diff options
Diffstat (limited to 'doc/src/sgml')
| -rw-r--r-- | doc/src/sgml/ref/create_type.sgml | 34 |
1 files changed, 33 insertions, 1 deletions
diff --git a/doc/src/sgml/ref/create_type.sgml b/doc/src/sgml/ref/create_type.sgml index 222d41d28bb..78b11b8a80e 100644 --- a/doc/src/sgml/ref/create_type.sgml +++ b/doc/src/sgml/ref/create_type.sgml @@ -1,5 +1,5 @@ <!-- -$PostgreSQL: pgsql/doc/src/sgml/ref/create_type.sgml,v 1.78 2008/11/14 10:22:46 petere Exp $ +$PostgreSQL: pgsql/doc/src/sgml/ref/create_type.sgml,v 1.79 2008/11/30 19:01:29 tgl Exp $ PostgreSQL documentation --> @@ -39,6 +39,7 @@ CREATE TYPE <replaceable class="parameter">name</replaceable> ( [ , PASSEDBYVALUE ] [ , ALIGNMENT = <replaceable class="parameter">alignment</replaceable> ] [ , STORAGE = <replaceable class="parameter">storage</replaceable> ] + [ , LIKE = <replaceable class="parameter">like_type</replaceable> ] [ , CATEGORY = <replaceable class="parameter">category</replaceable> ] [ , PREFERRED = <replaceable class="parameter">preferred</replaceable> ] [ , DEFAULT = <replaceable class="parameter">default</replaceable> ] @@ -291,6 +292,21 @@ CREATE TYPE <replaceable class="parameter">name</replaceable> </para> <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> + + <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 @@ -525,6 +541,22 @@ CREATE TYPE <replaceable class="parameter">name</replaceable> </varlistentry> <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> + + <varlistentry> <term><replaceable class="parameter">category</replaceable></term> <listitem> <para> |