1999-07-22 17:09:15 +02:00
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/ref/create_type.sgml,v 1.81 2010/03/21 02:24:29 momjian Exp $
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2001-12-08 04:24:40 +01:00
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PostgreSQL documentation
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1999-07-22 17:09:15 +02:00
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-->
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1999-07-06 19:16:42 +02:00
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<refentry id="SQL-CREATETYPE">
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<refmeta>
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2002-04-21 21:02:39 +02:00
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<refentrytitle id="sql-createtype-title">CREATE TYPE</refentrytitle>
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2008-11-14 11:22:48 +01:00
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<manvolnum>7</manvolnum>
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1999-07-06 19:16:42 +02:00
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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2003-04-22 12:08:08 +02:00
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1999-07-06 19:16:42 +02:00
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<refnamediv>
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<refname>CREATE TYPE</refname>
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<refpurpose>define a new data type</refpurpose>
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1998-12-29 03:24:47 +01:00
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</refnamediv>
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2003-04-22 12:08:08 +02:00
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2003-08-31 19:32:24 +02:00
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<indexterm zone="sql-createtype">
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<primary>CREATE TYPE</primary>
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</indexterm>
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1999-07-06 19:16:42 +02:00
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<refsynopsisdiv>
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2003-04-22 12:08:08 +02:00
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<synopsis>
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2003-09-22 02:16:58 +02:00
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CREATE TYPE <replaceable class="parameter">name</replaceable> AS
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2003-05-09 00:19:58 +02:00
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( <replaceable class="PARAMETER">attribute_name</replaceable> <replaceable class="PARAMETER">data_type</replaceable> [, ... ] )
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2007-04-02 05:49:42 +02:00
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CREATE TYPE <replaceable class="parameter">name</replaceable> AS ENUM
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2009-12-26 17:55:21 +01:00
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( [ '<replaceable class="parameter">label</replaceable>' [, ... ] ] )
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2003-09-22 02:16:58 +02:00
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CREATE TYPE <replaceable class="parameter">name</replaceable> (
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INPUT = <replaceable class="parameter">input_function</replaceable>,
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OUTPUT = <replaceable class="parameter">output_function</replaceable>
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[ , RECEIVE = <replaceable class="parameter">receive_function</replaceable> ]
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[ , SEND = <replaceable class="parameter">send_function</replaceable> ]
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2006-12-30 22:21:56 +01:00
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[ , TYPMOD_IN = <replaceable class="parameter">type_modifier_input_function</replaceable> ]
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[ , TYPMOD_OUT = <replaceable class="parameter">type_modifier_output_function</replaceable> ]
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2004-02-13 00:41:04 +01:00
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[ , ANALYZE = <replaceable class="parameter">analyze_function</replaceable> ]
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2003-05-09 00:19:58 +02:00
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[ , INTERNALLENGTH = { <replaceable class="parameter">internallength</replaceable> | VARIABLE } ]
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2000-08-25 01:36:29 +02:00
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[ , PASSEDBYVALUE ]
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[ , ALIGNMENT = <replaceable class="parameter">alignment</replaceable> ]
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[ , STORAGE = <replaceable class="parameter">storage</replaceable> ]
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2008-11-30 20:01:29 +01:00
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[ , LIKE = <replaceable class="parameter">like_type</replaceable> ]
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Replace the hard-wired type knowledge in TypeCategory() and IsPreferredType()
with system catalog lookups, as was foreseen to be necessary almost since
their creation. Instead put the information into two new pg_type columns,
typcategory and typispreferred. Add support for setting these when
creating a user-defined base type.
The category column is just a "char" (i.e. a poor man's enum), allowing
a crude form of user extensibility of the category list: just use an
otherwise-unused character. This seems sufficient for foreseen uses,
but we could upgrade to having an actual category catalog someday, if
there proves to be a huge demand for custom type categories.
In this patch I have attempted to hew exactly to the behavior of the
previous hardwired logic, except for introducing new type categories for
arrays, composites, and enums. In particular the default preferred state
for user-defined types remains TRUE. That seems worth revisiting, but it
should be done as a separate patch from introducing the infrastructure.
Likewise, any adjustment of the standard set of categories should be done
separately.
2008-07-30 19:05:05 +02:00
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[ , CATEGORY = <replaceable class="parameter">category</replaceable> ]
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[ , PREFERRED = <replaceable class="parameter">preferred</replaceable> ]
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2003-05-09 00:19:58 +02:00
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[ , DEFAULT = <replaceable class="parameter">default</replaceable> ]
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[ , ELEMENT = <replaceable class="parameter">element</replaceable> ]
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[ , DELIMITER = <replaceable class="parameter">delimiter</replaceable> ]
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2000-08-25 01:36:29 +02:00
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)
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2006-02-28 23:37:27 +01:00
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CREATE TYPE <replaceable class="parameter">name</replaceable>
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2003-04-22 12:08:08 +02:00
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</synopsis>
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1999-07-06 19:16:42 +02:00
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</refsynopsisdiv>
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2003-04-22 12:08:08 +02:00
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<refsect1>
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<title>Description</title>
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<para>
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2003-04-22 12:08:08 +02:00
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<command>CREATE TYPE</command> registers a new data type for use in
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2005-01-04 01:39:53 +01:00
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the current database. The user who defines a type becomes its
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2003-04-22 12:08:08 +02:00
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owner.
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2002-04-23 04:07:16 +02:00
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</para>
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<para>
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2003-04-22 12:08:08 +02:00
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If a schema name is given then the type is created in the specified
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schema. Otherwise it is created in the current schema. The type
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name must be distinct from the name of any existing type or domain
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in the same schema. (Because tables have associated data types,
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the type name must also be distinct from the name of any existing
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table in the same schema.)
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1998-07-29 08:23:26 +02:00
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</para>
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1999-07-22 17:09:15 +02:00
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2003-05-09 00:19:58 +02:00
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<refsect2>
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<title>Composite Types</title>
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<para>
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The first form of <command>CREATE TYPE</command>
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creates a composite type.
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The composite type is specified by a list of attribute names and data types.
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This is essentially the same as the row type
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of a table, but using <command>CREATE TYPE</command> avoids the need to
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create an actual table when all that is wanted is to define a type.
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2005-01-04 01:39:53 +01:00
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A stand-alone composite type is useful as the argument or return type of a
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function.
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2003-05-09 00:19:58 +02:00
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</para>
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</refsect2>
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2010-03-21 03:24:29 +01:00
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<refsect2 id="SQL-CREATETYPE-enum">
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2007-04-02 05:49:42 +02:00
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<title>Enumerated Types</title>
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<para>
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The second form of <command>CREATE TYPE</command> creates an enumerated
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(enum) type, as described in <xref linkend="datatype-enum">.
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Enum types take a list of one or more quoted labels, each of which
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must be less than <symbol>NAMEDATALEN</symbol> bytes long (64 in a standard
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<productname>PostgreSQL</productname> build).
