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Allow UNIQUE indexes on partitioned tables

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If we restrict unique constraints on partitioned tables so that they
must always include the partition key, then our standard approach to
unique indexes already works --- each unique key is forced to exist
within a single partition, so enforcing the unique restriction in each
index individually is enough to have it enforced globally.  Therefore we
can implement unique indexes on partitions by simply removing a few
restrictions (and adding others.)

Discussion: https://postgr.es/m/20171222212921.hi6hg6pem2w2t36z@alvherre.pgsql
Discussion: https://postgr.es/m/20171229230607.3iib6b62fn3uaf47@alvherre.pgsql
Reviewed-by: Simon Riggs, Jesper Pedersen, Peter Eisentraut, Jaime
	Casanova, Amit Langote
This commit is contained in:
Alvaro Herrera
2018-02-19 16:59:37 -03:00
parent 524d64ea8e
commit eb7ed3f306
27 changed files with 907 additions and 95 deletions
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18
doc/src/sgml/ref/create_table.sgml
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@@ -546,8 +546,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
</para>
<para>
Partitioned tables do not support <literal>UNIQUE</literal>,
<literal>PRIMARY KEY</literal>, <literal>EXCLUDE</literal>, or
Partitioned tables do not support <literal>EXCLUDE</literal> or
<literal>FOREIGN KEY</literal> constraints; however, you can define
these constraints on individual partitions.
</para>
@@ -786,6 +785,14 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
primary key constraint defined for the table. (Otherwise it
would just be the same constraint listed twice.)
</para>
<para>
When used on partitioned tables, unique constraints must include all the
columns of the partition key.
If any partitions are in turn partitioned, all columns of each partition
key are considered at each level below the <literal>UNIQUE</literal>
constraint.
</para>
</listitem>
</varlistentry>
@@ -814,6 +821,13 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
about the design of the schema, since a primary key implies that other
tables can rely on this set of columns as a unique identifier for rows.
</para>
<para>
<literal>PRIMARY KEY</literal> constraints share the restrictions that
<literal>UNIQUE</literal> constraints have when placed on partitioned
tables.
</para>
</listitem>
</varlistentry>