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Improve CREATE TABLE documentation of partitioning 

Amit Langote, with corrections by me
This commit is contained in:
Simon Riggs 2017-02-10 08:59:37 +00:00
parent 62e8b38751
commit c1369fe2ea
1 changed files with 98 additions and 9 deletions
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107
doc/src/sgml/ref/create_table.sgml
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@ -85,8 +85,8 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXI
<phrase>and <replaceable class="PARAMETER">partition_bound_spec</replaceable> is:</phrase>
{ IN ( <replaceable class="PARAMETER">expression</replaceable> [, ...] ) |
FROM ( { <replaceable class="PARAMETER">expression</replaceable> | UNBOUNDED } [, ...] ) TO ( { <replaceable class="PARAMETER">expression</replaceable> | UNBOUNDED } [, ...] ) }
{ IN ( { <replaceable class="PARAMETER">bound_literal</replaceable> | NULL } [, ...] ) |
FROM ( { <replaceable class="PARAMETER">bound_literal</replaceable> | UNBOUNDED } [, ...] ) TO ( { <replaceable class="PARAMETER">bound_literal</replaceable> | UNBOUNDED } [, ...] ) }
<phrase><replaceable class="PARAMETER">index_parameters</replaceable> in <literal>UNIQUE</literal>, <literal>PRIMARY KEY</literal>, and <literal>EXCLUDE</literal> constraints are:</phrase>
@ -261,10 +261,48 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXI
any existing partition of that parent.
</para>
<note>
<para>
Each of the values specified in the partition bound specification is
a literal, <literal>NULL</literal>, or <literal>UNBOUNDED</literal>.
A literal is either a numeric constant or a string constant that is
coercable to the corresponding partition key column's type.
</para>
<para>
When creating a range partition, the lower bound specified with
<literal>FROM</literal> is an inclusive bound, whereas the upper bound
specified with <literal>TO</literal> is an exclusive bound. That is,
the values specified in the <literal>FROM</literal> list are accepted
values of the corresponding partition key columns in a given partition,
whereas those in the <literal>TO</literal> list are not. To be precise,
this applies only to the first of the partition key columns for which
the corresponding values in the <literal>FROM</literal> and
<literal>TO</literal> lists are not equal. All rows in a given
partition contain the same values for all preceding columns, equal to
those specified in <literal>FROM</literal> and <literal>TO</literal>
lists. On the other hand, any subsequent columns are insignificant
as far as implicit partition constraint is concerned.
Specifying <literal>UNBOUNDED</literal> in <literal>FROM</literal>
signifies <literal>-infinity</literal> as the lower bound of the
corresponding column, whereas it signifies <literal>+infinity</literal>
as the upper bound when specified in <literal>TO</literal>.
</para>
<para>
When creating a list partition, <literal>NULL</literal> can be specified
to signify that the partition allows the partition key column to be null.
However, there cannot be more than one such list partitions for a given
parent table. <literal>NULL</literal> cannot specified for range
partitions.
</para>
</note>
<para>
A partition cannot have columns other than those inherited from the
parent. That includes the <structfield>oid</> column, which can be
specified using the <literal>WITH (OIDS)</literal> clause.
parent. If the parent is specified <literal>WITH OIDS</literal> then
the partitions must also explicitly specify <literal>WITH OIDS</literal>.
Defaults and constraints can optionally be specified for each of the
inherited columns. One can also specify table constraints in addition
to those inherited from the parent. If a check constraint with the name
@ -386,11 +424,12 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXI
<firstterm>partitioned</firstterm> table. The parenthesized list of
columns or expressions forms the <firstterm>partition key</firstterm>
for the table. When using range partitioning, the partition key can
include multiple columns or expressions, but for list partitioning, the
partition key must consist of a single column or expression. If no
btree operator class is specified when creating a partitioned table,
the default btree operator class for the datatype will be used. If
there is none, an error will be reported.
include multiple columns or expressions (up to 32, but this limit can
altered when building <productname>PostgreSQL</productname>.), but for
list partitioning, the partition key must consist of a single column or
expression. If no btree operator class is specified when creating a
partitioned table, the default btree operator class for the datatype will
be used. If there is none, an error will be reported.
</para>
<para>
@ -1482,6 +1521,16 @@ CREATE TABLE measurement (
peaktemp int,
unitsales int
) PARTITION BY RANGE (logdate);
</programlisting></para>
<para>
Create a range partitioned table with multiple columns in the partition key:
<programlisting>
CREATE TABLE measurement_year_month (
logdate date not null,
peaktemp int,
unitsales int
) PARTITION BY RANGE (EXTRACT(YEAR FROM logdate), EXTRACT(MONTH FROM logdate));
</programlisting></para>
<para>
@ -1503,6 +1552,27 @@ CREATE TABLE measurement_y2016m07
) FOR VALUES FROM ('2016-07-01') TO ('2016-08-01');
</programlisting></para>
<para>
Create a few partitions of a range partitioned table with multiple
columns in the partition key:
<programlisting>
CREATE TABLE measurement_ym_older
PARTITION OF measurement_year_month
FOR VALUES FROM (unbounded, unbounded) TO (2016, 11);
CREATE TABLE measurement_ym_y2016m11
PARTITION OF measurement_year_month
FOR VALUES FROM (2016, 11) TO (2016, 12);
CREATE TABLE measurement_ym_y2016m12
PARTITION OF measurement_year_month
FOR VALUES FROM (2016, 12) TO (2017, 01);
CREATE TABLE measurement_ym_y2017m01
PARTITION OF measurement_year_month
FOR VALUES FROM (2017, 01) TO (2017, 02);
</programlisting></para>
<para>
Create partition of a list partitioned table:
<programlisting>
@ -1705,6 +1775,25 @@ CREATE TABLE cities_ab_10000_to_100000
effect can be had using the OID feature.
</para>
</refsect2>
<refsect2>
<title><literal>PARTITION BY</> Clause</title>
<para>
The <literal>PARTITION BY</> clause is a
<productname>PostgreSQL</productname> extension.
</para>
</refsect2>
<refsect2>
<title><literal>PARTITION OF</> Clause</title>
<para>
The <literal>PARTITION OF</> clause is a
<productname>PostgreSQL</productname> extension.
</para>
</refsect2>
</refsect1>