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Support type modifiers for user-defined types, and pull most knowledge

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about typmod representation for standard types out into type-specific
typmod I/O functions.  Teodor Sigaev, with some editorialization by
Tom Lane.
This commit is contained in:
Tom Lane
2006-12-30 21:21:56 +00:00
parent 24b1f14eae
commit 5725b9d9af
47 changed files with 1628 additions and 685 deletions
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64
doc/src/sgml/ref/create_type.sgml
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@@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/create_type.sgml,v 1.65 2006/12/23 01:28:09 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/create_type.sgml,v 1.66 2006/12/30 21:21:52 tgl Exp $
PostgreSQL documentation
-->
@@ -28,6 +28,8 @@ CREATE TYPE <replaceable class="parameter">name</replaceable> (
OUTPUT = <replaceable class="parameter">output_function</replaceable>
[ , RECEIVE = <replaceable class="parameter">receive_function</replaceable> ]
[ , SEND = <replaceable class="parameter">send_function</replaceable> ]
[ , TYPMOD_IN = <replaceable class="parameter">type_modifier_input_function</replaceable> ]
[ , TYPMOD_OUT = <replaceable class="parameter">type_modifier_output_function</replaceable> ]
[ , ANALYZE = <replaceable class="parameter">analyze_function</replaceable> ]
[ , INTERNALLENGTH = { <replaceable class="parameter">internallength</replaceable> | VARIABLE } ]
[ , PASSEDBYVALUE ]
@@ -83,12 +85,14 @@ CREATE TYPE <replaceable class="parameter">name</replaceable>
(scalar type). The parameters may appear in any order, not only that
illustrated above, and most are optional. You must register
two or more functions (using <command>CREATE FUNCTION</command>) before
defining the type. The support functions
defining the type. The support functions
<replaceable class="parameter">input_function</replaceable> and
<replaceable class="parameter">output_function</replaceable>
are required, while the functions
<replaceable class="parameter">receive_function</replaceable>,
<replaceable class="parameter">send_function</replaceable> and
<replaceable class="parameter">send_function</replaceable>,
<replaceable class="parameter">type_modifier_input_function</replaceable>,
<replaceable class="parameter">type_modifier_output_function</replaceable> and
<replaceable class="parameter">analyze_function</replaceable>
are optional. Generally these functions have to be coded in C
or another low-level language.
@@ -169,6 +173,34 @@ CREATE TYPE <replaceable class="parameter">name</replaceable>
used normally.
</para>
<para>
The optional
<replaceable class="parameter">type_modifier_input_function</replaceable>
and <replaceable class="parameter">type_modifier_output_function</replaceable>
are needed if the type supports modifiers, that is optional constraints
attached to a type declaration, such as <literal>char(5)</> or
<literal>numeric(30,2)</>. <productname>PostgreSQL</productname> allows
user-defined types to take one or more integer constants as modifiers;
however, this information must be capable of being packed into a single
non-negative integer value for storage in the system catalogs. The
<replaceable class="parameter">type_modifier_input_function</replaceable>
is passed the declared modifier(s) in the form of an <type>integer</>
array. It must check the values for validity (throwing an error if they
are wrong), and if they are correct, return a single non-negative
<type>integer</> value that will be stored as the column <quote>typmod</>.
Type modifiers will be rejected if the type does not have a
<replaceable class="parameter">type_modifier_input_function</replaceable>.
The <replaceable class="parameter">type_modifier_output_function</replaceable>
converts the internal integer typmod value back to the correct form for
user display. It must return a <type>cstring</> value that is the exact
string to append to the type name; for example <type>numeric</>'s
function might return <literal>(30,2)</>.
It is allowed to omit the
<replaceable class="parameter">type_modifier_output_function</replaceable>,
in which case the default display format is just the stored typmod value
enclosed in parentheses.
</para>
<para>
The optional <replaceable class="parameter">analyze_function</replaceable>
performs type-specific statistics collection for columns of the data type.
@@ -265,7 +297,7 @@ CREATE TYPE <replaceable class="parameter">name</replaceable>
<title>Array Types</title>
<para>
Whenever a user-defined base data type is created,
Whenever a user-defined base data type is created,
<productname>PostgreSQL</productname> automatically creates an
associated array type, whose name consists of the base type's
name prepended with an underscore. The parser understands this
@@ -298,7 +330,7 @@ CREATE TYPE <replaceable class="parameter">name</replaceable>
</para>
</refsect2>
</refsect1>
<refsect1>
<title>Parameters</title>
@@ -371,6 +403,26 @@ CREATE TYPE <replaceable class="parameter">name</replaceable>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">type_modifier_input_function</replaceable></term>
<listitem>
<para>
The name of a function that converts numeric modifier(s) for the type
into internal form.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">type_modifier_output_function</replaceable></term>
<listitem>
<para>
The name of a function that converts the internal form of the type's
modifier(s) to external textual form.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">analyze_function</replaceable></term>
<listitem>
@@ -499,7 +551,7 @@ CREATE TYPE <replaceable class="parameter">name</replaceable>
</para>
</refsect1>
<refsect1>
<title>Examples</title>