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[CF 3659] v38 - Add SPLIT PARTITION/MERGE PARTITIONS commands
This branch was automatically generated by a robot using patches from an email thread registered at: https://commitfest.postgresql.org/patch/3659 The branch will be overwritten each time a new patch version is posted to the thread, and also periodically to check for bitrot caused by changes on the master branch. Patch(es): https://www.postgresql.org/message-id/[email protected] Author(s): Dmitry Koval
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‎doc/src/sgml/ddl.sgml‎

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@@ -4441,6 +4441,44 @@ ALTER INDEX measurement_city_id_logdate_key
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...
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</programlisting>
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</para>
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<para>
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There is also an option for merging multiple table partitions into
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a single partition using the
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<link linkend="sql-altertable-merge-partitions"><command>ALTER TABLE ... MERGE PARTITIONS</command></link>.
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This feature simplifies the management of partitioned tables by allowing
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users to combine partitions that are no longer needed as
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separate entities. It's important to note that this operation is not
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supported for hash-partitioned tables and acquires an
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<literal>ACCESS EXCLUSIVE</literal> lock, which could impact high-load
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systems due to the lock's restrictive nature. For example, we can
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merge three monthly partitions into one quarter partition:
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<programlisting>
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ALTER TABLE measurement
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MERGE PARTITIONS (measurement_y2006m01,
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measurement_y2006m02,
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measurement_y2006m03) INTO measurement_y2006q1;
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</programlisting>
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</para>
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<para>
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Similarly to merging multiple table partitions, there is an option for
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splitting a single partition into multiple using the
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<link linkend="sql-altertable-split-partition"><command>ALTER TABLE ... SPLIT PARTITION</command></link>.
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This feature could come in handy when one partition grows too big
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and needs to be split into multiple. It's important to note that
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this operation is not supported for hash-partitioned tables and acquires
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an <literal>ACCESS EXCLUSIVE</literal> lock, which could impact high-load
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systems due to the lock's restrictive nature. For example, we can split
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the quarter partition back to monthly partitions:
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<programlisting>
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ALTER TABLE measurement SPLIT PARTITION measurement_y2006q1 INTO
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(PARTITION measurement_y2006m01 FOR VALUES FROM ('2006-01-01') TO ('2006-02-01'),
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PARTITION measurement_y2006m02 FOR VALUES FROM ('2006-02-01') TO ('2006-03-01'),
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PARTITION measurement_y2006m03 FOR VALUES FROM ('2006-03-01') TO ('2006-04-01'));
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</programlisting>
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</para>
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</sect3>
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<sect3 id="ddl-partitioning-declarative-limitations">

