database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-28 23:42:10 +03:00
Code Activity

Add a message type header to the CopyData messages sent from primary

Browse Source 
to standby in streaming replication. While we only have one message type
at the moment, adding a message type header makes this easier to extend.
This commit is contained in:
Heikki Linnakangas
2010-02-03 09:47:19 +00:00
parent 47c5b8f558
commit 808969d0e7
5 changed files with 117 additions and 35 deletions
Download Patch File Download Diff File Expand all files Collapse all files

61
doc/src/sgml/protocol.sgml
View File

@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/protocol.sgml,v 1.77 2010/01/15 09:18:59 heikki Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/protocol.sgml,v 1.78 2010/02/03 09:47:19 heikki Exp $ -->
<chapter id="protocol">
<title>Frontend/Backend Protocol</title>
@ -4179,12 +4179,65 @@ The commands accepted in walsender mode are:
already been recycled. On success, server responds with a
CopyOutResponse message, and backend starts to stream WAL as CopyData
messages.
The payload in CopyData message consists of the following format.
</para>
<para>
The payload in each CopyData message consists of an XLogRecPtr,
indicating the starting point of the WAL in the message, immediately
followed by the WAL data itself.
<variablelist>
<varlistentry>
<term>
XLogData (B)
</term>
<listitem>
<para>
<variablelist>
<varlistentry>
<term>
Byte1('w')
</term>
<listitem>
<para>
Identifies the message as WAL data.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
Int32
</term>
<listitem>
<para>
The log file number of the LSN, indicating the starting point of
the WAL in the message.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
Int32
</term>
<listitem>
<para>
The byte offset of the LSN, indicating the starting point of
the WAL in the message.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
Byte<replaceable>n</replaceable>
</term>
<listitem>
<para>
Data that forms part of WAL data stream.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
A single WAL record is never split across two CopyData messages. When