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</para>
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</refsect2>
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2002-08-29 02:17:06 +02:00
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<refsect2>
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<title>Base Types</title>
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1999-07-06 19:16:42 +02:00
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<para>
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2007-04-02 05:49:42 +02:00
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The third form of <command>CREATE TYPE</command> creates a new base type
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2008-07-31 18:27:16 +02:00
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(scalar type). To create a new base type, you must be a superuser.
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(This restriction is made because an erroneous type definition could
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confuse or even crash the server.)
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</para>
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<para>
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The parameters can appear in any order, not only that
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2003-05-09 00:19:58 +02:00
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illustrated above, and most are optional. You must register
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two or more functions (using <command>CREATE FUNCTION</command>) before
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2006-12-30 22:21:56 +01:00
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defining the type. The support functions
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2003-05-09 00:19:58 +02:00
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<replaceable class="parameter">input_function</replaceable> and
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<replaceable class="parameter">output_function</replaceable>
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are required, while the functions
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2004-02-13 00:41:04 +01:00
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<replaceable class="parameter">receive_function</replaceable>,
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2006-12-30 22:21:56 +01:00
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<replaceable class="parameter">send_function</replaceable>,
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<replaceable class="parameter">type_modifier_input_function</replaceable>,
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<replaceable class="parameter">type_modifier_output_function</replaceable> and
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2004-02-13 00:41:04 +01:00
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<replaceable class="parameter">analyze_function</replaceable>
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2003-05-09 00:19:58 +02:00
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are optional. Generally these functions have to be coded in C
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or another low-level language.
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</para>
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<para>
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The <replaceable class="parameter">input_function</replaceable>
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converts the type's external textual representation to the internal
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2006-04-04 21:35:37 +02:00
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representation used by the operators and functions defined for the type.
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1998-07-29 08:23:26 +02:00
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<replaceable class="parameter">output_function</replaceable>
|
Update reference documentation on may/can/might:
Standard English uses "may", "can", and "might" in different ways:
may - permission, "You may borrow my rake."
can - ability, "I can lift that log."
might - possibility, "It might rain today."
Unfortunately, in conversational English, their use is often mixed, as
in, "You may use this variable to do X", when in fact, "can" is a better
choice. Similarly, "It may crash" is better stated, "It might crash".
2007-02-01 00:26:05 +01:00
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performs the reverse transformation. The input function can be
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2002-08-22 02:01:51 +02:00
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declared as taking one argument of type <type>cstring</type>,
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2001-11-03 22:42:47 +01:00
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or as taking three arguments of types
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2003-04-22 12:08:08 +02:00
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<type>cstring</type>, <type>oid</type>, <type>integer</type>.
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The first argument is the input text as a C string, the second
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2005-08-12 23:49:47 +02:00
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argument is the type's own OID (except for array types, which instead
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receive their element type's OID),
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2005-01-04 01:39:53 +01:00
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and the third is the <literal>typmod</> of the destination column, if known
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(-1 will be passed if not).
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2005-05-01 20:56:19 +02:00
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The input function must return a value of the data type itself.
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2006-04-04 21:35:37 +02:00
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Usually, an input function should be declared STRICT; if it is not,
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it will be called with a NULL first parameter when reading a NULL
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input value. The function must still return NULL in this case, unless
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it raises an error.
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(This case is mainly meant to support domain input functions, which
|
Update reference documentation on may/can/might:
Standard English uses "may", "can", and "might" in different ways:
may - permission, "You may borrow my rake."
can - ability, "I can lift that log."
might - possibility, "It might rain today."
Unfortunately, in conversational English, their use is often mixed, as
in, "You may use this variable to do X", when in fact, "can" is a better
choice. Similarly, "It may crash" is better stated, "It might crash".
2007-02-01 00:26:05 +01:00
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might need to reject NULL inputs.)
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2005-05-01 20:56:19 +02:00
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The output function must be
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declared as taking one argument of the new data type.
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The output function must return type <type>cstring</type>.
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2006-04-04 21:35:37 +02:00
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Output functions are not invoked for NULL values.
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1998-07-29 08:23:26 +02:00
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</para>
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1999-07-22 17:09:15 +02:00
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2003-05-09 00:19:58 +02:00
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<para>
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The optional <replaceable class="parameter">receive_function</replaceable>
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converts the type's external binary representation to the internal
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representation. If this function is not supplied, the type cannot
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participate in binary input. The binary representation should be
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chosen to be cheap to convert to internal form, while being reasonably
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2003-11-01 02:56:29 +01:00
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portable. (For example, the standard integer data types use network
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2003-05-09 00:19:58 +02:00
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byte order as the external binary representation, while the internal
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representation is in the machine's native byte order.) The receive
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function should perform adequate checking to ensure that the value is
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valid.
|
Update reference documentation on may/can/might:
Standard English uses "may", "can", and "might" in different ways:
may - permission, "You may borrow my rake."
can - ability, "I can lift that log."
might - possibility, "It might rain today."
Unfortunately, in conversational English, their use is often mixed, as
in, "You may use this variable to do X", when in fact, "can" is a better
choice. Similarly, "It may crash" is better stated, "It might crash".
2007-02-01 00:26:05 +01:00
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The receive function can be declared as taking one argument of type
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2005-07-10 23:14:00 +02:00
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<type>internal</type>, or as taking three arguments of types
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<type>internal</type>, <type>oid</type>, <type>integer</type>.
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The first argument is a pointer to a <type>StringInfo</type> buffer
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holding the received byte string; the optional arguments are the
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same as for the text input function.
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The receive function must return a value of the data type itself.
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2006-04-04 21:35:37 +02:00
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Usually, a receive function should be declared STRICT; if it is not,
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it will be called with a NULL first parameter when reading a NULL
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input value. The function must still return NULL in this case, unless
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it raises an error.
|
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(This case is mainly meant to support domain receive functions, which
|
Update reference documentation on may/can/might:
Standard English uses "may", "can", and "might" in different ways:
may - permission, "You may borrow my rake."
can - ability, "I can lift that log."
might - possibility, "It might rain today."
Unfortunately, in conversational English, their use is often mixed, as
in, "You may use this variable to do X", when in fact, "can" is a better
choice. Similarly, "It may crash" is better stated, "It might crash".
2007-02-01 00:26:05 +01:00
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might need to reject NULL inputs.)
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2005-07-10 23:14:00 +02:00
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Similarly, the optional
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2003-05-09 00:19:58 +02:00
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<replaceable class="parameter">send_function</replaceable> converts
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from the internal representation to the external binary representation.
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If this function is not supplied, the type cannot participate in binary
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2005-05-01 20:56:19 +02:00
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output. The send function must be
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declared as taking one argument of the new data type.
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2003-05-10 01:01:45 +02:00
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The send function must return type <type>bytea</type>.
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2006-04-04 21:35:37 +02:00
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Send functions are not invoked for NULL values.