‎doc/src/sgml/ref/alter_table.sgml‎

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@@ -37,6 +37,13 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
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ATTACH PARTITION <replaceable class="parameter">partition_name</replaceable> { FOR VALUES <replaceable class="parameter">partition_bound_spec</replaceable> | DEFAULT }
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ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
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DETACH PARTITION <replaceable class="parameter">partition_name</replaceable> [ CONCURRENTLY | FINALIZE ]
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ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
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SPLIT PARTITION <replaceable class="parameter">partition_name</replaceable> INTO
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(PARTITION <replaceable class="parameter">partition_name1</replaceable> { FOR VALUES <replaceable class="parameter">partition_bound_spec</replaceable> | DEFAULT },
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PARTITION <replaceable class="parameter">partition_name2</replaceable> { FOR VALUES <replaceable class="parameter">partition_bound_spec</replaceable> | DEFAULT } [, ...])
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ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
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MERGE PARTITIONS (<replaceable class="parameter">partition_name1</replaceable>, <replaceable class="parameter">partition_name2</replaceable> [, ...])
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INTO <replaceable class="parameter">partition_name</replaceable>
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<phrase>where <replaceable class="parameter">action</replaceable> is one of:</phrase>
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@@ -1147,14 +1154,142 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
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</listitem>
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</varlistentry>
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<varlistentry id="sql-altertable-split-partition">
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<term><literal>SPLIT PARTITION <replaceable class="parameter">partition_name</replaceable> INTO (PARTITION <replaceable class="parameter">partition_name1</replaceable> { FOR VALUES <replaceable class="parameter">partition_bound_spec</replaceable> | DEFAULT }, PARTITION <replaceable class="parameter">partition_name2</replaceable> { FOR VALUES <replaceable class="parameter">partition_bound_spec</replaceable> | DEFAULT } [, ...])</literal></term>
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<listitem>
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<para>
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This form splits a single partition of the target table. Hash-partitioning
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is not supported. Bounds of new partitions should not overlap with new and
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existing partitions (except <replaceable class="parameter">partition_name</replaceable>).
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If the split partition is a DEFAULT partition, one of the new partitions must be DEFAULT.
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In case one of the new partitions or one of existing partitions is DEFAULT,
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new partitions <replaceable class="parameter">partition_name1</replaceable>,
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<replaceable class="parameter">partition_name2</replaceable>, ... can have spaces
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between partitions bounds. If the partitioned table does not have a DEFAULT
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partition, the DEFAULT partition can be defined as one of the new partitions.
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</para>
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<para>
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In case new partitions do not contain a DEFAULT partition and the partitioned table
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does not have a DEFAULT partition, the following must be true: sum bounds of
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new partitions <replaceable class="parameter">partition_name1</replaceable>,
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<replaceable class="parameter">partition_name2</replaceable>, ... should be
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equal to bound of split partition <replaceable class="parameter">partition_name</replaceable>.
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One of the new partitions <replaceable class="parameter">partition_name1</replaceable>,
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<replaceable class="parameter">partition_name2</replaceable>, ... can have
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the same name as split partition <replaceable class="parameter">partition_name</replaceable>
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(this is suitable in case of splitting a DEFAULT partition: we split it, but after
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splitting we have a partition with the same name).
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Only simple, non-partitioned partition can be split.
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</para>
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<para>
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New partitions will have the same owner as the parent.
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</para>
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<para>
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The indexes and identity are created later, after moving the data
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into the new partitions.
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Extended statistics aren't copied from the parent table, for consistency with
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<command>CREATE TABLE PARTITION OF</command>.
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New partitions will have the same table access method as the parent.
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If the parent table is persistent then new partitions are created
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persistent. If the parent table is temporary then new partitions
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are also created temporary. New partitions will also be created in
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the same tablespace as the parent.
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</para>
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<note>
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<para>
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This command acquires an <literal>ACCESS EXCLUSIVE</literal> lock.
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This is a significant limitation, which limits the usage of this
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command with large partitioned tables under a high load.
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</para>
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</note>
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</listitem>
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</varlistentry>
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<varlistentry id="sql-altertable-merge-partitions">
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<term><literal>MERGE PARTITIONS (<replaceable class="parameter">partition_name1</replaceable>, <replaceable class="parameter">partition_name2</replaceable> [, ...]) INTO <replaceable class="parameter">partition_name</replaceable></literal></term>
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<listitem>
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<para>
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This form merges several partitions into the one partition of the target table.
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Hash-partitioning is not supported. If DEFAULT partition is not in the
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list of partitions <replaceable class="parameter">partition_name1</replaceable>,
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<replaceable class="parameter">partition_name2</replaceable> [, ...]:
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<itemizedlist>
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<listitem>
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<para>
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For range-partitioned tables it is necessary that the ranges
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of the partitions <replaceable class="parameter">partition_name1</replaceable>,
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<replaceable class="parameter">partition_name2</replaceable> [, ...] can
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be merged into one range without spaces and overlaps (otherwise an error
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will be generated). The combined range will be the range for the partition
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<replaceable class="parameter">partition_name</replaceable>.
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</para>
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</listitem>
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<listitem>
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<para>
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For list-partitioned tables the value lists of all partitions
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<replaceable class="parameter">partition_name1</replaceable>,
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<replaceable class="parameter">partition_name2</replaceable> [, ...] are
