2000-03-31 05:27:42 +02:00
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$Header: /cvsroot/pgsql/doc/src/sgml/xfunc.sgml,v 1.30 2001/01/22 16:11:17 tgl Exp $
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2000-03-31 05:27:42 +02:00
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-->
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1999-07-22 17:11:05 +02:00
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<chapter id="xfunc">
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<title id="xfunc-title">Extending <acronym>SQL</acronym>: Functions</title>
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<para>
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As it turns out, part of defining a new type is the
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definition of functions that describe its behavior.
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Consequently, while it is possible to define a new
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function without defining a new type, the reverse is
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not true. We therefore describe how to add new functions
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to <productname>Postgres</productname> before describing
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how to add new types.
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</para>
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<para>
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<productname>Postgres</productname> <acronym>SQL</acronym>
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provides three types of functions:
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<itemizedlist>
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<listitem>
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<para>
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query language functions
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(functions written in <acronym>SQL</acronym>)
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</para>
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</listitem>
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<listitem>
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<para>
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procedural language
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functions (functions written in, for example, PLTCL or PLSQL)
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</para>
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</listitem>
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<listitem>
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<para>
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programming
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language functions (functions written in a compiled
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programming language such as <acronym>C</acronym>)
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</para>
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</listitem>
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</itemizedlist>
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Every kind
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of function can take a base type, a composite type or
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some combination as arguments (parameters). In addition,
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every kind of function can return a base type or
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a composite type. It's easiest to define <acronym>SQL</acronym>
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functions, so we'll start with those. Examples in this section
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can also be found in <filename>funcs.sql</filename>
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and <filename>funcs.c</filename>.
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</para>
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2000-09-29 22:21:34 +02:00
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<sect1 id="xfunc-sql">
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1999-07-22 17:11:05 +02:00
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<title>Query Language (<acronym>SQL</acronym>) Functions</title>
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<para>
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SQL functions execute an arbitrary list of SQL queries, returning
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the results of the last query in the list. SQL functions in general
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return sets. If their returntype is not specified as a
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<literal>setof</literal>,
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then an arbitrary element of the last query's result will be returned.
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</para>
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<para>
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The body of a SQL function following AS
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2000-08-25 01:36:29 +02:00
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should be a list of queries separated by semicolons and
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bracketed within single-quote marks. Note that quote marks used in
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the queries must be escaped, by preceding them with a backslash.
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1999-07-22 17:11:05 +02:00
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</para>
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<para>
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Arguments to the SQL function may be referenced in the queries using
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a $n syntax: $1 refers to the first argument, $2 to the second, and so
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on. If an argument is complex, then a <firstterm>dot</firstterm>
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notation (e.g. "$1.emp") may be
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used to access attributes of the argument or
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to invoke functions.
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</para>
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<sect2>
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<title>Examples</title>
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<para>
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To illustrate a simple SQL function, consider the following,
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which might be used to debit a bank account:
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<programlisting>
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2000-05-20 13:24:37 +02:00
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CREATE FUNCTION tp1 (int4, float8)
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RETURNS int4
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AS 'UPDATE bank
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SET balance = bank.balance - $2
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WHERE bank.acctountno = $1;
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SELECT 1;'
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2000-05-20 13:24:37 +02:00
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LANGUAGE 'sql';
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1999-07-22 17:11:05 +02:00
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</programlisting>
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A user could execute this function to debit account 17 by $100.00 as
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follows:
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<programlisting>
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SELECT tp1( 17,100.0);
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</programlisting>
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</para>
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<para>
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The following more interesting example takes a single argument of type
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EMP, and retrieves multiple results:
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<programlisting>
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CREATE FUNCTION hobbies (EMP) RETURNS SETOF hobbies
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AS 'SELECT hobbies.* FROM hobbies
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WHERE $1.name = hobbies.person'
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LANGUAGE 'sql';
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1999-07-22 17:11:05 +02:00
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</programlisting>
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</para>
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</sect2>
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<sect2>
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<title><acronym>SQL</acronym> Functions on Base Types</title>
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<para>
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The simplest possible <acronym>SQL</acronym> function has no arguments and
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1999-10-04 17:18:54 +02:00
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simply returns a base type, such as <literal>int4</literal>:
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1998-03-01 09:16:16 +01:00
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1999-07-22 17:11:05 +02:00
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<programlisting>
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2000-05-20 13:24:37 +02:00
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CREATE FUNCTION one()
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RETURNS int4
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AS 'SELECT 1 as RESULT;'
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LANGUAGE 'sql';
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1998-03-01 09:16:16 +01:00
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2000-05-02 22:02:03 +02:00
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SELECT one() AS answer;
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1998-03-01 09:16:16 +01:00
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+-------+
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|answer |
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+-------+
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|1 |
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+-------+
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1999-07-22 17:11:05 +02:00
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</programlisting>
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</para>
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<para>
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2000-08-25 01:36:29 +02:00
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Notice that we defined a column name for the function's result
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(with the name RESULT), but this column name is not visible
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outside the function. Hence, the result is labelled answer
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1998-03-01 09:16:16 +01:00
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instead of one.
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1999-07-22 17:11:05 +02:00
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</para>
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<para>
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It's almost as easy to define <acronym>SQL</acronym> functions
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1999-03-14 16:24:15 +01:00
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that take base types as arguments. In the example below, notice
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how we refer to the arguments within the function as $1
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and $2:
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<programlisting>
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2000-05-20 13:24:37 +02:00
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CREATE FUNCTION add_em(int4, int4)
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RETURNS int4
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AS 'SELECT $1 + $2;'
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LANGUAGE 'sql';
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1998-03-01 09:16:16 +01:00
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2000-05-02 22:02:03 +02:00
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SELECT add_em(1, 2) AS answer;
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1998-03-01 09:16:16 +01:00
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2000-08-25 17:17:50 +02:00
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+-------+
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|answer |
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+-------+
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|3 |
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+-------+
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1999-07-22 17:11:05 +02:00
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</programlisting>
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</para>
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</sect2>
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1998-03-01 09:16:16 +01:00
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1999-07-22 17:11:05 +02:00
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<sect2>
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<title><acronym>SQL</acronym> Functions on Composite Types</title>
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1998-03-01 09:16:16 +01:00
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1999-07-22 17:11:05 +02:00
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<para>
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1998-03-01 09:16:16 +01:00
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When specifying functions with arguments of composite
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types (such as EMP), we must not only specify which
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argument we want (as we did above with $1 and $2) but
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also the attributes of that argument. For example,
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take the function double_salary that computes what your
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1999-07-22 17:11:05 +02:00
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salary would be if it were doubled:
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<programlisting>
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2000-05-20 13:24:37 +02:00
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CREATE FUNCTION double_salary(EMP)
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RETURNS int4
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AS 'SELECT $1.salary * 2 AS salary;'
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LANGUAGE 'sql';
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2000-05-02 22:02:03 +02:00
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SELECT name, double_salary(EMP) AS dream
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FROM EMP
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2001-01-20 21:59:29 +01:00
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WHERE EMP.cubicle ~= point '(2,1)';
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+-----+-------+
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|name | dream |
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+-----+-------+
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|Sam | 2400 |
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+-----+-------+
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1999-07-22 17:11:05 +02:00
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</programlisting>
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</para>
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<para>
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1998-03-01 09:16:16 +01:00
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Notice the use of the syntax $1.salary.