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2003-05-09 00:19:58 +02:00
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</para>
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2002-08-22 02:01:51 +02:00
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<para>
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You should at this point be wondering how the input and output functions
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2006-02-28 23:37:27 +01:00
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can be declared to have results or arguments of the new type, when they
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have to be created before the new type can be created. The answer is that
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the type should first be defined as a <firstterm>shell type</>, which is a
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placeholder type that has no properties except a name and an owner. This
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is done by issuing the command <literal>CREATE TYPE
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<replaceable>name</></literal>, with no additional parameters. Then the
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I/O functions can be defined referencing the shell type. Finally,
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<command>CREATE TYPE</> with a full definition replaces the shell entry
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with a complete, valid type definition, after which the new type can be
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used normally.
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2002-08-22 02:01:51 +02:00
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</para>
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2006-12-30 22:21:56 +01:00
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<para>
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The optional
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<replaceable class="parameter">type_modifier_input_function</replaceable>
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and <replaceable class="parameter">type_modifier_output_function</replaceable>
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are needed if the type supports modifiers, that is optional constraints
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attached to a type declaration, such as <literal>char(5)</> or
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<literal>numeric(30,2)</>. <productname>PostgreSQL</productname> allows
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2007-06-15 22:56:52 +02:00
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user-defined types to take one or more simple constants or identifiers as
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2008-05-27 20:05:13 +02:00
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modifiers. However, this information must be capable of being packed into a
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2007-06-15 22:56:52 +02:00
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single non-negative integer value for storage in the system catalogs. The
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2006-12-30 22:21:56 +01:00
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<replaceable class="parameter">type_modifier_input_function</replaceable>
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2007-06-15 22:56:52 +02:00
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is passed the declared modifier(s) in the form of a <type>cstring</>
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2006-12-30 22:21:56 +01:00
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array. It must check the values for validity (throwing an error if they
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are wrong), and if they are correct, return a single non-negative
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<type>integer</> value that will be stored as the column <quote>typmod</>.
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Type modifiers will be rejected if the type does not have a
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<replaceable class="parameter">type_modifier_input_function</replaceable>.
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The <replaceable class="parameter">type_modifier_output_function</replaceable>
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converts the internal integer typmod value back to the correct form for
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user display. It must return a <type>cstring</> value that is the exact
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string to append to the type name; for example <type>numeric</>'s
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function might return <literal>(30,2)</>.
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It is allowed to omit the
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<replaceable class="parameter">type_modifier_output_function</replaceable>,
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2008-05-27 20:05:13 +02:00
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in which case the default display format is just the stored typmod integer
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value enclosed in parentheses.
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2006-12-30 22:21:56 +01:00
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</para>
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2004-02-13 00:41:04 +01:00
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<para>
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The optional <replaceable class="parameter">analyze_function</replaceable>
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performs type-specific statistics collection for columns of the data type.
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By default, <command>ANALYZE</> will attempt to gather statistics using
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|
|
the type's <quote>equals</> and <quote>less-than</> operators, if there
|
|
|
|
is a default b-tree operator class for the type. For non-scalar types
|
|
|
|
this behavior is likely to be unsuitable, so it can be overridden by
|
|
|
|
specifying a custom analysis function. The analysis function must be
|
|
|
|
declared to take a single argument of type <type>internal</>, and return
|
|
|
|
a <type>boolean</> result. The detailed API for analysis functions appears
|
|
|
|
in <filename>src/include/commands/vacuum.h</>.
|
|
|
|
</para>
|
|
|
|
|
2002-08-22 02:01:51 +02:00
|
|
|
<para>
|
2003-05-09 00:19:58 +02:00
|
|
|
While the details of the new type's internal representation are only
|
|
|
|
known to the I/O functions and other functions you create to work with
|
|
|
|
the type, there are several properties of the internal representation
|
|
|
|
that must be declared to <productname>PostgreSQL</productname>.
|
|
|
|
Foremost of these is
|
|
|
|
<replaceable class="parameter">internallength</replaceable>.
|
2003-04-22 12:08:08 +02:00
|
|
|
Base data types can be fixed-length, in which case
|
1998-07-29 08:23:26 +02:00
|
|
|
<replaceable class="parameter">internallength</replaceable> is a
|
2001-11-03 22:42:47 +01:00
|
|
|
positive integer, or variable length, indicated by setting
|
1998-07-29 08:23:26 +02:00
|
|
|
<replaceable class="parameter">internallength</replaceable>
|
2003-04-22 12:08:08 +02:00
|
|
|
to <literal>VARIABLE</literal>. (Internally, this is represented
|
2002-09-21 20:32:54 +02:00
|
|
|
by setting <literal>typlen</> to -1.) The internal representation of all
|
2003-04-22 12:08:08 +02:00
|
|
|
variable-length types must start with a 4-byte integer giving the total
|
2001-11-03 22:42:47 +01:00
|
|
|
length of this value of the type.
|
|
|
|
</para>
|
|
|
|
|
1999-07-06 19:16:42 +02:00
|
|
|
<para>
|
2003-04-22 12:08:08 +02:00
|
|
|
The optional flag <literal>PASSEDBYVALUE</literal> indicates that
|
2003-05-09 00:19:58 +02:00
|
|
|
values of this data type are passed by value, rather than by
|
Update reference documentation on may/can/might:
Standard English uses "may", "can", and "might" in different ways:
may - permission, "You may borrow my rake."
can - ability, "I can lift that log."
might - possibility, "It might rain today."
Unfortunately, in conversational English, their use is often mixed, as
in, "You may use this variable to do X", when in fact, "can" is a better
choice. Similarly, "It may crash" is better stated, "It might crash".
2007-02-01 00:26:05 +01:00
|
|
|
reference. You cannot pass by value types whose internal
|
2003-04-22 12:08:08 +02:00
|
|
|
representation is larger than the size of the <type>Datum</> type
|
|
|
|
(4 bytes on most machines, 8 bytes on a few).
|
2001-11-03 22:42:47 +01:00
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
2003-04-22 12:08:08 +02:00
|
|
|
The <replaceable class="parameter">alignment</replaceable> parameter
|
2002-01-20 23:19:57 +01:00
|
|
|
specifies the storage alignment required for the data type. The
|
2001-11-03 22:42:47 +01:00
|
|
|
allowed values equate to alignment on 1, 2, 4, or 8 byte boundaries.
|
|
|
|
Note that variable-length types must have an alignment of at least
|
|
|
|
4, since they necessarily contain an <type>int4</> as their first component.
|
1998-07-29 08:23:26 +02:00
|
|
|
</para>
|
1999-07-22 17:09:15 +02:00
|
|
|
|
2000-08-25 01:36:29 +02:00
|
|
|
<para>
|
2003-04-22 12:08:08 +02:00
|
|
|
The <replaceable class="parameter">storage</replaceable> parameter
|
|
|
|
allows selection of storage strategies for variable-length data
|
|
|
|
types. (Only <literal>plain</literal> is allowed for fixed-length
|
|
|
|
types.) <literal>plain</literal> specifies that data of the type
|
|
|
|
will always be stored in-line and not compressed.
|
|
|
|
<literal>extended</literal> specifies that the system will first
|
|
|
|
try to compress a long data value, and will move the value out of
|
2000-08-25 01:36:29 +02:00
|
|
|
the main table row if it's still too long.
|
2003-04-22 12:08:08 +02:00
|
|
|
<literal>external</literal> allows the value to be moved out of the
|
|
|
|
main table, but the system will not try to compress it.
|
|
|
|
<literal>main</literal> allows compression, but discourages moving
|
|
|
|
the value out of the main table. (Data items with this storage
|
Update reference documentation on may/can/might:
Standard English uses "may", "can", and "might" in different ways:
may - permission, "You may borrow my rake."
can - ability, "I can lift that log."
might - possibility, "It might rain today."