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combined and form the list of values of partition
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<replaceable class="parameter">partition_name</replaceable>.
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</para>
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</listitem>
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</itemizedlist>
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If DEFAULT partition is in the list of partitions <replaceable class="parameter">partition_name1</replaceable>,
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<replaceable class="parameter">partition_name2</replaceable> [, ...]:
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<itemizedlist>
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<listitem>
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<para>
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The partition <replaceable class="parameter">partition_name</replaceable>
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will be the DEFAULT partition.
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</para>
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</listitem>
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<listitem>
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<para>
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For range- and list-partitioned tables the ranges and lists of values
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of the merged partitions can be any.
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</para>
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</listitem>
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</itemizedlist>
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The new partition <replaceable class="parameter">partition_name</replaceable>
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can have the same name as one of the merged partitions. Only simple,
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non-partitioned partitions can be merged.
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</para>
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<para>
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If merged partitions have different owners, an error will be generated.
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</para>
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<para>
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The indexes and identity are created later, after moving the data
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into the new partition.
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Extended statistics aren't copied from the parent table, for consistency with
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<command>CREATE TABLE PARTITION OF</command>.
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The new partition will have the same table access method as the parent.
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If the parent table is persistent then the new partition is created
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persistent. If the parent table is temporary then the new partition
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is also created temporary. The new partition will also be created in
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the same tablespace as the parent.
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</para>
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<note>
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<para>
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This command acquires an <literal>ACCESS EXCLUSIVE</literal> lock.
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This is a significant limitation, which limits the usage of this
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command with large partitioned tables under a high load.
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</para>
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</note>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>
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All the forms of <command>ALTER TABLE</command> that act on a single table,
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except <literal>RENAME</literal>, <literal>SET SCHEMA</literal>,
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<literal>ATTACH PARTITION</literal>, and
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<literal>DETACH PARTITION</literal> can be combined into
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<literal>ATTACH PARTITION</literal>, <literal>DETACH PARTITION</literal>,
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<literal>SPLIT PARTITION</literal>, and <literal>MERGE PARTITIONS</literal>
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can be combined into
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a list of multiple alterations to be applied together. For example, it
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is possible to add several columns and/or alter the type of several
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columns in a single command. This is particularly useful with large
@@ -1397,7 +1532,8 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
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<term><replaceable class="parameter">partition_name</replaceable></term>
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<listitem>
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<para>
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The name of the table to attach as a new partition or to detach from this table.
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The name of the table to attach as a new partition or to detach from this table,
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or the name of split partition, or the name of the new merged partition.
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</para>
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</listitem>
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</varlistentry>
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DETACH PARTITION measurement_y2015m12;
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</programlisting></para>
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<para>
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To split a single partition of the range-partitioned table:
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<programlisting>
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ALTER TABLE sales_range SPLIT PARTITION sales_feb_mar_apr2023 INTO
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(PARTITION sales_feb2023 FOR VALUES FROM ('2023-02-01') TO ('2023-03-01'),
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PARTITION sales_mar2023 FOR VALUES FROM ('2023-03-01') TO ('2023-04-01'),
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PARTITION sales_apr2023 FOR VALUES FROM ('2023-04-01') TO ('2023-05-01'));
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</programlisting></para>
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<para>
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To split a single partition of the list-partitioned table:
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<programlisting>
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ALTER TABLE sales_list SPLIT PARTITION sales_all INTO
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(PARTITION sales_west FOR VALUES IN ('Lisbon', 'New York', 'Madrid'),
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PARTITION sales_east FOR VALUES IN ('Bejing', 'Delhi', 'Vladivostok'),
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PARTITION sales_central FOR VALUES IN ('Warsaw', 'Berlin', 'Kyiv'));
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</programlisting></para>
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<para>
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To merge several partitions into one partition of the target table:
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<programlisting>
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ALTER TABLE sales_list MERGE PARTITIONS (sales_west, sales_east, sales_central)
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INTO sales_all;
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</programlisting></para>
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</refsect1>
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<refsect1>

‎src/backend/catalog/heap.c‎

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@@ -105,8 +105,6 @@ static void RelationRemoveInheritance(Oid relid);
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static Oid StoreRelCheck(Relation rel, const char *ccname, Node *expr,
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bool is_enforced, bool is_validated, bool is_local,
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int16 inhcount, bool is_no_inherit, bool is_internal);
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static void StoreConstraints(Relation rel, List *cooked_constraints,
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bool is_internal);
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static bool MergeWithExistingConstraint(Relation rel, const char *ccname, Node *expr,
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bool allow_merge, bool is_local,
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bool is_enforced,
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* expressions can be added later, by direct calls to StoreAttrDefault
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* and StoreRelCheck (see AddRelationNewConstraints()).
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*/
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static void
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void
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StoreConstraints(Relation rel, List *cooked_constraints, bool is_internal)
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{
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int numchecks = 0;

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