diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/ecpg.sgml | 39 |
1 files changed, 38 insertions, 1 deletions
diff --git a/doc/src/sgml/ecpg.sgml b/doc/src/sgml/ecpg.sgml index 7f8b4dd5c02..29333e37679 100644 --- a/doc/src/sgml/ecpg.sgml +++ b/doc/src/sgml/ecpg.sgml @@ -1483,6 +1483,10 @@ EXEC SQL END DECLARE SECTION; <sect4> <title>Typedefs</title> + <indexterm> + <primary>typedef</primary> + <secondary>in ECPG</secondary> + </indexterm> <para> Use the <literal>typedef</literal> keyword to map new types to already @@ -1497,8 +1501,41 @@ EXEC SQL END DECLARE SECTION; <programlisting> EXEC SQL TYPE serial_t IS long; </programlisting> - This declaration does not need to be part of a declare section. + This declaration does not need to be part of a declare section; + that is, you can also write typedefs as normal C statements. </para> + + <para> + Any word you declare as a typedef cannot be used as a SQL keyword + in <literal>EXEC SQL</literal> commands later in the same program. + For example, this won't work: +<programlisting> +EXEC SQL BEGIN DECLARE SECTION; + typedef int start; +EXEC SQL END DECLARE SECTION; +... +EXEC SQL START TRANSACTION; +</programlisting> + ECPG will report a syntax error for <literal>START + TRANSACTION</literal>, because it no longer + recognizes <literal>START</literal> as a SQL keyword, + only as a typedef. + (If you have such a conflict, and renaming the typedef + seems impractical, you could write the SQL command + using <link linkend="ecpg-dynamic">dynamic SQL</link>.) + </para> + + <note> + <para> + In <productname>PostgreSQL</productname> releases before v16, use + of SQL keywords as typedef names was likely to result in syntax + errors associated with use of the typedef itself, rather than use + of the name as a SQL keyword. The new behavior is less likely to + cause problems when an existing ECPG application is recompiled in + a new <productname>PostgreSQL</productname> release with new + keywords. + </para> + </note> </sect4> <sect4> |