Unfortunately, in conversational English, their use is often mixed, as
in, "You may use this variable to do X", when in fact, "can" is a better
choice. Similarly, "It may crash" is better stated, "It might crash".
2007-02-01 00:26:05 +01:00
|
|
|
strategy might still be moved out of the main table if there is no
|
2003-04-22 12:08:08 +02:00
|
|
|
other way to make a row fit, but they will be kept in the main
|
|
|
|
table preferentially over <literal>extended</literal> and
|
|
|
|
<literal>external</literal> items.)
|
2000-08-25 01:36:29 +02:00
|
|
|
</para>
|
2002-08-29 02:17:06 +02:00
|
|
|
|
2008-11-30 20:01:29 +01:00
|
|
|
<para>
|
|
|
|
The <replaceable class="parameter">like_type</replaceable> parameter
|
|
|
|
provides an alternative method for specifying the basic representation
|
|
|
|
properties of a data type: copy them from some existing type. The values of
|
|
|
|
<replaceable class="parameter">internallength</replaceable>,
|
|
|
|
<replaceable class="parameter">passedbyvalue</replaceable>,
|
|
|
|
<replaceable class="parameter">alignment</replaceable>, and
|
|
|
|
<replaceable class="parameter">storage</replaceable> are copied from the
|
|
|
|
named type. (It is possible, though usually undesirable, to override
|
|
|
|
some of these values by specifying them along with the <literal>LIKE</>
|
|
|
|
clause.) Specifying representation this way is especially useful when
|
|
|
|
the low-level implementation of the new type <quote>piggybacks</> on an
|
|
|
|
existing type in some fashion.
|
|
|
|
</para>
|
|
|
|
|
Replace the hard-wired type knowledge in TypeCategory() and IsPreferredType()
with system catalog lookups, as was foreseen to be necessary almost since
their creation. Instead put the information into two new pg_type columns,
typcategory and typispreferred. Add support for setting these when
creating a user-defined base type.
The category column is just a "char" (i.e. a poor man's enum), allowing
a crude form of user extensibility of the category list: just use an
otherwise-unused character. This seems sufficient for foreseen uses,
but we could upgrade to having an actual category catalog someday, if
there proves to be a huge demand for custom type categories.
In this patch I have attempted to hew exactly to the behavior of the
previous hardwired logic, except for introducing new type categories for
arrays, composites, and enums. In particular the default preferred state
for user-defined types remains TRUE. That seems worth revisiting, but it
should be done as a separate patch from introducing the infrastructure.
Likewise, any adjustment of the standard set of categories should be done
separately.
2008-07-30 19:05:05 +02:00
|
|
|
<para>
|
|
|
|
The <replaceable class="parameter">category</replaceable> and
|
|
|
|
<replaceable class="parameter">preferred</replaceable> parameters can be
|
|
|
|
used to help control which implicit cast will be applied in ambiguous
|
|
|
|
situations. Each data type belongs to a category named by a single ASCII
|
|
|
|
character, and each type is either <quote>preferred</> or not within its
|
|
|
|
category. The parser will prefer casting to preferred types (but only from
|
|
|
|
other types within the same category) when this rule is helpful in
|
|
|
|
resolving overloaded functions or operators. For more details see <xref
|
|
|
|
linkend="typeconv">. For types that have no implicit casts to or from any
|
|
|
|
other types, it is sufficient to leave these settings at the defaults.
|
|
|
|
However, for a group of related types that have implicit casts, it is often
|
|
|
|
helpful to mark them all as belonging to a category and select one or two
|
|
|
|
of the <quote>most general</> types as being preferred within the category.
|
|
|
|
The <replaceable class="parameter">category</replaceable> parameter is
|
|
|
|
especially useful when adding a user-defined type to an existing built-in
|
|
|
|
category, such as the numeric or string types. However, it is also
|
|
|
|
possible to create new entirely-user-defined type categories. Select any
|
|
|
|
ASCII character other than an upper-case letter to name such a category.
|
|
|
|
</para>
|
|
|
|
|
2003-05-09 00:19:58 +02:00
|
|
|
<para>
|
Update reference documentation on may/can/might:
Standard English uses "may", "can", and "might" in different ways:
may - permission, "You may borrow my rake."
can - ability, "I can lift that log."
might - possibility, "It might rain today."
Unfortunately, in conversational English, their use is often mixed, as
in, "You may use this variable to do X", when in fact, "can" is a better
choice. Similarly, "It may crash" is better stated, "It might crash".
2007-02-01 00:26:05 +01:00
|
|
|
A default value can be specified, in case a user wants columns of the
|
2003-05-09 00:19:58 +02:00
|
|
|
data type to default to something other than the null value.
|
|
|
|
Specify the default with the <literal>DEFAULT</literal> key word.
|
Update reference documentation on may/can/might:
Standard English uses "may", "can", and "might" in different ways:
may - permission, "You may borrow my rake."
can - ability, "I can lift that log."
might - possibility, "It might rain today."
Unfortunately, in conversational English, their use is often mixed, as
in, "You may use this variable to do X", when in fact, "can" is a better
choice. Similarly, "It may crash" is better stated, "It might crash".
2007-02-01 00:26:05 +01:00
|
|
|
(Such a default can be overridden by an explicit <literal>DEFAULT</literal>
|
2003-05-09 00:19:58 +02:00
|
|
|
clause attached to a particular column.)
|
|
|
|
</para>
|
2000-08-25 01:36:29 +02:00
|
|
|
|
2002-08-15 18:36:08 +02:00
|
|
|
<para>
|
2003-05-09 00:19:58 +02:00
|
|
|
To indicate that a type is an array, specify the type of the array
|
|
|
|
elements using the <literal>ELEMENT</> key word. For example, to
|
|
|
|
define an array of 4-byte integers (<type>int4</type>), specify
|
|
|
|
<literal>ELEMENT = int4</literal>. More details about array types
|
|
|
|
appear below.
