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Abuhujair Javed
Postgres FD Implementation
Commits
c6aeba35
Commit
c6aeba35
authored
Jan 03, 2016
by
Tom Lane
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Do some copy-editing on the docs for replication origins.
Minor grammar and markup improvements.
parent
02798919
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46 additions
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40 deletions
+46
-40
doc/src/sgml/func.sgml
doc/src/sgml/func.sgml
+21
-18
doc/src/sgml/replication-origins.sgml
doc/src/sgml/replication-origins.sgml
+25
-22
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doc/src/sgml/func.sgml
View file @
c6aeba35
...
...
@@ -17228,7 +17228,8 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
in
<xref
linkend=
"functions-replication-table"
>
are for
controlling and interacting with replication features.
See
<xref
linkend=
"streaming-replication"
>
,
<xref
linkend=
"streaming-replication-slots"
>
,
<xref
linkend=
"replication-origins"
>
<xref
linkend=
"streaming-replication-slots"
>
, and
<xref
linkend=
"replication-origins"
>
for information about the underlying features. Use of these
functions is restricted to superusers.
</para>
...
...
@@ -17239,9 +17240,11 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
</para>
<para>
The functions described in
<xref
linkend=
"functions-snapshot-synchronization"
>
,
<xref
linkend=
"functions-recovery-control"
>
, and
<xref
linkend=
"functions-admin-backup"
>
are also relevant for replication.
The functions described in
<xref
linkend=
"functions-admin-backup"
>
,
<xref
linkend=
"functions-recovery-control"
>
, and
<xref
linkend=
"functions-snapshot-synchronization"
>
are also relevant for replication.
</para>
<table
id=
"functions-replication-table"
>
...
...
@@ -17401,11 +17404,11 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
<literal><function>
pg_replication_origin_create(
<parameter>
node_name
</parameter>
<type>
text
</type>
)
</function></literal>
</entry>
<entry>
<
parameter>
internal_id
</parameter>
<
type>
oid
</type>
<type>
oid
</type>
</entry>
<entry>
Create a replication origin with the
passed i
n external
name, and
create an internal id for
it.
Create a replication origin with the
give
n external
name, and
return the internal id assigned to
it.
</entry>
</row>
...
...
@@ -17420,7 +17423,7 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
void
</entry>
<entry>
Delete a previously created replication origin, including
the
Delete a previously created replication origin, including
any
associated replay progress.
</entry>
</row>
...
...
@@ -17433,10 +17436,10 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
<literal><function>
pg_replication_origin_oid(
<parameter>
node_name
</parameter>
<type>
text
</type>
)
</function></literal>
</entry>
<entry>
<
parameter>
internal_id
</parameter>
<
type>
oid
</type>
<type>
oid
</type>
</entry>
<entry>
Lookup replication origin by name and return the internal id. If no
Lookup
a
replication origin by name and return the internal id. If no
corresponding replication origin is found an error is thrown.
</entry>
</row>
...
...
@@ -17452,7 +17455,7 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
void
</entry>
<entry>
Configure the current session to be replaying from the passed i
n
Mark the current session as replaying from the give
n
origin, allowing replay progress to be tracked. Use
<function>
pg_replication_origin_session_reset
</function>
to revert.
Can only be used if no previous origin is configured.
...
...
@@ -17483,7 +17486,7 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
<literal><function>
pg_replication_origin_session_is_setup()
</function></literal>
</entry>
<entry>
bool
<type>
bool
</type>
</entry>
<entry>
Has a replication origin been configured in the current session?
...
...
@@ -17498,7 +17501,7 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
<literal><function>
pg_replication_origin_session_progress(
<parameter>
flush
</parameter>
<type>
bool
</type>
)
</function></literal>
</entry>
<entry>
pg_lsn
<type>
pg_lsn
</type>
</entry>
<entry>
Return the replay position for the replication origin configured in
...
...
@@ -17519,8 +17522,8 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
void
</entry>
<entry>
Mark the current transaction
to be
replaying a transaction that has
committed at the
passed i
n
<acronym>
LSN
</acronym>
and timestamp. Can
Mark the current transaction
as
replaying a transaction that has
committed at the
give
n
<acronym>
LSN
</acronym>
and timestamp. Can
only be called when a replication origin has previously been
configured using
<function>
pg_replication_origin_session_setup()
</function>
.
...
...
@@ -17554,7 +17557,7 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
void
</entry>
<entry>
Set replication progress for the
passed in node to the passed i
n
Set replication progress for the
given node to the give
n
position. This primarily is useful for setting up the initial position
or a new position after configuration changes and similar. Be aware
that careless use of this function can lead to inconsistently
...