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Before launching into the subject of functions that
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return composite types, we must first introduce the
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function notation for projecting attributes. The simple way
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to explain this is that we can usually use the
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2001-01-14 00:58:55 +01:00
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notations attribute(table) and table.attribute interchangably:
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1999-07-22 17:11:05 +02:00
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<programlisting>
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2000-05-02 22:02:03 +02:00
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--
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-- this is the same as:
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-- SELECT EMP.name AS youngster FROM EMP WHERE EMP.age < 30
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--
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SELECT name(EMP) AS youngster
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FROM EMP
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WHERE age(EMP) < 30;
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2000-08-25 17:17:50 +02:00
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+----------+
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|youngster |
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+----------+
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|Sam |
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+----------+
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1999-07-22 17:11:05 +02:00
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</programlisting>
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</para>
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<para>
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1998-03-01 09:16:16 +01:00
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As we shall see, however, this is not always the case.
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This function notation is important when we want to use
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2001-01-14 00:58:55 +01:00
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a function that returns a single row. We do this
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by assembling the entire row within the function,
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1998-03-01 09:16:16 +01:00
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attribute by attribute. This is an example of a function
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2001-01-14 00:58:55 +01:00
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that returns a single EMP row:
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1999-07-22 17:11:05 +02:00
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<programlisting>
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2000-05-20 13:24:37 +02:00
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CREATE FUNCTION new_emp()
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RETURNS EMP
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2001-01-20 21:59:29 +01:00
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AS 'SELECT text ''None'' AS name,
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1000 AS salary,
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25 AS age,
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2001-01-20 21:59:29 +01:00
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point ''(2,2)'' AS cubicle'
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2000-08-25 17:17:50 +02:00
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LANGUAGE 'sql';
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1999-07-22 17:11:05 +02:00
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</programlisting>
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</para>
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<para>
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1998-03-01 09:16:16 +01:00
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In this case we have specified each of the attributes
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with a constant value, but any computation or expression
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could have been substituted for these constants.
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Defining a function like this can be tricky. Some of
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the more important caveats are as follows:
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1999-07-22 17:11:05 +02:00
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<itemizedlist>
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<listitem>
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<para>
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The target list order must be exactly the same as
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that in which the attributes appear in the CREATE
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2000-08-25 01:36:29 +02:00
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TABLE statement that defined the composite type.
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1999-07-22 17:11:05 +02:00
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</para>
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</listitem>
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<listitem>
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<para>
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2001-01-20 21:59:29 +01:00
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You must typecast the expressions to match the
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2000-08-25 01:36:29 +02:00
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composite type's definition, or you will get errors like this:
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1999-07-22 17:11:05 +02:00
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<programlisting>
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<computeroutput>
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2000-08-25 01:36:29 +02:00
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ERROR: function declared to return emp returns varchar instead of text at column 1
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1999-07-22 17:11:05 +02:00
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</computeroutput>
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</programlisting>
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</para>
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</listitem>
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<listitem>
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<para>
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2001-01-14 00:58:55 +01:00
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When calling a function that returns a row, we
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cannot retrieve the entire row. We must either
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project an attribute out of the row or pass the
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entire row into another function.
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1999-07-22 17:11:05 +02:00
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<programlisting>
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2000-05-02 22:02:03 +02:00
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SELECT name(new_emp()) AS nobody;
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1998-03-01 09:16:16 +01:00
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2000-08-25 17:17:50 +02:00
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+-------+
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|nobody |
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+-------+
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|None |
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+-------+
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1999-07-22 17:11:05 +02:00
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</programlisting>
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</para>
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</listitem>
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<listitem>
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<para>
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The reason why, in general, we must use the function
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1998-03-01 09:16:16 +01:00
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syntax for projecting attributes of function return
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values is that the parser just doesn't understand
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the other (dot) syntax for projection when combined
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with function calls.
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1999-07-22 17:11:05 +02:00
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<programlisting>
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2000-05-02 22:02:03 +02:00
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SELECT new_emp().name AS nobody;
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2000-05-18 16:24:38 +02:00
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NOTICE:parser: syntax error at or near "."
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1999-07-22 17:11:05 +02:00
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</programlisting>
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</para>
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</listitem>
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</itemizedlist>
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</para>
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<para>
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Any collection of commands in the <acronym>SQL</acronym> query
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1999-03-14 16:24:15 +01:00
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language can be packaged together and defined as a function.
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1999-10-04 17:18:54 +02:00
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The commands can include updates (i.e.,
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<command>INSERT</command>, <command>UPDATE</command>, and
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<command>DELETE</command>) as well
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as <command>SELECT</command> queries. However, the final command
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must be a <command>SELECT</command> that returns whatever is
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1998-03-01 09:16:16 +01:00
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specified as the function's returntype.
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1999-07-22 17:11:05 +02:00
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<programlisting>
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2000-05-20 13:24:37 +02:00
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CREATE FUNCTION clean_EMP ()
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2000-08-25 17:17:50 +02:00
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RETURNS int4
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AS 'DELETE FROM EMP
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WHERE EMP.salary <= 0;
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SELECT 1 AS ignore_this;'
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LANGUAGE 'sql';
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2000-05-02 22:02:03 +02:00
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SELECT clean_EMP();
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2000-08-25 17:17:50 +02:00
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+--+
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|x |
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+--+
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|1 |
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+--+
|
1999-07-22 17:11:05 +02:00
|
|
|
</programlisting>
|
|
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
</sect1>
|
|
|
|
|
2000-09-29 22:21:34 +02:00
|
|
|
<sect1 id="xfunc-pl">
|
1999-07-22 17:11:05 +02:00
|
|
|
<title>Procedural Language Functions</title>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
Procedural languages aren't built into Postgres. They are offered
|
|
|
|
by loadable modules. Please refer to the documentation for the
|
|
|
|
PL in question for details about the syntax and how the AS
|
|
|
|
clause is interpreted by the PL handler.
|
|
|
|
</para>
|
1998-03-01 09:16:16 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<para>
|
2000-11-20 21:36:57 +01:00
|
|
|
There are currently three procedural languages available in the standard
|
|
|
|
<productname>Postgres</productname> distribution (PLSQL, PLTCL and
|
|
|
|
PLPERL), and other languages can be defined.
