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Support range data types.

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Selectivity estimation functions are missing for some range type operators,
which is a TODO.

Jeff Davis
This commit is contained in:
Heikki Linnakangas
2011-11-03 13:16:28 +02:00
parent 4334289186
commit 4429f6a9e3
58 changed files with 6718 additions and 103 deletions
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61
doc/src/sgml/ref/create_type.sgml
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@@ -27,6 +27,15 @@ CREATE TYPE <replaceable class="parameter">name</replaceable> AS
CREATE TYPE <replaceable class="parameter">name</replaceable> AS ENUM
( [ '<replaceable class="parameter">label</replaceable>' [, ... ] ] )
CREATE TYPE <replaceable class="parameter">name</replaceable> AS RANGE (
SUBTYPE = <replaceable class="parameter">subtype</replaceable>,
[ , SUBTYPE_OPCLASS = <replaceable class="parameter">subtype_operator_class</replaceable> ]
[ , SUBTYPE_DIFF = <replaceable class="parameter">subtype_diff_function</replaceable> ]
[ , CANONICAL = <replaceable class="parameter">canonical_function</replaceable> ]
[ , ANALYZE = <replaceable class="parameter">analyze_function</replaceable> ]
[ , COLLATION = <replaceable class="parameter">collation</replaceable> ]
)
CREATE TYPE <replaceable class="parameter">name</replaceable> (
INPUT = <replaceable class="parameter">input_function</replaceable>,
OUTPUT = <replaceable class="parameter">output_function</replaceable>
@@ -98,11 +107,61 @@ CREATE TYPE <replaceable class="parameter">name</replaceable>
</para>
</refsect2>
<refsect2 id="SQL-CREATETYPE-RANGE">
<title>Range Types</title>
<para>
The third form of <command>CREATE TYPE</command> creates a new
range type, as described in <xref linkend="rangetypes">.
</para>
<para>
The <replaceable class="parameter">subtype</replaceable> parameter
can be any type with an associated btree opclass (uses the type's
default btree operator class unless specified with
<replaceable class="parameter">subtype_operator_class</replaceable>).
</para>
<para>
The <replaceable class="parameter">subtype_diff</replaceable>
function takes two values of type
<replaceable class="parameter">subtype</replaceable> as argument, and
returns the distance between the two values as
<type>double precision</type>. This function is used for GiST indexing
(see <xref linkend="gist"> for more information), and should be provided
for efficiency.
</para>
<para>
The <replaceable class="parameter">canonical</replaceable>
function takes an argument and returns a value, both of the same
type being defined. This is used to convert the range value to a
canonical form, when applicable. See <xref linkend="rangetypes">
for more information. To define
a <replaceable class="parameter">canonical</replaceable> function,
you must first create a <firstterm>shell type</>, which is a
placeholder type that has no properties except a name and an
owner. This is done by issuing the command <literal>CREATE TYPE
<replaceable>name</></literal>, with no additional parameters.
</para>
<para>
The <replaceable class="parameter">analyze</replaceable>
function is the same as for creating a base type.
</para>
<para>
The <replaceable class="parameter">collation</replaceable> option
specifies the collation used when determining the total order for
the range.
</para>
</refsect2>
<refsect2>
<title>Base Types</title>
<para>
The third form of <command>CREATE TYPE</command> creates a new base type
The fourth form of <command>CREATE TYPE</command> creates a new base type
(scalar type). To create a new base type, you must be a superuser.
(This restriction is made because an erroneous type definition could
confuse or even crash the server.)