...
@@ -17570,10 +17573,10 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
<literal><function>
pg_replication_origin_progress(
<parameter>
node_name
</parameter>
<type>
text
</type>
,
<parameter>
flush
</parameter>
<type>
bool
</type>
)
</function></literal>
</entry>
<entry>
pg_lsn
<type>
pg_lsn
</type>
</entry>
<entry>
Return the replay position for the
passed i
n replication origin. The
Return the replay position for the
give
n replication origin. The
parameter
<parameter>
flush
</parameter>
determines whether the
corresponding local transaction will be guaranteed to have been
flushed to disk or not.
...
...
doc/src/sgml/replication-origins.sgml
View file @
c6aeba35
<!-- doc/src/sgml/replication-origins.sgml -->
<chapter id="replication-origins">
<title>Replication Progress Tracking</title>
<indexterm zone="replication-origins">
<primary>Replication Progress Tracking</primary>
</indexterm>
...
...
@@ -11,46 +12,48 @@
<para>
Replication origins are intended to make it easier to implement
logical replication solutions on top
of <
xref linkend="logicaldecoding">. They provide a solution to two
common problems:
of <
link linkend="logicaldecoding">logical decoding</link>.
They provide a solution to two
common problems:
<itemizedlist>
<listitem><para>How to safely keep track of replication progress</para></listitem>
<listitem><para>How to change replication behavior, based on the
origin of a row; e.g. to avoid loops in bi-directional replication
setups</para></listitem>
<listitem>
<para>How to safely keep track of replication progress</para>
</listitem>
<listitem>
<para>How to change replication behavior based on the
origin of a row; for example, to prevent loops in bi-directional
replication setups</para>
</listitem>
</itemizedlist>
</para>
<para>
Replication origins
consist out of a name and an <type>oid</type>
. The name,
Replication origins
have just two properties, a name and an OID
. The name,
which is what should be used to refer to the origin across systems, is
free-form <type>text</type>. It should be used in a way that makes conflicts
between replication origins created by different replication solutions
unlikely; e.g. by prefixing the replication solution's name to it.
The
<type>oid</type>
is used only to avoid having to store the long version
The
OID
is used only to avoid having to store the long version
in situations where space efficiency is important. It should never be shared
between
systems.
across
systems.
</para>
<para>
Replication origins can be created using the
Replication origins can be created using the
function
<link linkend="pg-replication-origin-create"><function>pg_replication_origin_create()</function></link>;
dropped using
<link linkend="pg-replication-origin-drop"><function>pg_replication_origin_drop()</function></link>;
and seen in the
<link linkend="catalog-pg-replication-origin"><structname>pg_replication_origin</structname></link>
catalog.
system
catalog.
</para>
<para>
When replicating from one system to another (independent of the fact that
those two might be in the same cluster, or even same database) one
nontrivial part of building a replication solution is to keep track of
One nontrivial part of building a replication solution is to keep track of
replay progress in a safe manner. When the applying process, or the whole
cluster, dies, it needs to be possible to find out up to where data has
successfully been replicated. Naive solutions to this
like updating a row in
a table for every replayed transaction have problems like run-time overhead
bloat.
successfully been replicated. Naive solutions to this
, such as updating a
row in a table for every replayed transaction, have problems like run-time
overhead and database
bloat.
</para>
<para>
...
...
@@ -74,20 +77,20 @@
</para>
<para>
In
more complex replication topologies
than replication from exactly one
system to one other, another problem can be that it is hard to avoid
In
replication topologies more complex
than replication from exactly one
system to one other
system
, another problem can be that it is hard to avoid
replicating replayed rows again. That can lead both to cycles in the
replication and inefficiencies. Replication origins provide an optional
mechanism to recognize and prevent that. When configured using the functions
referenced in the previous paragraph, every change and transaction passed to
output plugin callbacks (see <xref linkend="logicaldecoding-output-plugin">)
generated by the session is tagged with the replication origin of the
generating session. This allows t
o treat
them differently in the output
plugin, e.g. ignoring all but locally
originating rows. Additionally
generating session. This allows t
reating
them differently in the output
plugin, e.g. ignoring all but locally
-
originating rows. Additionally
the <link linkend="logicaldecoding-output-plugin-filter-origin">
<function>filter_by_origin_cb</function></link> callback can be used
to filter the logical decoding change stream based on the
source. While less flexible, filtering via that callback is
considerably more efficient.
considerably more efficient
than doing it in the output plugin
.
</para>
</chapter>
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