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In documentaiton, clarify which commands have reduced WAL volume for
wal_level = minimum. Backpatch to 9.1 and 9.0.
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doc/src/sgml/config.sgml

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@@ -1420,11 +1420,18 @@ SET ENABLE_SEQSCAN TO OFF;
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This parameter can only be set at server start.
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</para>
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<para>
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In <literal>minimal</> level, WAL-logging of some bulk operations, like
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<command>CREATE INDEX</>, <command>CLUSTER</> and <command>COPY</> on
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a table that was created or truncated in the same transaction can be
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safely skipped, which can make those operations much faster (see
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<xref linkend="populate-pitr">). But minimal WAL does not contain
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In <literal>minimal</> level, WAL-logging of some bulk
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operations can be safely skipped, which can make those
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operations much faster (see <xref linkend="populate-pitr">).
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Operations in which this optimization can be applied include:
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<simplelist>
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<item>CREATE TABLE AS</item>
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<item>CREATE INDEX</item>
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<item>CLUSTER</item>
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<item>COPY into tables that were created or truncated in the same
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transaction
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</simplelist>
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But minimal WAL does not contain
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enough information to reconstruct the data from a base backup and the
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WAL logs, so either <literal>archive</> or <literal>hot_standby</>
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level must be used to enable

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