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
To indicate the delimiter to be used between values in the external
|
|
|
|
representation of arrays of this type, <replaceable
|
|
|
|
class="parameter">delimiter</replaceable> can be
|
|
|
|
set to a specific character. The default delimiter is the comma
|
|
|
|
(<literal>,</literal>). Note that the delimiter is associated
|
|
|
|
with the array element type, not the array type itself.
|
2002-08-15 18:36:08 +02:00
|
|
|
</para>
|
2003-05-09 00:19:58 +02:00
|
|
|
|
2002-08-29 02:17:06 +02:00
|
|
|
</refsect2>
|
2002-08-15 18:36:08 +02:00
|
|
|
|
1998-07-29 08:23:26 +02:00
|
|
|
<refsect2>
|
|
|
|
<title>Array Types</title>
|
2001-11-03 22:42:47 +01:00
|
|
|
|
1998-07-29 08:23:26 +02:00
|
|
|
<para>
|
Support arrays of composite types, including the rowtypes of regular tables
and views (but not system catalogs, nor sequences or toast tables). Get rid
of the hardwired convention that a type's array type is named exactly "_type",
instead using a new column pg_type.typarray to provide the linkage. (It still
will be named "_type", though, except in odd corner cases such as
maximum-length type names.)
Along the way, make tracking of owner and schema dependencies for types more
uniform: a type directly created by the user has these dependencies, while a
table rowtype or auto-generated array type does not have them, but depends on
its parent object instead.
David Fetter, Andrew Dunstan, Tom Lane
2007-05-11 19:57:14 +02:00
|
|
|
Whenever a user-defined type is created,
|
2001-11-03 22:42:47 +01:00
|
|
|
<productname>PostgreSQL</productname> automatically creates an
|
|
|
|
associated array type, whose name consists of the base type's
|
Support arrays of composite types, including the rowtypes of regular tables
and views (but not system catalogs, nor sequences or toast tables). Get rid
of the hardwired convention that a type's array type is named exactly "_type",
instead using a new column pg_type.typarray to provide the linkage. (It still
will be named "_type", though, except in odd corner cases such as
maximum-length type names.)
Along the way, make tracking of owner and schema dependencies for types more
uniform: a type directly created by the user has these dependencies, while a
table rowtype or auto-generated array type does not have them, but depends on
its parent object instead.
David Fetter, Andrew Dunstan, Tom Lane
2007-05-11 19:57:14 +02:00
|
|
|
name prepended with an underscore, and truncated if necessary to keep
|
|
|
|
it less than <symbol>NAMEDATALEN</symbol> bytes long. (If the name
|
|
|
|
so generated collides with an existing type name, the process is
|
|
|
|
repeated until a non-colliding name is found.)
|
|
|
|
This implicitly-created array type is variable length and uses the
|
2001-11-03 22:42:47 +01:00
|
|
|
built-in input and output functions <literal>array_in</> and
|
Support arrays of composite types, including the rowtypes of regular tables
and views (but not system catalogs, nor sequences or toast tables). Get rid
of the hardwired convention that a type's array type is named exactly "_type",
instead using a new column pg_type.typarray to provide the linkage. (It still
will be named "_type", though, except in odd corner cases such as
maximum-length type names.)
Along the way, make tracking of owner and schema dependencies for types more
uniform: a type directly created by the user has these dependencies, while a
table rowtype or auto-generated array type does not have them, but depends on
its parent object instead.
David Fetter, Andrew Dunstan, Tom Lane
2007-05-11 19:57:14 +02:00
|
|
|
<literal>array_out</>. The array type tracks any changes in its
|
|
|
|
element type's owner or schema, and is dropped if the element type is.
|
2001-11-03 22:42:47 +01:00
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
2003-04-22 12:08:08 +02:00
|
|
|
You might reasonably ask why there is an <option>ELEMENT</>
|
|
|
|
option, if the system makes the correct array type automatically.
|
2001-11-03 22:42:47 +01:00
|
|
|
The only case where it's useful to use <option>ELEMENT</> is when you are
|
2003-04-22 12:08:08 +02:00
|
|
|
making a fixed-length type that happens to be internally an array of a number of
|
|
|
|
identical things, and you want to allow these things to be accessed
|
2001-11-03 22:42:47 +01:00
|
|
|
directly by subscripting, in addition to whatever operations you plan
|
Support arrays of composite types, including the rowtypes of regular tables
and views (but not system catalogs, nor sequences or toast tables). Get rid
of the hardwired convention that a type's array type is named exactly "_type",
instead using a new column pg_type.typarray to provide the linkage. (It still
will be named "_type", though, except in odd corner cases such as
maximum-length type names.)
Along the way, make tracking of owner and schema dependencies for types more
uniform: a type directly created by the user has these dependencies, while a
table rowtype or auto-generated array type does not have them, but depends on
its parent object instead.
David Fetter, Andrew Dunstan, Tom Lane
2007-05-11 19:57:14 +02:00
|
|
|
to provide for the type as a whole. For example, type <type>point</>
|
|
|
|
is represented as just two floating-point numbers, which it allows to be
|
|
|
|
accessed as <literal>point[0]</> and <literal>point[1]</>.
|
2001-11-03 22:42:47 +01:00
|
|
|
Note that
|
|
|
|
this facility only works for fixed-length types whose internal form
|
2003-04-22 12:08:08 +02:00
|
|
|
is exactly a sequence of identical fixed-length fields. A subscriptable
|
2001-11-03 22:42:47 +01:00
|
|
|
variable-length type must have the generalized internal representation
|
|
|
|
used by <literal>array_in</> and <literal>array_out</>.
|
|
|
|
For historical reasons (i.e., this is clearly wrong but it's far too
|
|
|
|
late to change it), subscripting of fixed-length array types starts from
|
|
|
|
zero, rather than from one as for variable-length arrays.
|
1999-07-06 19:16:42 +02:00
|
|
|
</para>
|
1998-07-29 08:23:26 +02:00
|
|
|
</refsect2>
|
|
|
|
</refsect1>
|
2006-12-30 22:21:56 +01:00
|
|
|
|
2003-04-22 12:08:08 +02:00
|
|
|
<refsect1>
|
2003-05-09 00:19:58 +02:00
|
|
|
<title>Parameters</title>
|
2003-04-22 12:08:08 +02:00
|
|
|
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry>
|
2003-09-22 02:16:58 +02:00
|
|
|
<term><replaceable class="parameter">name</replaceable></term>
|
2003-04-22 12:08:08 +02:00
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
The name (optionally schema-qualified) of a type to be created.
|
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
|
|
|
<varlistentry>
|
2003-05-09 00:19:58 +02:00
|
|
|
<term><replaceable class="parameter">attribute_name</replaceable></term>
|
2003-04-22 12:08:08 +02:00
|
|
|
<listitem>
|
|
|
|
<para>
|
2003-05-09 00:19:58 +02:00
|
|
|
The name of an attribute (column) for the composite type.
