>ON MASTER</pt>
- <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
+ <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>
</plentry>
<plentry>
@@ -656,6 +655,11 @@ customer_id=123;</codeblock>
database owner privilege is required. If <codeph>*.*</codeph> is specified, operating
system super-user privilege is required.</p></li>
</ul>
+ <p>When multiple Greenplum Database external tables are defined with the
+ <codeph>gpfdist</codeph>, <codeph>gpfdists</codeph>, or <codeph>file</codeph> protocol and
+ access the same named pipe a Linux system, Greenplum Database restricts access to the named
+ pipe to a single reader. An error is returned if a second reader attempts to access the
+ named pipe. </p>
</section>
<section id="section9"><title>HDFS File Format Support for the gphdfs Protocol</title><p>If you
specify <codeph>gphdfs</codeph> protocol to read or write file to a Hadoop file system
