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Document lack of validation when attaching foreign partitions. 

Ashutosh Bapat, revised a bit by me.

Discussion: http://postgr.es/m/CAFjFpRdLaCa-1wJase0=YWG5o3cJnbuUt_vrqm2TDBKM_vQ_oA@mail.gmail.com
This commit is contained in:
Robert Haas 2017-03-09 13:09:48 -05:00
parent 054637d2e0
commit b54aad8e34
1 changed files with 19 additions and 12 deletions
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31
doc/src/sgml/ref/alter_table.sgml
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@ -743,18 +743,25 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable>
</para> </para>
<para> <para>
A full table scan is performed on the table being attached to check that If the new partition is a regular table, a full table scan is performed
no existing row in the table violates the partition constraint. It is to check that no existing row in the table violates the partition
possible to avoid this scan by adding a valid <literal>CHECK</literal> constraint. It is possible to avoid this scan by adding a valid
constraint to the table that would allow only the rows satisfying the <literal>CHECK</literal> constraint to the table that would allow only
desired partition constraint before running this command. It will be the rows satisfying the desired partition constraint before running this
determined using such a constraint that the table need not be scanned command. It will be determined using such a constraint that the table
to validate the partition constraint. This does not work, however, if need not be scanned to validate the partition constraint. This does not
any of the partition keys is an expression and the partition does not work, however, if any of the partition keys is an expression and the
accept <literal>NULL</literal> values. If attaching a list partition partition does not accept <literal>NULL</literal> values. If attaching
that will not accept <literal>NULL</literal> values, also add a list partition that will not accept <literal>NULL</literal> values,
<literal>NOT NULL</literal> constraint to the partition key column, also add <literal>NOT NULL</literal> constraint to the partition key
unless it's an expression. column, unless it's an expression.
</para>
<para>
If the new partition is a foreign table, nothing is done to verify
that all the rows in the foreign table obey the partition constraint.
(See the discussion in <xref linkend="SQL-CREATEFOREIGNTABLE"> about
constraints on the foreign table.)
</para> </para>
</listitem> </listitem>
</varlistentry> </varlistentry>