|
2000-12-26 01:10:37 +01:00
|
|
|
Refer to <xref linkend="xplang"> for
|
1999-07-22 17:11:05 +02:00
|
|
|
more information.
|
|
|
|
</para>
|
|
|
|
</sect1>
|
1998-03-01 09:16:16 +01:00
|
|
|
|
2000-09-29 22:21:34 +02:00
|
|
|
<sect1 id="xfunc-internal">
|
1999-07-22 17:11:05 +02:00
|
|
|
<title>Internal Functions</title>
|
1998-03-01 09:16:16 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<para>
|
2000-12-22 19:57:50 +01:00
|
|
|
Internal functions are functions written in C that have been statically
|
1999-07-22 17:11:05 +02:00
|
|
|
linked into the <productname>Postgres</productname> backend
|
|
|
|
process. The AS
|
|
|
|
clause gives the C-language name of the function, which need not be the
|
|
|
|
same as the name being declared for SQL use.
|
|
|
|
(For reasons of backwards compatibility, an empty AS
|
|
|
|
string is accepted as meaning that the C-language function name is the
|
|
|
|
same as the SQL name.) Normally, all internal functions present in the
|
|
|
|
backend are declared as SQL functions during database initialization,
|
|
|
|
but a user could use <command>CREATE FUNCTION</command>
|
|
|
|
to create additional alias names for an internal function.
|
|
|
|
</para>
|
2000-08-25 01:36:29 +02:00
|
|
|
|
|
|
|
<para>
|
|
|
|
Internal functions are declared in <command>CREATE FUNCTION</command>
|
2000-11-20 21:36:57 +01:00
|
|
|
with language name <literal>internal</literal>.
|
2000-08-25 01:36:29 +02:00
|
|
|
</para>
|
1999-07-22 17:11:05 +02:00
|
|
|
</sect1>
|
|
|
|
|
2000-09-29 22:21:34 +02:00
|
|
|
<sect1 id="xfunc-c">
|
1999-07-22 17:11:05 +02:00
|
|
|
<title>Compiled (C) Language Functions</title>
|
|
|
|
|
|
|
|
<para>
|
I have been working with user defined types and user defined c
functions. One problem that I have encountered with the function
manager is that it does not allow the user to define type conversion
functions that convert between user types. For instance if mytype1,
mytype2, and mytype3 are three Postgresql user types, and if I wish to
define Postgresql conversion functions like
I run into problems, because the Postgresql dynamic loader would look
for a single link symbol, mytype3, for both pieces of object code. If
I just change the name of one of the Postgresql functions (to make the
symbols distinct), the automatic type conversion that Postgresql uses,
for example, when matching operators to arguments no longer finds the
type conversion function.
The solution that I propose, and have implemented in the attatched
patch extends the CREATE FUNCTION syntax as follows. In the first case
above I use the link symbol mytype2_to_mytype3 for the link object
that implements the first conversion function, and define the
Postgresql operator with the following syntax
The patch includes changes to the parser to include the altered
syntax, changes to the ProcedureStmt node in nodes/parsenodes.h,
changes to commands/define.c to handle the extra information in the AS
clause, and changes to utils/fmgr/dfmgr.c that alter the way that the
dynamic loader figures out what link symbol to use. I store the
string for the link symbol in the prosrc text attribute of the pg_proc
table which is currently unused in rows that reference dynamically
loaded
functions.
Bernie Frankpitt
1999-09-28 06:34:56 +02:00
|
|
|
Functions written in C can be compiled into dynamically loadable
|
2000-08-25 01:36:29 +02:00
|
|
|
objects (also called shared libraries), and used to implement user-defined
|
|
|
|
SQL functions. The first time a user-defined function in a particular
|
|
|
|
loadable object file is called in a backend session,
|
|
|
|
the dynamic loader loads that object file into memory so that the
|
|
|
|
function can be called. The <command>CREATE FUNCTION</command>
|
|
|
|
for a user-defined function must therefore specify two pieces of
|
|
|
|
information for the function: the name of the loadable
|
|
|
|
object file, and the C name (link symbol) of the specific function to call
|
|
|
|
within that object file. If the C name is not explicitly specified then
|
|
|
|
it is assumed to be the same as the SQL function name.
|
I have been working with user defined types and user defined c
functions. One problem that I have encountered with the function
manager is that it does not allow the user to define type conversion
functions that convert between user types. For instance if mytype1,
mytype2, and mytype3 are three Postgresql user types, and if I wish to
define Postgresql conversion functions like
I run into problems, because the Postgresql dynamic loader would look
for a single link symbol, mytype3, for both pieces of object code. If
I just change the name of one of the Postgresql functions (to make the
symbols distinct), the automatic type conversion that Postgresql uses,
for example, when matching operators to arguments no longer finds the
type conversion function.
The solution that I propose, and have implemented in the attatched
patch extends the CREATE FUNCTION syntax as follows. In the first case
above I use the link symbol mytype2_to_mytype3 for the link object
that implements the first conversion function, and define the
Postgresql operator with the following syntax
The patch includes changes to the parser to include the altered
syntax, changes to the ProcedureStmt node in nodes/parsenodes.h,
changes to commands/define.c to handle the extra information in the AS
clause, and changes to utils/fmgr/dfmgr.c that alter the way that the
dynamic loader figures out what link symbol to use. I store the
string for the link symbol in the prosrc text attribute of the pg_proc
table which is currently unused in rows that reference dynamically
loaded
functions.
Bernie Frankpitt
1999-09-28 06:34:56 +02:00
|
|
|
|
1999-10-01 17:20:06 +02:00
|
|
|
<note>
|
|
|
|
<para>
|
2000-08-25 01:36:29 +02:00
|
|
|
After it is used for the first time, a dynamically loaded user
|
1999-10-01 17:20:06 +02:00
|
|
|
function is retained in memory, and future calls to the function
|
2000-08-25 01:36:29 +02:00
|
|
|
in the same session will only incur the small overhead of a symbol table
|
|
|
|
lookup.
|
1999-10-01 17:20:06 +02:00
|
|
|
</para>
|
|
|
|
</note>
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
2000-12-22 19:57:50 +01:00
|
|
|
The string that specifies the object file (the first string in the AS
|
I have been working with user defined types and user defined c
functions. One problem that I have encountered with the function
manager is that it does not allow the user to define type conversion
functions that convert between user types. For instance if mytype1,
mytype2, and mytype3 are three Postgresql user types, and if I wish to
define Postgresql conversion functions like
I run into problems, because the Postgresql dynamic loader would look
for a single link symbol, mytype3, for both pieces of object code. If
I just change the name of one of the Postgresql functions (to make the
symbols distinct), the automatic type conversion that Postgresql uses,
for example, when matching operators to arguments no longer finds the
type conversion function.