|
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
|
|
|
<varlistentry>
|
|
|
|
<term><replaceable class="parameter">data_type</replaceable></term>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
The name of an existing data type to become a column of the
|
|
|
|
composite type.
|
2003-04-22 12:08:08 +02:00
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
2007-04-02 05:49:42 +02:00
|
|
|
<varlistentry>
|
|
|
|
<term><replaceable class="parameter">label</replaceable></term>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
A string literal representing the textual label associated with
|
|
|
|
one value of an enum type.
|
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
2003-04-22 12:08:08 +02:00
|
|
|
<varlistentry>
|
|
|
|
<term><replaceable class="parameter">input_function</replaceable></term>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
The name of a function that converts data from the type's
|
2003-05-09 00:19:58 +02:00
|
|
|
external textual form to its internal form.
|
2003-04-22 12:08:08 +02:00
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
|
|
|
<varlistentry>
|
|
|
|
<term><replaceable class="parameter">output_function</replaceable></term>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
The name of a function that converts data from the type's
|
2003-05-09 00:19:58 +02:00
|
|
|
internal form to its external textual form.
|
2003-04-22 12:08:08 +02:00
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
|
|
|
<varlistentry>
|
2003-05-09 00:19:58 +02:00
|
|
|
<term><replaceable class="parameter">receive_function</replaceable></term>
|
2003-04-22 12:08:08 +02:00
|
|
|
<listitem>
|
|
|
|
<para>
|
2003-05-09 00:19:58 +02:00
|
|
|
The name of a function that converts data from the type's
|
|
|
|
external binary form to its internal form.
|
2003-04-22 12:08:08 +02:00
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
|
|
|
<varlistentry>
|
2003-05-09 00:19:58 +02:00
|
|
|
<term><replaceable class="parameter">send_function</replaceable></term>
|
2003-04-22 12:08:08 +02:00
|
|
|
<listitem>
|
|
|
|
<para>
|
2003-05-09 00:19:58 +02:00
|
|
|
The name of a function that converts data from the type's
|
|
|
|
internal form to its external binary form.
|
2003-04-22 12:08:08 +02:00
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
2006-12-30 22:21:56 +01:00
|
|
|
<varlistentry>
|
|
|
|
<term><replaceable class="parameter">type_modifier_input_function</replaceable></term>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
2008-05-27 20:05:13 +02:00
|
|
|
The name of a function that converts an array of modifier(s) for the type
|
2006-12-30 22:21:56 +01:00
|
|
|
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>
|
|
|
|
|
2004-02-13 00:41:04 +01:00
|
|
|
<varlistentry>
|
|
|
|
<term><replaceable class="parameter">analyze_function</replaceable></term>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
The name of a function that performs statistical analysis for the
|
|
|
|
data type.
|
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
2003-04-22 12:08:08 +02:00
|
|
|
<varlistentry>
|
2003-05-09 00:19:58 +02:00
|
|
|
<term><replaceable class="parameter">internallength</replaceable></term>
|
2003-04-22 12:08:08 +02:00
|
|
|
<listitem>
|
|
|
|
<para>
|
2003-05-09 00:19:58 +02:00
|
|
|
A numeric constant that specifies the length in bytes of the new
|
|
|
|
type's internal representation. The default assumption is that
|
|
|
|
it is variable-length.
|
2003-04-22 12:08:08 +02:00
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
|
|
|
<varlistentry>
|
|
|
|
<term><replaceable class="parameter">alignment</replaceable></term>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
The storage alignment requirement of the data type. If specified,
|
|
|
|
it must be <literal>char</literal>, <literal>int2</literal>,
|
|
|
|
<literal>int4</literal>, or <literal>double</literal>; the
|
|
|
|
default is <literal>int4</literal>.
|
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
|
|
|
<varlistentry>
|
|
|
|
<term><replaceable class="parameter">storage</replaceable></term>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
2003-05-09 00:19:58 +02:00
|
|
|
The storage strategy for the data type. If specified, must be
|
2003-04-22 12:08:08 +02:00
|
|
|
<literal>plain</literal>, <literal>external</literal>,
|
|
|
|
<literal>extended</literal>, or <literal>main</literal>; the
|
|
|
|
default is <literal>plain</literal>.
|
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
2008-11-30 20:01:29 +01:00
|
|
|
<varlistentry>
|
|
|
|
<term><replaceable class="parameter">like_type</replaceable></term>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
The name of an existing data type that the new type will have the
|
|
|
|
same representation as. The values of
|
|
|
|
<replaceable class="parameter">internallength</replaceable>,
|
|
|
|
<replaceable class="parameter">passedbyvalue</replaceable>,
|
|
|
|
<replaceable class="parameter">alignment</replaceable>, and
|
|
|
|
<replaceable class="parameter">storage</replaceable>
|
|
|
|
are copied from that type, unless overridden by explicit
|
|
|
|
specification elsewhere in this <command>CREATE TYPE</> command.
|
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
Replace the hard-wired type knowledge in TypeCategory() and IsPreferredType()
with system catalog lookups, as was foreseen to be necessary almost since
their creation. Instead put the information into two new pg_type columns,
typcategory and typispreferred. Add support for setting these when
creating a user-defined base type.
The category column is just a "char" (i.e. a poor man's enum), allowing
a crude form of user extensibility of the category list: just use an
otherwise-unused character. This seems sufficient for foreseen uses,
but we could upgrade to having an actual category catalog someday, if
there proves to be a huge demand for custom type categories.
In this patch I have attempted to hew exactly to the behavior of the
previous hardwired logic, except for introducing new type categories for
arrays, composites, and enums. In particular the default preferred state
for user-defined types remains TRUE. That seems worth revisiting, but it
should be done as a separate patch from introducing the infrastructure.
Likewise, any adjustment of the standard set of categories should be done
separately.
2008-07-30 19:05:05 +02:00
|
|
|
<varlistentry>
|
|
|
|
<term><replaceable class="parameter">category</replaceable></term>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
The category code (a single ASCII character) for this type.
|
|
|
|
The default is <literal>'U'</> for <quote>user-defined type</>.
|
|
|
|
Other standard category codes can be found in
|
|
|
|
<xref linkend="catalog-typcategory-table">. You may also choose
|
|
|
|
other ASCII characters in order to create custom categories.
|
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
|
|
|
<varlistentry>
|
|
|
|
<term><replaceable class="parameter">preferred</replaceable></term>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
True if this type is a preferred type within its type category,
|
2008-07-30 21:35:13 +02:00
|
|
|
else false. The default is false. Be very careful about creating
|
|
|
|
a new preferred type within an existing type category, as this
|
|
|
|
could cause surprising changes in behavior.
|
Replace the hard-wired type knowledge in TypeCategory() and IsPreferredType()
with system catalog lookups, as was foreseen to be necessary almost since
their creation. Instead put the information into two new pg_type columns,
typcategory and typispreferred. Add support for setting these when
creating a user-defined base type.
