diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/ref/create_cast.sgml | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/doc/src/sgml/ref/create_cast.sgml b/doc/src/sgml/ref/create_cast.sgml index 7fd5ba0d470..00a44719662 100644 --- a/doc/src/sgml/ref/create_cast.sgml +++ b/doc/src/sgml/ref/create_cast.sgml @@ -1,4 +1,4 @@ -<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/create_cast.sgml,v 1.2 2002/08/11 17:44:12 petere Exp $ --> +<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/create_cast.sgml,v 1.3 2002/09/01 02:37:02 tgl Exp $ --> <refentry id="SQL-CREATECAST"> <refmeta> @@ -28,8 +28,8 @@ CREATE CAST (<replaceable>sourcetype</replaceable> AS <replaceable>targettype</r <para> <command>CREATE CAST</command> defines a new cast. A cast - specifies which function can be invoked when a conversion between - two data types is requested. For example, + specifies how to perform a conversion between + two data types. For example, <programlisting> SELECT CAST(42 AS text); </programlisting> @@ -49,7 +49,7 @@ SELECT CAST(42 AS text); </para> <para> - A cast can marked <literal>AS ASSIGNMENT</>, which means that it + A cast can be marked <literal>AS ASSIGNMENT</>, which means that it can be invoked implicitly in any context where the conversion it defines is required. Cast functions not so marked can be invoked only by explicit <literal>CAST</>, @@ -72,7 +72,7 @@ INSERT INTO foo(f1) VALUES(42); <productname>PostgreSQL</productname> to choose surprising interpretations of commands, or to be unable to resolve commands at all because there are multiple possible interpretations. A good - rule of thumb is to make cast implicitly invokable only for + rule of thumb is to make a cast implicitly invokable only for information-preserving transformations between types in the same general type category. For example, <type>int2</type> to <type>int4</type> casts can reasonably be implicit, but be wary of @@ -161,9 +161,10 @@ INSERT INTO foo(f1) VALUES(42); <para> Prior to PostgreSQL 7.3, every function that had the same name as a data type, returned that data type, and took one argument of a - different type was automatically a cast function. This system has + different type was automatically a cast function. This convention has been abandoned in face of the introduction of schemas and to be - able to store binary compatible casts. The built-in cast functions + able to represent binary compatible casts in the catalogs. The built-in + cast functions still follow this naming scheme, but they have to be declared as casts explicitly now. </para> @@ -175,7 +176,7 @@ INSERT INTO foo(f1) VALUES(42); <para> To create a cast from type <type>text</type> to type - <type>int</type> using the function <literal>int4(text)</literal>: + <type>int4</type> using the function <literal>int4(text)</literal>: <programlisting> CREATE CAST (text AS int4) WITH FUNCTION int4(text); </programlisting> |