The solution that I propose, and have implemented in the attatched
patch extends the CREATE FUNCTION syntax as follows. In the first case
above I use the link symbol mytype2_to_mytype3 for the link object
that implements the first conversion function, and define the
Postgresql operator with the following syntax
The patch includes changes to the parser to include the altered
syntax, changes to the ProcedureStmt node in nodes/parsenodes.h,
changes to commands/define.c to handle the extra information in the AS
clause, and changes to utils/fmgr/dfmgr.c that alter the way that the
dynamic loader figures out what link symbol to use. I store the
string for the link symbol in the prosrc text attribute of the pg_proc
table which is currently unused in rows that reference dynamically
loaded
functions.
Bernie Frankpitt
1999-09-28 06:34:56 +02:00
|
|
|
clause) should be the <emphasis>full path</emphasis> of the object
|
2000-11-20 21:36:57 +01:00
|
|
|
code file for the function, bracketed by single quote marks. If a
|
2000-08-25 01:36:29 +02:00
|
|
|
link symbol is given in the AS clause, the link symbol should also be
|
2000-11-20 21:36:57 +01:00
|
|
|
bracketed by single quote marks, and should be exactly the
|
1999-10-04 17:18:54 +02:00
|
|
|
same as the name of the function in the C source code. On Unix systems
|
I have been working with user defined types and user defined c
functions. One problem that I have encountered with the function
manager is that it does not allow the user to define type conversion
functions that convert between user types. For instance if mytype1,
mytype2, and mytype3 are three Postgresql user types, and if I wish to
define Postgresql conversion functions like
I run into problems, because the Postgresql dynamic loader would look
for a single link symbol, mytype3, for both pieces of object code. If
I just change the name of one of the Postgresql functions (to make the
symbols distinct), the automatic type conversion that Postgresql uses,
for example, when matching operators to arguments no longer finds the
type conversion function.
The solution that I propose, and have implemented in the attatched
patch extends the CREATE FUNCTION syntax as follows. In the first case
above I use the link symbol mytype2_to_mytype3 for the link object
that implements the first conversion function, and define the
Postgresql operator with the following syntax
The patch includes changes to the parser to include the altered
syntax, changes to the ProcedureStmt node in nodes/parsenodes.h,
changes to commands/define.c to handle the extra information in the AS
clause, and changes to utils/fmgr/dfmgr.c that alter the way that the
dynamic loader figures out what link symbol to use. I store the
string for the link symbol in the prosrc text attribute of the pg_proc
table which is currently unused in rows that reference dynamically
loaded
functions.
Bernie Frankpitt
1999-09-28 06:34:56 +02:00
|
|
|
the command <command>nm</command> will print all of the link
|
|
|
|
symbols in a dynamically loadable object.
|
2000-08-25 01:36:29 +02:00
|
|
|
|
|
|
|
<note>
|
|
|
|
<para>
|
|
|
|
<productname>Postgres</productname> will not compile a function
|
|
|
|
automatically; it must be compiled before it is used in a CREATE
|
|
|
|
FUNCTION command. See below for additional information.
|
|
|
|
</para>
|
|
|
|
</note>
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
Two different calling conventions are currently used for C functions.
|
2000-11-20 21:36:57 +01:00
|
|
|
The newer "version 1" calling convention is indicated by writing
|
|
|
|
a <literal>PG_FUNCTION_INFO_V1()</literal> macro call for the function,
|
|
|
|
as illustrated below. Lack of such a macro indicates an old-style
|
|
|
|
("version 0") function. The language name specified in CREATE FUNCTION
|
|
|
|
is 'C' in either case. Old-style functions are now deprecated
|
2000-08-25 01:36:29 +02:00
|
|
|
because of portability problems and lack of functionality, but they
|
|
|
|
are still supported for compatibility reasons.
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
|
|
|
|
|
|
|
<sect2>
|
2000-08-25 01:36:29 +02:00
|
|
|
<title>Base Types in C-Language Functions</title>
|
1999-07-22 17:11:05 +02:00
|
|
|
|
|
|
|
<para>
|
|
|
|
The following table gives the C type required for parameters in the C
|
|
|
|
functions that will be loaded into Postgres. The "Defined In"
|
|
|
|
column gives the actual header file (in the
|
|
|
|
<filename>.../src/backend/</filename>
|
|
|
|
directory) that the equivalent C type is defined. However, if you
|
|
|
|
include <filename>utils/builtins.h</filename>,
|
|
|
|
these files will automatically be
|
|
|
|
included.
|
|
|
|
|
|
|
|
<table tocentry="1">
|
|
|
|
<title>Equivalent C Types
|
|
|
|
for Built-In <productname>Postgres</productname> Types</title>
|
|
|
|
<titleabbrev>Equivalent C Types</titleabbrev>
|
|
|
|
<tgroup cols="3">
|
|
|
|
<thead>
|
|
|
|
<row>
|
|
|
|
<entry>
|
|
|
|
Built-In Type
|
|
|
|
</entry>
|
|
|
|
<entry>
|
|
|
|
C Type
|
|
|
|
</entry>
|
|
|
|
<entry>
|
|
|
|
Defined In
|
|
|
|
</entry>
|
|
|
|
</row>
|
|
|
|
</thead>
|
|
|
|
<tbody>
|
|
|
|
<row>
|
|
|
|
<entry>abstime</entry>
|
|
|
|
<entry>AbsoluteTime</entry>
|
|
|
|
<entry>utils/nabstime.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>bool</entry>
|
|
|
|
<entry>bool</entry>
|
|
|
|
<entry>include/c.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>box</entry>
|
|
|
|
<entry>(BOX *)</entry>
|
|
|
|
<entry>utils/geo-decls.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>bytea</entry>
|
|
|
|
<entry>(bytea *)</entry>
|
|
|
|
<entry>include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
2000-11-20 21:36:57 +01:00
|
|
|
<entry>"char"</entry>
|
1999-07-22 17:11:05 +02:00
|
|
|
<entry>char</entry>
|
|
|
|
<entry>N/A</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>cid</entry>
|
|
|
|
<entry>CID</entry>
|
|
|
|
<entry>include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>datetime</entry>
|
|
|
|
<entry>(DateTime *)</entry>
|
|
|
|
<entry>include/c.h or include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>int2</entry>
|
