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Raise a warning if there is a possibility of data from multiple origins.

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This commit raises a warning message for a combination of options
('copy_data = true' and 'origin = none') during CREATE/ALTER subscription
operations if the publication tables were also replicated from other
publishers.

During replication, we can skip the data from other origins as we have that
information in WAL but that is not possible during initial sync so we raise
a warning if there is such a possibility.

Author: Vignesh C
Reviewed-By: Peter Smith, Amit Kapila, Jonathan Katz, Shi yu, Wang wei
Discussion: https://www.postgresql.org/message-id/CALDaNm0gwjY_4HFxvvty01BOT01q_fJLKQ3pWP9=9orqubhjcQ@mail.gmail.com
This commit is contained in:
Amit Kapila
2022-09-08 06:54:13 +05:30
parent 4b4663fb4a
commit 8756930190
4 changed files with 258 additions and 29 deletions
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5
doc/src/sgml/ref/alter_subscription.sgml
View File

@ -172,6 +172,11 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
Previously subscribed tables are not copied, even if a table's row
filter <literal>WHERE</literal> clause has since been modified.
</para>
<para>
See <xref linkend="sql-createsubscription-notes"/> for details of
how <literal>copy_data = true</literal> can interact with the
<literal>origin</literal> parameter.
</para>
</listitem>
</varlistentry>
</variablelist></para>

35
doc/src/sgml/ref/create_subscription.sgml
View File

@ -213,6 +213,11 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
will affect what data is copied. Refer to the
<xref linkend="sql-createsubscription-notes" /> for details.
</para>
<para>
See <xref linkend="sql-createsubscription-notes"/> for details of how
<literal>copy_data = true</literal> can interact with the
<literal>origin</literal> parameter.
</para>
</listitem>
</varlistentry>
@ -315,6 +320,11 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
to <literal>any</literal> means that the publisher sends changes
regardless of their origin. The default is <literal>any</literal>.
</para>
<para>
See <xref linkend="sql-createsubscription-notes"/> for details of how
<literal>copy_data = true</literal> can interact with the
<literal>origin</literal> parameter.
</para>
</listitem>
</varlistentry>
</variablelist></para>
@ -386,6 +396,31 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
can have non-existent publications.
</para>
<para>
When using a subscription parameter combination of
<literal>copy_data = true</literal> and <literal>origin = NONE</literal>,
the initial sync table data is copied directly from the publisher, meaning
that knowledge of the true origin of that data is not possible. If the
publisher also has subscriptions then the copied table data might have
originated from further upstream. This scenario is detected and a WARNING is
logged to the user, but the warning is only an indication of a potential
problem; it is the user's responsibility to make the necessary checks to
ensure the copied data origins are really as wanted or not.
</para>
<para>
To find which tables might potentially include non-local origins (due to
other subscriptions created on the publisher) try this SQL query:
<programlisting>
# substitute &lt;pub-names&gt; below with your publication name(s) to be queried
SELECT DISTINCT N.nspname AS schemaname, C.relname AS tablename
FROM pg_publication P,
LATERAL pg_get_publication_tables(P.pubname) GPT
JOIN pg_subscription_rel PS ON (GPT.relid = PS.srrelid),
pg_class C JOIN pg_namespace N ON (N.oid = C.relnamespace)
WHERE C.oid = GPT.relid AND P.pubname IN (&lt;pub-names&gt;);
</programlisting></para>
</refsect1>
<refsect1>