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Add CREATE SEQUENCE AS <data type> clause

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This stores a data type, required to be an integer type, with the
sequence.  The sequences min and max values default to the range
supported by the type, and they cannot be set to values exceeding that
range.  The internal implementation of the sequence is not affected.

Change the serial types to create sequences of the appropriate type.
This makes sure that the min and max values of the sequence for a serial
column match the range of values supported by the table column.  So the
sequence can no longer overflow the table column.

This also makes monitoring for sequence exhaustion/wraparound easier,
which currently requires various contortions to cross-reference the
sequences with the table columns they are used with.

This commit also effectively reverts the pg_sequence column reordering
in f3b421da5f, because the new seqtypid
column allows us to fill the hole in the struct and create a more
natural overall column ordering.

Reviewed-by: Steve Singer <steve@ssinger.info>
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
This commit is contained in:
Peter Eisentraut
2017-02-10 15:12:32 -05:00
parent 9401883a7a
commit 2ea5b06c7a
18 changed files with 274 additions and 99 deletions
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36
doc/src/sgml/ref/create_sequence.sgml
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@@ -21,7 +21,9 @@ PostgreSQL documentation
<refsynopsisdiv>
<synopsis>
CREATE [ TEMPORARY | TEMP ] SEQUENCE [ IF NOT EXISTS ] <replaceable class="parameter">name</replaceable> [ INCREMENT [ BY ] <replaceable class="parameter">increment</replaceable> ]
CREATE [ TEMPORARY | TEMP ] SEQUENCE [ IF NOT EXISTS ] <replaceable class="parameter">name</replaceable>
[ AS <replaceable class="parameter">data_type</replaceable> ]
[ INCREMENT [ BY ] <replaceable class="parameter">increment</replaceable> ]
[ MINVALUE <replaceable class="parameter">minvalue</replaceable> | NO MINVALUE ] [ MAXVALUE <replaceable class="parameter">maxvalue</replaceable> | NO MAXVALUE ]
[ START [ WITH ] <replaceable class="parameter">start</replaceable> ] [ CACHE <replaceable class="parameter">cache</replaceable> ] [ [ NO ] CYCLE ]
[ OWNED BY { <replaceable class="parameter">table_name</replaceable>.<replaceable class="parameter">column_name</replaceable> | NONE } ]
@@ -110,6 +112,21 @@ SELECT * FROM <replaceable>name</replaceable>;
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">data_type</replaceable></term>
<listitem>
<para>
The optional
clause <literal>AS <replaceable class="parameter">data_type</replaceable></literal>
specifies the data type of the sequence. Valid types are
are <literal>smallint</literal>, <literal>integer</literal>,
and <literal>bigint</literal>. <literal>bigint</literal> is the
default. The data type determines the default minimum and maximum
values of the sequence.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">increment</replaceable></term>
<listitem>
@@ -132,9 +149,8 @@ SELECT * FROM <replaceable>name</replaceable>;
class="parameter">minvalue</replaceable></literal> determines
the minimum value a sequence can generate. If this clause is not
supplied or <option>NO MINVALUE</option> is specified, then
defaults will be used. The defaults are 1 and
-2<superscript>63</> for ascending and descending sequences,
respectively.
defaults will be used. The default for an ascending sequence is 1. The
default for a descending sequence is the minimum value of the data type.
</para>
</listitem>
</varlistentry>
@@ -148,9 +164,9 @@ SELECT * FROM <replaceable>name</replaceable>;
class="parameter">maxvalue</replaceable></literal> determines
the maximum value for the sequence. If this clause is not
supplied or <option>NO MAXVALUE</option> is specified, then
default values will be used. The defaults are
2<superscript>63</>-1 and -1 for ascending and descending
sequences, respectively.
default values will be used. The default for an ascending sequence is
the maximum value of the data type. The default for a descending
sequence is -1.
</para>
</listitem>
</varlistentry>
@@ -347,12 +363,6 @@ END;
<command>CREATE SEQUENCE</command> conforms to the <acronym>SQL</acronym>
standard, with the following exceptions:
<itemizedlist>
<listitem>
<para>
The standard's <literal>AS <replaceable>data_type</></literal> expression is not
supported.
</para>
</listitem>
<listitem>
<para>
Obtaining the next value is done using the <function>nextval()</>