2000-08-25 01:36:29 +02:00
|
|
|
<entry>int2 or int16</entry>
|
1999-07-22 17:11:05 +02:00
|
|
|
<entry>include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
2000-01-11 02:40:04 +01:00
|
|
|
<entry>int2vector</entry>
|
|
|
|
<entry>(int2vector *)</entry>
|
1999-07-22 17:11:05 +02:00
|
|
|
<entry>include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>int4</entry>
|
2000-08-25 01:36:29 +02:00
|
|
|
<entry>int4 or int32</entry>
|
1999-07-22 17:11:05 +02:00
|
|
|
<entry>include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>float4</entry>
|
2000-08-21 19:22:36 +02:00
|
|
|
<entry>(float4 *)</entry>
|
1999-07-22 17:11:05 +02:00
|
|
|
<entry>include/c.h or include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>float8</entry>
|
2000-08-21 19:22:36 +02:00
|
|
|
<entry>(float8 *)</entry>
|
1999-07-22 17:11:05 +02:00
|
|
|
<entry>include/c.h or include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>lseg</entry>
|
|
|
|
<entry>(LSEG *)</entry>
|
|
|
|
<entry>include/geo-decls.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>name</entry>
|
|
|
|
<entry>(Name)</entry>
|
|
|
|
<entry>include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>oid</entry>
|
|
|
|
<entry>oid</entry>
|
|
|
|
<entry>include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
2000-01-11 02:40:04 +01:00
|
|
|
<entry>oidvector</entry>
|
|
|
|
<entry>(oidvector *)</entry>
|
1999-07-22 17:11:05 +02:00
|
|
|
<entry>include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>path</entry>
|
|
|
|
<entry>(PATH *)</entry>
|
|
|
|
<entry>utils/geo-decls.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>point</entry>
|
|
|
|
<entry>(POINT *)</entry>
|
|
|
|
<entry>utils/geo-decls.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>regproc</entry>
|
|
|
|
<entry>regproc or REGPROC</entry>
|
|
|
|
<entry>include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>reltime</entry>
|
|
|
|
<entry>RelativeTime</entry>
|
|
|
|
<entry>utils/nabstime.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>text</entry>
|
|
|
|
<entry>(text *)</entry>
|
|
|
|
<entry>include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>tid</entry>
|
|
|
|
<entry>ItemPointer</entry>
|
|
|
|
<entry>storage/itemptr.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>timespan</entry>
|
|
|
|
<entry>(TimeSpan *)</entry>
|
|
|
|
<entry>include/c.h or include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>tinterval</entry>
|
|
|
|
<entry>TimeInterval</entry>
|
|
|
|
<entry>utils/nabstime.h</entry>
|
|
|
|
</row>
|
|
|
|
<row>
|
|
|
|
<entry>xid</entry>
|
|
|
|
<entry>(XID *)</entry>
|
|
|
|
<entry>include/postgres.h</entry>
|
|
|
|
</row>
|
|
|
|
</tbody>
|
|
|
|
</tgroup>
|
|
|
|
</table>
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
Internally, <productname>Postgres</productname> regards a
|
1999-03-14 16:24:15 +01:00
|
|
|
base type as a "blob of memory." The user-defined
|
|
|
|
functions that you define over a type in turn define the
|
1999-07-22 17:11:05 +02:00
|
|
|
way that <productname>Postgres</productname> can operate
|
|
|
|
on it. That is, <productname>Postgres</productname> will
|
1999-03-14 16:24:15 +01:00
|
|
|
only store and retrieve the data from disk and use your
|
|
|
|
user-defined functions to input, process, and output the data.
|
1998-03-01 09:16:16 +01:00
|
|
|
Base types can have one of three internal formats:
|
1999-07-22 17:11:05 +02:00
|
|
|
|
|
|
|
<itemizedlist>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
pass by value, fixed-length
|
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
pass by reference, fixed-length
|
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
pass by reference, variable-length
|
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</itemizedlist>
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
1998-03-01 09:16:16 +01:00
|
|
|
By-value types can only be 1, 2 or 4 bytes in length
|
|
|
|
(even if your computer supports by-value types of other
|
1999-07-22 17:11:05 +02:00
|
|
|
sizes). <productname>Postgres</productname> itself
|
1999-03-14 16:24:15 +01:00
|
|
|
only passes integer types by value. You should be careful
|
|
|
|
to define your types such that they will be the same
|
|
|
|
size (in bytes) on all architectures. For example, the
|
1999-10-04 17:18:54 +02:00
|
|
|
<literal>long</literal> type is dangerous because it
|
1999-03-14 16:24:15 +01:00
|
|
|
is 4 bytes on some machines and 8 bytes on others, whereas
|
1999-10-04 17:18:54 +02:00
|
|
|
<literal>int</literal> type is 4 bytes on most
|
|
|
|
Unix machines (though not on most
|
1999-03-14 16:24:15 +01:00
|
|
|
personal computers). A reasonable implementation of
|
1999-10-04 17:18:54 +02:00
|
|
|
the <literal>int4</literal> type on Unix
|
1998-03-01 09:16:16 +01:00
|
|
|
machines might be:
|
|
|
|
|
2001-01-12 23:15:32 +01:00
|
|
|
<programlisting>
|
1999-07-22 17:11:05 +02:00
|
|
|
/* 4-byte integer, passed by value */
|
|
|
|
typedef int int4;
|
2001-01-12 23:15:32 +01:00
|
|
|
</programlisting>
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
1998-03-01 09:16:16 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<para>
|
1998-03-01 09:16:16 +01:00
|
|
|
On the other hand, fixed-length types of any size may
|
|
|
|
be passed by-reference. For example, here is a sample
|
1999-07-22 17:11:05 +02:00
|
|
|
implementation of a <productname>Postgres</productname> type:
|
1998-03-01 09:16:16 +01:00
|
|
|
|
2001-01-12 23:15:32 +01:00
|
|
|
<programlisting>
|
1999-07-22 17:11:05 +02:00
|
|
|
/* 16-byte structure, passed by reference */
|
|
|
|
typedef struct
|
|
|
|
{
|
|
|
|
double x, y;
|
|
|
|
} Point;
|
2001-01-12 23:15:32 +01:00
|
|
|
</programlisting>
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
1998-03-01 09:16:16 +01:00
|
|
|
Only pointers to such types can be used when passing
|
1999-07-22 17:11:05 +02:00
|
|
|
them in and out of <productname>Postgres</productname> functions.
|
2000-08-25 01:36:29 +02:00
|
|
|
To return a value of such a type, allocate the right amount of
|
|
|
|
memory with <literal>palloc()</literal>, fill in the allocated memory,
|
|
|
|
and return a pointer to it.
