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Allow bidirectional copy messages in streaming replication mode.

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Fujii Masao.  Review by Alvaro Herrera, Tom Lane, and myself.
This commit is contained in:
Robert Haas
2010-12-11 09:27:37 -05:00
parent 20f3964291
commit d3d414696f
11 changed files with 172 additions and 21 deletions
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10
doc/src/sgml/libpq.sgml
View File

@ -2194,6 +2194,16 @@ ExecStatusType PQresultStatus(const PGresult *res);
</listitem>
</varlistentry>
<varlistentry id="libpq-pgres-copy-both">
<term><literal>PGRES_COPY_BOTH</literal></term>
<listitem>
<para>
Copy In/Out (to and from server) data transfer started. This is
currently used only for streaming replication.
</para>
</listitem>
</varlistentry>
<varlistentry id="libpq-pgres-bad-response">
<term><literal>PGRES_BAD_RESPONSE</literal></term>
<listitem>

98
doc/src/sgml/protocol.sgml
View File

@ -1033,12 +1033,25 @@
</para>
<para>
The CopyInResponse and CopyOutResponse messages include fields that
inform the frontend of the number of columns per row and the format
codes being used for each column. (As of the present implementation,
all columns in a given <command>COPY</> operation will use the same
format, but the message design does not assume this.)
There is another Copy-related mode called Copy-both, which allows
high-speed bulk data transfer to <emphasis>and</> from the server.
Copy-both mode is initiated when a backend in walsender mode
executes a <command>START_REPLICATION</command> statement. The
backend sends a CopyBothResponse message to the frontend. Both
the backend and the frontend may then send CopyData messages
until the connection is terminated. See see <xref
linkend="protocol-replication">.
</para>
<para>
The CopyInResponse, CopyOutResponse and CopyBothResponse messages
include fields that inform the frontend of the number of columns
per row and the format codes being used for each column. (As of
the present implementation, all columns in a given <command>COPY</>
operation will use the same format, but the message design does not
assume this.)
</para>
</sect2>
<sect2 id="protocol-async">
@ -1344,7 +1357,7 @@ The commands accepted in walsender mode are:
WAL position <replaceable>XXX</>/<replaceable>XXX</>.
The server can reply with an error, e.g. if the requested section of WAL
has already been recycled. On success, server responds with a
CopyOutResponse message, and then starts to stream WAL to the frontend.
CopyBothResponse message, and then starts to stream WAL to the frontend.
WAL will continue to be streamed until the connection is broken;
no further commands will be accepted.
</para>
@ -2694,6 +2707,79 @@ CopyOutResponse (B)
</varlistentry>
<varlistentry>
<term>
CopyBothResponse (B)
</term>
<listitem>
<para>
<variablelist>
<varlistentry>
<term>
Byte1('W')
</term>
<listitem>
<para>
Identifies the message as a Start Copy Both response.
This message is used only for Streaming Replication.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
Int32
</term>
<listitem>
<para>
Length of message contents in bytes, including self.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
Int8
</term>
<listitem>
<para>
0 indicates the overall <command>COPY</command> format
is textual (rows separated by newlines, columns
separated by separator characters, etc). 1 indicates
the overall copy format is binary (similar to DataRow
format). See <xref linkend="sql-copy"> for more information.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
Int16
</term>
<listitem>
<para>
The number of columns in the data to be copied
(denoted <replaceable>N</> below).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
Int16[<replaceable>N</>]
</term>
<listitem>
<para>
The format codes to be used for each column.
Each must presently be zero (text) or one (binary).
All must be zero if the overall copy format is textual.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
DataRow (B)