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Add a xid argument to the filter_prepare callback for output plugins.

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Along with gid, this provides a different way to identify the transaction.
The users that use xid in some way to prepare the transactions can use it
to filter prepare transactions. The later commands COMMIT PREPARED or
ROLLBACK PREPARED carries both identifiers, providing an output plugin the
choice of what to use.

Author: Markus Wanner
Reviewed-by: Vignesh C, Amit Kapila
Discussion: https://postgr.es/m/ee280000-7355-c4dc-e47b-2436e7be959c@enterprisedb.com
This commit is contained in:
Amit Kapila
2021-03-30 10:34:43 +05:30
parent bc2797ebb1
commit f64ea6dc5c
6 changed files with 38 additions and 21 deletions
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29
doc/src/sgml/logicaldecoding.sgml
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@ -794,20 +794,25 @@ typedef void (*LogicalDecodeMessageCB) (struct LogicalDecodingContext *ctx,
<command>COMMIT PREPARED</command> time. To signal that
decoding should be skipped, return <literal>true</literal>;
<literal>false</literal> otherwise. When the callback is not
defined, <literal>false</literal> is assumed (i.e. nothing is
filtered).
defined, <literal>false</literal> is assumed (i.e. no filtering, all
transactions using two-phase commit are decoded in two phases as well).
<programlisting>
typedef bool (*LogicalDecodeFilterPrepareCB) (struct LogicalDecodingContext *ctx,
TransactionId xid,
const char *gid);
</programlisting>
The <parameter>ctx</parameter> parameter has the same contents as for the
other callbacks. The <parameter>gid</parameter> is the identifier that later
identifies this transaction for <command>COMMIT PREPARED</command> or
<command>ROLLBACK PREPARED</command>.
The <parameter>ctx</parameter> parameter has the same contents as for
the other callbacks. The parameters <parameter>xid</parameter>
and <parameter>gid</parameter> provide two different ways to identify
the transaction. The later <command>COMMIT PREPARED</command> or
<command>ROLLBACK PREPARED</command> carries both identifiers,
providing an output plugin the choice of what to use.
</para>
<para>
The callback has to provide the same static answer for a given
<parameter>gid</parameter> every time it is called.
The callback may be invoked multiple times per transaction to decode
and must provide the same static answer for a given pair of
<parameter>xid</parameter> and <parameter>gid</parameter> every time
it is called.
</para>
</sect3>
@ -1219,9 +1224,11 @@ stream_commit_cb(...); &lt;-- commit of the streamed transaction
</para>
<para>
Optionally the output plugin can specify a name pattern in the
<function>filter_prepare_cb</function> and transactions with gid containing
that name pattern will not be decoded as a two-phase commit transaction.
Optionally the output plugin can define filtering rules via
<function>filter_prepare_cb</function> to decode only specific transaction
in two phases. This can be achieved by pattern matching on the
<parameter>gid</parameter> or via lookups using the
<parameter>xid</parameter>.
</para>
<para>