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
1998-03-01 09:16:16 +01:00
|
|
|
Finally, all variable-length types must also be passed
|
|
|
|
by reference. All variable-length types must begin
|
|
|
|
with a length field of exactly 4 bytes, and all data to
|
|
|
|
be stored within that type must be located in the memory
|
|
|
|
immediately following that length field. The
|
|
|
|
length field is the total length of the structure
|
|
|
|
(i.e., it includes the size of the length field
|
|
|
|
itself). We can define the text type as follows:
|
1999-07-22 17:11:05 +02:00
|
|
|
|
2001-01-12 23:15:32 +01:00
|
|
|
<programlisting>
|
1999-07-22 17:11:05 +02:00
|
|
|
typedef struct {
|
|
|
|
int4 length;
|
|
|
|
char data[1];
|
|
|
|
} text;
|
2001-01-12 23:15:32 +01:00
|
|
|
</programlisting>
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
2000-11-20 21:36:57 +01:00
|
|
|
Obviously, the data field shown here is not long enough to hold
|
1999-07-22 17:11:05 +02:00
|
|
|
all possible strings; it's impossible to declare such
|
|
|
|
a structure in <acronym>C</acronym>. When manipulating
|
1999-03-14 16:24:15 +01:00
|
|
|
variable-length types, we must be careful to allocate
|
|
|
|
the correct amount of memory and initialize the length field.
|
|
|
|
For example, if we wanted to store 40 bytes in a text
|
1998-03-01 09:16:16 +01:00
|
|
|
structure, we might use a code fragment like this:
|
|
|
|
|
2001-01-12 23:15:32 +01:00
|
|
|
<programlisting>
|
1999-07-22 17:11:05 +02:00
|
|
|
#include "postgres.h"
|
|
|
|
...
|
|
|
|
char buffer[40]; /* our source data */
|
|
|
|
...
|
|
|
|
text *destination = (text *) palloc(VARHDRSZ + 40);
|
|
|
|
destination->length = VARHDRSZ + 40;
|
|
|
|
memmove(destination->data, buffer, 40);
|
|
|
|
...
|
2001-01-12 23:15:32 +01:00
|
|
|
</programlisting>
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
1998-03-01 09:16:16 +01:00
|
|
|
Now that we've gone over all of the possible structures
|
2000-08-25 01:36:29 +02:00
|
|
|
for base types, we can show some examples of real functions.
|
|
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
|
|
|
|
<sect2>
|
2000-11-20 21:36:57 +01:00
|
|
|
<title>Version-0 Calling Conventions for C-Language Functions</title>
|
2000-08-25 01:36:29 +02:00
|
|
|
|
|
|
|
<para>
|
2001-01-12 23:15:32 +01:00
|
|
|
We present the <quote>old style</quote> calling convention first --- although
|
2000-08-25 01:36:29 +02:00
|
|
|
this approach is now deprecated, it's easier to get a handle on
|
2000-11-20 21:36:57 +01:00
|
|
|
initially. In the version-0 method, the arguments and result
|
2000-08-25 01:36:29 +02:00
|
|
|
of the C function are just declared in normal C style, but being
|
|
|
|
careful to use the C representation of each SQL data type as shown
|
|
|
|
above.
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
Here are some examples:
|
1999-07-22 17:11:05 +02:00
|
|
|
|
2001-01-12 23:15:32 +01:00
|
|
|
<programlisting>
|
2000-05-02 22:02:03 +02:00
|
|
|
#include <string.h>
|
|
|
|
#include "postgres.h"
|
1999-03-14 16:24:15 +01:00
|
|
|
|
2000-05-02 22:02:03 +02:00
|
|
|
/* By Value */
|
1999-03-14 16:24:15 +01:00
|
|
|
|
2000-05-02 22:02:03 +02:00
|
|
|
int
|
|
|
|
add_one(int arg)
|
|
|
|
{
|
2000-08-25 01:36:29 +02:00
|
|
|
return arg + 1;
|
2000-05-02 22:02:03 +02:00
|
|
|
}
|
|
|
|
|
|
|
|
/* By Reference, Fixed Length */
|
|
|
|
|
2000-08-25 01:36:29 +02:00
|
|
|
float8 *
|
|
|
|
add_one_float8(float8 *arg)
|
|
|
|
{
|
|
|
|
float8 *result = (float8 *) palloc(sizeof(float8));
|
|
|
|
|
|
|
|
*result = *arg + 1.0;
|
|
|
|
|
|
|
|
return result;
|
|
|
|
}
|
|
|
|
|
2000-05-02 22:02:03 +02:00
|
|
|
Point *
|
2000-08-25 01:36:29 +02:00
|
|
|
makepoint(Point *pointx, Point *pointy)
|
2000-05-02 22:02:03 +02:00
|
|
|
{
|
|
|
|
Point *new_point = (Point *) palloc(sizeof(Point));
|
|
|
|
|
|
|
|
new_point->x = pointx->x;
|
|
|
|
new_point->y = pointy->y;
|
|
|
|
|
|
|
|
return new_point;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* By Reference, Variable Length */
|
|
|
|
|
|
|
|
text *
|
|
|
|
copytext(text *t)
|
|
|
|
{
|
|
|
|
/*
|
|
|
|
* VARSIZE is the total size of the struct in bytes.
|
|
|
|
*/
|
|
|
|
text *new_t = (text *) palloc(VARSIZE(t));
|
2000-08-25 01:36:29 +02:00
|
|
|
VARATT_SIZEP(new_t) = VARSIZE(t);
|
2000-05-02 22:02:03 +02:00
|
|
|
/*
|
|
|
|
* VARDATA is a pointer to the data region of the struct.