The category column is just a "char" (i.e. a poor man's enum), allowing
a crude form of user extensibility of the category list: just use an
otherwise-unused character. This seems sufficient for foreseen uses,
but we could upgrade to having an actual category catalog someday, if
there proves to be a huge demand for custom type categories.
In this patch I have attempted to hew exactly to the behavior of the
previous hardwired logic, except for introducing new type categories for
arrays, composites, and enums. In particular the default preferred state
for user-defined types remains TRUE. That seems worth revisiting, but it
should be done as a separate patch from introducing the infrastructure.
Likewise, any adjustment of the standard set of categories should be done
separately.
2008-07-30 19:05:05 +02:00
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
2003-04-22 12:08:08 +02:00
|
|
|
<varlistentry>
|
2003-05-09 00:19:58 +02:00
|
|
|
<term><replaceable class="parameter">default</replaceable></term>
|
2003-04-22 12:08:08 +02:00
|
|
|
<listitem>
|
|
|
|
<para>
|
2003-05-09 00:19:58 +02:00
|
|
|
The default value for the data type. If this is omitted, the
|
|
|
|
default is null.
|
2003-04-22 12:08:08 +02:00
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
|
|
|
<varlistentry>
|
2003-05-09 00:19:58 +02:00
|
|
|
<term><replaceable class="parameter">element</replaceable></term>
|
2003-04-22 12:08:08 +02:00
|
|
|
<listitem>
|
|
|
|
<para>
|
2003-05-09 00:19:58 +02:00
|
|
|
The type being created is an array; this specifies the type of
|
|
|
|
the array elements.
|
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
|
|
|
|
<varlistentry>
|
|
|
|
<term><replaceable class="parameter">delimiter</replaceable></term>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
The delimiter character to be used between values in arrays made
|
|
|
|
of this type.
|
2003-04-22 12:08:08 +02:00
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
|
|
</refsect1>
|
|
|
|
|
2001-09-13 21:05:29 +02:00
|
|
|
<refsect1 id="SQL-CREATETYPE-notes">
|
|
|
|
<title>Notes</title>
|
|
|
|
|
2006-01-13 19:06:45 +01:00
|
|
|
<para>
|
|
|
|
Because there are no restrictions on use of a data type once it's been
|
|
|
|
created, creating a base type is tantamount to granting public execute
|
2008-07-31 18:27:16 +02:00
|
|
|
permission on the functions mentioned in the type definition.
|
|
|
|
This is usually
|
2006-01-13 19:06:45 +01:00
|
|
|
not an issue for the sorts of functions that are useful in a type
|
|
|
|
definition. But you might want to think twice before designing a type
|
|
|
|
in a way that would require <quote>secret</> information to be used
|
|
|
|
while converting it to or from external form.
|
|
|
|
</para>
|
|
|
|
|
2007-05-12 02:55:00 +02:00
|
|
|
<para>
|
|
|
|
Before <productname>PostgreSQL</productname> version 8.3, the name of
|
|
|
|
a generated array type was always exactly the element type's name with one
|
|
|
|
underscore character (<literal>_</literal>) prepended. (Type names were
|
|
|
|
therefore restricted in length to one less character than other names.)
|
|
|
|
While this is still usually the case, the array type name may vary from
|
|
|
|
this in case of maximum-length names or collisions with user type names
|
|
|
|
that begin with underscore. Writing code that depends on this convention
|
|
|
|
is therefore deprecated. Instead, use
|
|
|
|
<structname>pg_type</>.<structfield>typarray</> to locate the array type
|
|
|
|
associated with a given type.
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
It may be advisable to avoid using type and table names that begin with
|
|
|
|
underscore. While the server will change generated array type names to
|
|
|
|
avoid collisions with user-given names, there is still risk of confusion,
|
|
|
|
particularly with old client software that may assume that type names
|
|
|
|
beginning with underscores always represent arrays.
|
|
|
|
</para>
|
|
|
|
|
2006-02-28 23:37:27 +01:00
|
|
|
<para>
|
|
|
|
Before <productname>PostgreSQL</productname> version 8.2, the syntax
|
|
|
|
<literal>CREATE TYPE <replaceable>name</></literal> did not exist.
|
|
|
|
The way to create a new base type was to create its input function first.
|
|
|
|
In this approach, <productname>PostgreSQL</productname> will first see
|
|
|
|
the name of the new data type as the return type of the input function.
|
|
|
|
The shell type is implicitly created in this situation, and then it
|
|
|
|
can be referenced in the definitions of the remaining I/O functions.
|
Update reference documentation on may/can/might:
Standard English uses "may", "can", and "might" in different ways:
may - permission, "You may borrow my rake."
can - ability, "I can lift that log."
might - possibility, "It might rain today."
Unfortunately, in conversational English, their use is often mixed, as
in, "You may use this variable to do X", when in fact, "can" is a better
choice. Similarly, "It may crash" is better stated, "It might crash".
2007-02-01 00:26:05 +01:00
|
|
|
This approach still works, but is deprecated and might be disallowed in
|
2006-02-28 23:37:27 +01:00
|
|
|
some future release. Also, to avoid accidentally cluttering
|
|
|
|
the catalogs with shell types as a result of simple typos in function
|
|
|
|
definitions, a shell type will only be made this way when the input
|
|
|
|
function is written in C.
|
|
|
|
</para>
|
|
|
|
|
2003-04-22 12:08:08 +02:00
|
|
|
<para>
|
|
|
|
In <productname>PostgreSQL</productname> versions before 7.3, it
|
2006-02-28 23:37:27 +01:00
|
|
|
was customary to avoid creating a shell type at all, by replacing the
|
2003-04-22 12:08:08 +02:00
|
|
|
functions' forward references to the type name with the placeholder
|
|
|
|
pseudotype <type>opaque</>. The <type>cstring</> arguments and
|
|
|
|
results also had to be declared as <type>opaque</> before 7.3. To
|
|
|
|
support loading of old dump files, <command>CREATE TYPE</> will
|
2006-02-28 23:37:27 +01:00
|
|
|
accept I/O functions declared using <type>opaque</>, but it will issue
|
|
|
|
a notice and change the function declarations to use the correct
|
2003-04-22 12:08:08 +02:00
|
|
|
types.
