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Doc: explain the log format of logical replication conflicts.

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This commit adds a detailed explanation of the log format for logical
replication conflicts.

Author: Hou Zhijie
Reviewed-by: Shveta Malik, Peter Smith, Hayato Kuroda
Discussion: https://postgr.es/m/OS0PR01MB5716352552DFADB8E9AD1D8994C92@OS0PR01MB5716.jpnprd01.prod.outlook.com
Discussion: https://postgr.es/m/OS0PR01MB57162EDE8BA17F3EE08A24CA948D2@OS0PR01MB5716.jpnprd01.prod.outlook.com
pull/175/head
Amit Kapila 1 year ago
parent d55322b0da
commit edcb712585
1 changed files with 105 additions and 0 deletions
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      doc/src/sgml/logical-replication.sgml

105
doc/src/sgml/logical-replication.sgml
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@ -1666,6 +1666,111 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
log.
</para>
<para>
The log format for logical replication conflicts is as follows:
<synopsis>
LOG: conflict detected on relation "<replaceable>schemaname</replaceable>.<replaceable>tablename</replaceable>": conflict=<replaceable>conflict_type</replaceable>
DETAIL: <replaceable class="parameter">detailed_explanation</replaceable>.
{<replaceable class="parameter">detail_values</replaceable> [; ... ]}.
<phrase>where <replaceable class="parameter">detail_values</replaceable> is one of:</phrase>
<literal>Key</literal> (<replaceable>column_name</replaceable> <optional>, ...</optional>)=(<replaceable>column_value</replaceable> <optional>, ...</optional>)
<literal>existing local tuple</literal> <optional>(<replaceable>column_name</replaceable> <optional>, ...</optional>)=</optional>(<replaceable>column_value</replaceable> <optional>, ...</optional>)
<literal>remote tuple</literal> <optional>(<replaceable>column_name</replaceable> <optional>, ...</optional>)=</optional>(<replaceable>column_value</replaceable> <optional>, ...</optional>)
<literal>replica identity</literal> {(<replaceable>column_name</replaceable> <optional>, ...</optional>)=(<replaceable>column_value</replaceable> <optional>, ...</optional>) | full <optional>(<replaceable>column_name</replaceable> <optional>, ...</optional>)=</optional>(<replaceable>column_value</replaceable> <optional>, ...</optional>)}
</synopsis>
The log provides the following information:
<variablelist>
<varlistentry>
<term><literal>LOG</literal></term>
<listitem>
<itemizedlist>
<listitem>
<para>
<replaceable>schemaname</replaceable>.<replaceable>tablename</replaceable>
identifies the local relation involved in the conflict.
</para>
</listitem>
<listitem>
<para>
<replaceable>conflict_type</replaceable> is the type of conflict that occurred
(e.g., <literal>insert_exists</literal>, <literal>update_exists</literal>).
</para>
</listitem>
</itemizedlist>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>DETAIL</literal></term>
<listitem>
<itemizedlist>
<listitem>
<para>
<replaceable class="parameter">detailed_explanation</replaceable> includes
the origin, transaction ID, and commit timestamp of the transaction that
modified the existing local tuple, if available.
</para>
</listitem>
<listitem>
<para>
The <literal>Key</literal> section includes the key values of the local
tuple that violated a unique constraint for
<literal>insert_exists</literal> or <literal>update_exists</literal>
conflicts.
</para>
</listitem>
<listitem>
<para>
The <literal>existing local tuple</literal> section includes the local
tuple if its origin differs from the remote tuple for
<literal>update_differ</literal> or <literal>delete_differ</literal>
conflicts, or if the key value conflicts with the remote tuple for
<literal>insert_exists</literal> or <literal>update_exists</literal>
conflicts.
</para>
</listitem>
<listitem>
<para>
The <literal>remote tuple</literal> section includes the new tuple from
the remote insert or update operation that caused the conflict. Note that
for an update operation, the column value of the new tuple will be null
if the value is unchanged and toasted.
</para>
</listitem>
<listitem>
<para>
The <literal>replica identity</literal> section includes the replica
identity key values that were used to search for the existing local
tuple to be updated or deleted. This may include the full tuple value
if the local relation is marked with
<link linkend="sql-altertable-replica-identity-full"><literal>REPLICA IDENTITY FULL</literal></link>.
</para>
</listitem>
<listitem>
<para>
<replaceable class="parameter">column_name</replaceable> is the column name.
For <literal>existing local tuple</literal>, <literal>remote tuple</literal>,
and <literal>replica identity full</literal> cases, column names are
logged only if the user lacks the privilege to access all columns of
the table. If column names are present, they appear in the same order
as the corresponding column values.
</para>
</listitem>
<listitem>
<para>
<replaceable class="parameter">column_value</replaceable> is the column value.
The large column values are truncated to 64 bytes.
</para>
</listitem>
</itemizedlist>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
Logical replication operations are performed with the privileges of the role
which owns the subscription. Permissions failures on target tables will

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