|
|
|
|
*/
|
|
|
|
memcpy((void *) VARDATA(new_t), /* destination */
|
|
|
|
(void *) VARDATA(t), /* source */
|
2000-08-25 01:36:29 +02:00
|
|
|
VARSIZE(t)-VARHDRSZ); /* how many bytes */
|
|
|
|
return new_t;
|
2000-05-02 22:02:03 +02:00
|
|
|
}
|
|
|
|
|
|
|
|
text *
|
|
|
|
concat_text(text *arg1, text *arg2)
|
|
|
|
{
|
|
|
|
int32 new_text_size = VARSIZE(arg1) + VARSIZE(arg2) - VARHDRSZ;
|
|
|
|
text *new_text = (text *) palloc(new_text_size);
|
|
|
|
|
|
|
|
memset((void *) new_text, 0, new_text_size);
|
2000-08-25 01:36:29 +02:00
|
|
|
VARATT_SIZEP(new_text) = new_text_size;
|
2000-05-02 22:02:03 +02:00
|
|
|
strncpy(VARDATA(new_text), VARDATA(arg1), VARSIZE(arg1)-VARHDRSZ);
|
|
|
|
strncat(VARDATA(new_text), VARDATA(arg2), VARSIZE(arg2)-VARHDRSZ);
|
2000-08-25 01:36:29 +02:00
|
|
|
return new_text;
|
2000-05-02 22:02:03 +02:00
|
|
|
}
|
2001-01-12 23:15:32 +01:00
|
|
|
</programlisting>
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
1998-03-01 09:16:16 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<para>
|
2000-08-25 01:36:29 +02:00
|
|
|
Supposing that the above code has been prepared in file
|
|
|
|
<filename>funcs.c</filename> and compiled into a shared object,
|
|
|
|
we could define the functions to <productname>Postgres</productname>
|
|
|
|
with commands like this:
|
1998-03-01 09:16:16 +01:00
|
|
|
|
2001-01-12 23:15:32 +01:00
|
|
|
<programlisting>
|
2000-05-02 22:02:03 +02:00
|
|
|
CREATE FUNCTION add_one(int4) RETURNS int4
|
2000-08-25 01:36:29 +02:00
|
|
|
AS '<replaceable>PGROOT</replaceable>/tutorial/funcs.so' LANGUAGE 'c'
|
|
|
|
WITH (isStrict);
|
2000-05-02 22:02:03 +02:00
|
|
|
|
2000-08-25 01:36:29 +02:00
|
|
|
-- note overloading of SQL function name add_one()
|
|
|
|
CREATE FUNCTION add_one(float8) RETURNS float8
|
|
|
|
AS '<replaceable>PGROOT</replaceable>/tutorial/funcs.so',
|
|
|
|
'add_one_float8'
|
|
|
|
LANGUAGE 'c' WITH (isStrict);
|
2000-05-02 22:02:03 +02:00
|
|
|
|
2000-08-25 01:36:29 +02:00
|
|
|
CREATE FUNCTION makepoint(point, point) RETURNS point
|
|
|
|
AS '<replaceable>PGROOT</replaceable>/tutorial/funcs.so' LANGUAGE 'c'
|
|
|
|
WITH (isStrict);
|
2000-05-02 22:02:03 +02:00
|
|
|
|
|
|
|
CREATE FUNCTION copytext(text) RETURNS text
|
2000-08-25 01:36:29 +02:00
|
|
|
AS '<replaceable>PGROOT</replaceable>/tutorial/funcs.so' LANGUAGE 'c'
|
|
|
|
WITH (isStrict);
|
|
|
|
|
|
|
|
CREATE FUNCTION concat_text(text, text) RETURNS text
|
|
|
|
AS '<replaceable>PGROOT</replaceable>/tutorial/funcs.so' LANGUAGE 'c'
|
|
|
|
WITH (isStrict);
|
2001-01-12 23:15:32 +01:00
|
|
|
</programlisting>
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
1998-03-01 09:16:16 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<para>
|
2000-08-25 01:36:29 +02:00
|
|
|
Here <replaceable>PGROOT</replaceable> stands for the full path to
|
|
|
|
the <productname>Postgres</productname> source tree. Note that
|
|
|
|
depending on your system, the filename for a shared object might
|
|
|
|
not end in <literal>.so</literal>, but in <literal>.sl</literal>
|
|
|
|
or something else; adapt accordingly.
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
Notice that we have specified the functions as "strict", meaning that
|
|
|
|
the system should automatically assume a NULL result if any input
|
|
|
|
value is NULL. By doing this, we avoid having to check for NULL inputs
|
|
|
|
in the function code. Without this, we'd have to check for NULLs
|
|
|
|
explicitly, for example by checking for a null pointer for each
|
|
|
|
pass-by-reference argument. (For pass-by-value arguments, we don't
|
|
|
|
even have a way to check!)
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
2000-11-20 21:36:57 +01:00
|
|
|
Although this calling convention is simple to use,
|
2000-08-25 01:36:29 +02:00
|
|
|
it is not very portable; on some architectures there are problems
|
|
|
|
with passing smaller-than-int data types this way. Also, there is
|
|
|
|
no simple way to return a NULL result, nor to cope with NULL arguments
|
2000-11-20 21:36:57 +01:00
|
|
|
in any way other than making the function strict. The version-1
|
2000-08-25 01:36:29 +02:00
|
|
|
convention, presented next, overcomes these objections.
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
|
|
|
</sect2>
|
1998-03-01 09:16:16 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<sect2>
|
2000-11-20 21:36:57 +01:00
|
|
|
<title>Version-1 Calling Conventions for C-Language Functions</title>
|
2000-08-25 01:36:29 +02:00
|
|
|
|
|
|
|
<para>
|
2000-11-20 21:36:57 +01:00
|
|
|
The version-1 calling convention relies on macros to suppress most
|
2000-08-25 01:36:29 +02:00
|
|
|
of the complexity of passing arguments and results. The C declaration
|
2000-11-20 21:36:57 +01:00
|
|
|
of a version-1 function is always
|
2001-01-12 23:15:32 +01:00
|
|
|
<programlisting>
|
|
|
|
Datum funcname(PG_FUNCTION_ARGS)
|
|
|
|
</programlisting>
|
2000-11-20 21:36:57 +01:00
|
|
|
In addition, the macro call
|
2001-01-12 23:15:32 +01:00
|
|
|
<programlisting>
|
|
|
|
PG_FUNCTION_INFO_V1(funcname);
|
|
|
|
</programlisting>
|
2000-11-20 21:36:57 +01:00
|
|
|
must appear in the same source file (conventionally it's written
|
|
|
|
just before the function itself). This macro call is not needed
|
|
|
|
for "internal"-language functions, since Postgres currently assumes
|
|
|
|
all internal functions are version-1. However, it is
|
|
|
|
<emphasis>required</emphasis> for dynamically-loaded functions.
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
2001-01-12 23:15:32 +01:00
|
|
|
In a version-1 function, each actual argument is fetched using a
|
|
|
|
<function>PG_GETARG_<replaceable>xxx</replaceable>()</function>
|
|
|
|
macro that corresponds to the argument's datatype, and the result
|
|
|
|
is returned using a
|
2001-01-22 17:11:17 +01:00
|
|
|
<function>PG_RETURN_<replaceable>xxx</replaceable>()</function>
|
2001-01-12 23:15:32 +01:00
|
|
|
macro for the return type.