|
|
|
|
</para>
|
2006-02-28 23:37:27 +01:00
|
|
|
|
2001-09-13 21:05:29 +02:00
|
|
|
</refsect1>
|
2006-12-30 22:21:56 +01:00
|
|
|
|
1998-07-29 08:23:26 +02:00
|
|
|
<refsect1>
|
|
|
|
<title>Examples</title>
|
2003-04-22 12:08:08 +02:00
|
|
|
|
1998-07-29 08:23:26 +02:00
|
|
|
<para>
|
2003-05-09 00:19:58 +02:00
|
|
|
This example creates a composite type and uses it in
|
|
|
|
a function definition:
|
|
|
|
<programlisting>
|
|
|
|
CREATE TYPE compfoo AS (f1 int, f2 text);
|
2005-01-04 01:39:53 +01:00
|
|
|
|
2004-05-17 01:22:08 +02:00
|
|
|
CREATE FUNCTION getfoo() RETURNS SETOF compfoo AS $$
|
|
|
|
SELECT fooid, fooname FROM foo
|
|
|
|
$$ LANGUAGE SQL;
|
2003-05-09 00:19:58 +02:00
|
|
|
</programlisting>
|
|
|
|
</para>
|
|
|
|
|
2007-04-02 05:49:42 +02:00
|
|
|
<para>
|
|
|
|
This example creates an enumerated type and uses it in
|
|
|
|
a table definition:
|
|
|
|
<programlisting>
|
|
|
|
CREATE TYPE bug_status AS ENUM ('new', 'open', 'closed');
|
|
|
|
|
|
|
|
CREATE TABLE bug (
|
2007-10-29 18:29:59 +01:00
|
|
|
id serial,
|
2007-04-02 05:49:42 +02:00
|
|
|
description text,
|
|
|
|
status bug_status
|
|
|
|
);
|
|
|
|
</programlisting>
|
|
|
|
</para>
|
|
|
|
|
2003-05-09 00:19:58 +02:00
|
|
|
<para>
|
|
|
|
This example creates the base data type <type>box</type> and then uses the
|
2001-01-14 00:58:55 +01:00
|
|
|
type in a table definition:
|
2001-09-13 21:05:29 +02:00
|
|
|
<programlisting>
|
2006-02-28 23:37:27 +01:00
|
|
|
CREATE TYPE box;
|
|
|
|
|
|
|
|
CREATE FUNCTION my_box_in_function(cstring) RETURNS box AS ... ;
|
|
|
|
CREATE FUNCTION my_box_out_function(box) RETURNS cstring AS ... ;
|
|
|
|
|
2003-04-22 12:08:08 +02:00
|
|
|
CREATE TYPE box (
|
|
|
|
INTERNALLENGTH = 16,
|
|
|
|
INPUT = my_box_in_function,
|
|
|
|
OUTPUT = my_box_out_function
|
|
|
|
);
|
|
|
|
|
|
|
|
CREATE TABLE myboxes (
|
|
|
|
id integer,
|
|
|
|
description box
|
|
|
|
);
|
2001-09-13 21:05:29 +02:00
|
|
|
</programlisting>
|
1999-07-22 17:09:15 +02:00
|
|
|
</para>
|
|
|
|
|
1998-07-29 08:23:26 +02:00
|
|
|
<para>
|
2003-04-22 12:08:08 +02:00
|
|
|
If the internal structure of <type>box</type> were an array of four
|
2007-02-01 01:28:19 +01:00
|
|
|
<type>float4</> elements, we might instead use:
|
2001-09-13 21:05:29 +02:00
|
|
|
<programlisting>
|
2003-04-22 12:08:08 +02:00
|
|
|
CREATE TYPE box (
|
|
|
|
INTERNALLENGTH = 16,
|
|
|
|
INPUT = my_box_in_function,
|
|
|
|
OUTPUT = my_box_out_function,
|
|
|
|
ELEMENT = float4
|
|
|
|
);
|
2001-09-13 21:05:29 +02:00
|
|
|
</programlisting>
|
2003-04-22 12:08:08 +02:00
|
|
|
which would allow a box value's component numbers to be accessed
|
2001-11-03 22:42:47 +01:00
|
|
|
by subscripting. Otherwise the type behaves the same as before.
|
1999-07-06 19:16:42 +02:00
|
|
|
</para>
|
1999-07-22 17:09:15 +02:00
|
|
|
|
1998-07-29 08:23:26 +02:00
|
|
|
<para>
|
2001-11-03 22:42:47 +01:00
|
|
|
This example creates a large object type and uses it in
|
2001-01-14 00:58:55 +01:00
|
|
|
a table definition:
|
2001-09-13 21:05:29 +02:00
|
|
|
<programlisting>
|
2003-04-22 12:08:08 +02:00
|
|
|
CREATE TYPE bigobj (
|
|
|
|
INPUT = lo_filein, OUTPUT = lo_fileout,
|
|
|
|
INTERNALLENGTH = VARIABLE
|
|
|
|
);
|
|
|
|
CREATE TABLE big_objs (
|
|
|
|
id integer,
|
|
|
|
obj bigobj
|
|
|
|
);
|
2002-08-15 18:36:08 +02:00
|
|
|
</programlisting>
|
|
|
|
</para>
|
|
|
|
|
2003-04-22 12:08:08 +02:00
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|
|
<para>
|
|
|
|
More examples, including suitable input and output functions, are
|
2005-01-04 01:39:53 +01:00
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|
|
in <xref linkend="xtypes">.
|
2003-04-22 12:08:08 +02:00
|
|
|
</para>
|
2001-09-13 21:05:29 +02:00
|
|
|
</refsect1>
|
1998-07-29 08:23:26 +02:00
|
|
|
|
2001-09-13 21:05:29 +02:00
|
|
|
<refsect1 id="SQL-CREATETYPE-compatibility">
|
|
|
|
<title>Compatibility</title>
|
1998-12-29 03:24:47 +01:00
|
|
|
|
2001-09-13 21:05:29 +02:00
|
|
|
<para>
|
|
|
|
This <command>CREATE TYPE</command> command is a
|
|
|
|
<productname>PostgreSQL</productname> extension. There is a
|
2005-11-01 22:09:51 +01:00
|
|
|
<command>CREATE TYPE</command> statement in the <acronym>SQL</> standard
|
|
|
|
that is rather different in detail.
|
2001-09-13 21:05:29 +02:00
|
|
|
</para>
|
1998-07-29 08:23:26 +02:00
|
|
|
</refsect1>
|
|
|
|
|
2001-09-13 21:05:29 +02:00
|
|
|
<refsect1 id="SQL-CREATETYPE-see-also">
|
|
|
|
<title>See Also</title>
|
|
|
|
|
|
|
|
<simplelist type="inline">
|
2002-11-22 00:34:43 +01:00
|
|
|
<member><xref linkend="sql-createfunction" endterm="sql-createfunction-title"></member>
|
|
|
|
<member><xref linkend="sql-droptype" endterm="sql-droptype-title"></member>
|
2004-06-25 23:55:59 +02:00
|
|
|
<member><xref linkend="sql-altertype" endterm="sql-altertype-title"></member>
|
2006-04-06 00:11:58 +02:00
|
|
|
<member><xref linkend="sql-createdomain" endterm="sql-createdomain-title"></member>
|
2001-09-13 21:05:29 +02:00
|
|
|
</simplelist>
|
1998-12-29 03:24:47 +01:00
|
|
|
</refsect1>
|
2001-09-13 21:05:29 +02:00
|
|
|
|
1999-07-06 19:16:42 +02:00
|
|
|
</refentry>
|