|
2000-08-25 01:36:29 +02:00
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
2001-01-22 17:11:17 +01:00
|
|
|
Here we show the same functions as above, coded in version-1 style:
|
2000-08-25 01:36:29 +02:00
|
|
|
|
2001-01-12 23:15:32 +01:00
|
|
|
<programlisting>
|
2000-08-25 01:36:29 +02:00
|
|
|
#include <string.h>
|
|
|
|
#include "postgres.h"
|
|
|
|
#include "fmgr.h"
|
|
|
|
|
|
|
|
/* By Value */
|
2000-11-20 21:36:57 +01:00
|
|
|
|
|
|
|
PG_FUNCTION_INFO_V1(add_one);
|
2000-08-25 01:36:29 +02:00
|
|
|
|
|
|
|
Datum
|
|
|
|
add_one(PG_FUNCTION_ARGS)
|
|
|
|
{
|
|
|
|
int32 arg = PG_GETARG_INT32(0);
|
|
|
|
|
|
|
|
PG_RETURN_INT32(arg + 1);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* By Reference, Fixed Length */
|
|
|
|
|
2000-11-20 21:36:57 +01:00
|
|
|
PG_FUNCTION_INFO_V1(add_one_float8);
|
|
|
|
|
2000-08-25 01:36:29 +02:00
|
|
|
Datum
|
|
|
|
add_one_float8(PG_FUNCTION_ARGS)
|
|
|
|
{
|
|
|
|
/* The macros for FLOAT8 hide its pass-by-reference nature */
|
|
|
|
float8 arg = PG_GETARG_FLOAT8(0);
|
|
|
|
|
|
|
|
PG_RETURN_FLOAT8(arg + 1.0);
|
|
|
|
}
|
|
|
|
|
2000-11-20 21:36:57 +01:00
|
|
|
PG_FUNCTION_INFO_V1(makepoint);
|
|
|
|
|
2000-08-25 01:36:29 +02:00
|
|
|
Datum
|
|
|
|
makepoint(PG_FUNCTION_ARGS)
|
|
|
|
{
|
2001-01-22 17:11:17 +01:00
|
|
|
/* Here, the pass-by-reference nature of Point is not hidden */
|
2000-08-25 01:36:29 +02:00
|
|
|
Point *pointx = PG_GETARG_POINT_P(0);
|
|
|
|
Point *pointy = PG_GETARG_POINT_P(1);
|
|
|
|
Point *new_point = (Point *) palloc(sizeof(Point));
|
|
|
|
|
|
|
|
new_point->x = pointx->x;
|
|
|
|
new_point->y = pointy->y;
|
|
|
|
|
|
|
|
PG_RETURN_POINT_P(new_point);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* By Reference, Variable Length */
|
|
|
|
|
2000-11-20 21:36:57 +01:00
|
|
|
PG_FUNCTION_INFO_V1(copytext);
|
|
|
|
|
2000-08-25 01:36:29 +02:00
|
|
|
Datum
|
|
|
|
copytext(PG_FUNCTION_ARGS)
|
|
|
|
{
|
|
|
|
text *t = PG_GETARG_TEXT_P(0);
|
|
|
|
/*
|
|
|
|
* VARSIZE is the total size of the struct in bytes.
|
|
|
|
*/
|
|
|
|
text *new_t = (text *) palloc(VARSIZE(t));
|
|
|
|
VARATT_SIZEP(new_t) = VARSIZE(t);
|
|
|
|
/*
|
|
|
|
* VARDATA is a pointer to the data region of the struct.
|
|
|
|
*/
|
|
|
|
memcpy((void *) VARDATA(new_t), /* destination */
|
|
|
|
(void *) VARDATA(t), /* source */
|
|
|
|
VARSIZE(t)-VARHDRSZ); /* how many bytes */
|
|
|
|
PG_RETURN_TEXT_P(new_t);
|
|
|
|
}
|
|
|
|
|
2000-11-20 21:36:57 +01:00
|
|
|
PG_FUNCTION_INFO_V1(concat_text);
|
|
|
|
|
2000-08-25 01:36:29 +02:00
|
|
|
Datum
|
|
|
|
concat_text(PG_FUNCTION_ARGS)
|
|
|
|
{
|
|
|
|
text *arg1 = PG_GETARG_TEXT_P(0);
|
|
|
|
text *arg2 = PG_GETARG_TEXT_P(1);
|
|
|
|
int32 new_text_size = VARSIZE(arg1) + VARSIZE(arg2) - VARHDRSZ;
|
|
|
|
text *new_text = (text *) palloc(new_text_size);
|
|
|
|
|
|
|
|
memset((void *) new_text, 0, new_text_size);
|
|
|
|
VARATT_SIZEP(new_text) = new_text_size;
|
|
|
|
strncpy(VARDATA(new_text), VARDATA(arg1), VARSIZE(arg1)-VARHDRSZ);
|
|
|
|
strncat(VARDATA(new_text), VARDATA(arg2), VARSIZE(arg2)-VARHDRSZ);
|
|
|
|
PG_RETURN_TEXT_P(new_text);
|
|
|
|
}
|
2001-01-12 23:15:32 +01:00
|
|
|
</programlisting>
|
2000-08-25 01:36:29 +02:00
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
The <command>CREATE FUNCTION</command> commands are the same as
|
2001-01-22 17:11:17 +01:00
|
|
|
for the version-0 equivalents.
|
2000-08-25 01:36:29 +02:00
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
2001-01-12 23:15:32 +01:00
|
|
|
At first glance, the version-1 coding conventions may appear to
|
|
|
|
be just pointless obscurantism. However, they do offer a number
|
|
|
|
of improvements, because the macros can hide unnecessary detail.
|
2000-08-25 01:36:29 +02:00
|
|
|
An example is that in coding add_one_float8, we no longer need to
|
2001-01-12 23:15:32 +01:00
|
|
|
be aware that float8 is a pass-by-reference type. Another
|
|
|
|
example is that the GETARG macros for variable-length types hide
|
|
|
|
the need to deal with fetching "toasted" (compressed or
|
|
|
|
out-of-line) values. The old-style <function>copytext</function>
|
|
|
|
and <function>concat_text</function> functions shown above are
|
|
|
|
actually wrong in the presence of toasted values, because they
|
|
|
|
don't call <function>pg_detoast_datum()</function> on their
|
|
|
|
inputs. (The handler for old-style dynamically-loaded functions
|
|
|
|
currently takes care of this detail, but it does so less
|
|
|
|
efficiently than is possible for a version-1 function.)
|
2000-08-25 01:36:29 +02:00
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
2000-11-20 21:36:57 +01:00
|
|
|
The version-1 function call conventions also make it possible to
|
2001-01-12 23:15:32 +01:00
|
|
|
test for NULL inputs to a non-strict function, return a NULL
|
|
|
|
result (from either strict or non-strict functions), return
|
|
|
|
<quote>set</quote> results, and implement trigger functions and
|
2001-01-22 17:11:17 +01:00
|
|
|
procedural-language call handlers. Version-1 code is also more
|
|
|
|
portable than version-0, because it does not break ANSI C restrictions
|
|
|
|
on function call protocol. For more details see
|
2001-01-12 23:15:32 +01:00
|
|
|
<filename>src/backend/utils/fmgr/README</filename> in the source
|
|
|
|
distribution.
|
2000-08-25 01:36:29 +02:00
|
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
|
|
|
|
<sect2>
|
|
|
|
<title>Composite Types in C-Language Functions</title>
|
1998-03-01 09:16:16 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<para>
|
1998-03-01 09:16:16 +01:00
|
|
|
Composite types do not have a fixed layout like C
|
|
|
|
structures. Instances of a composite type may contain
|
|
|
|
null fields. In addition, composite types that are
|
|
|
|
part of an inheritance hierarchy may have different
|
|
|
|
fields than other members of the same inheritance hierarchy.
|
1999-07-22 17:11:05 +02:00
|
|
|
Therefore, <productname>Postgres</productname> provides
|
1999-03-14 16:24:15 +01:00
|
|
|
a procedural interface for accessing fields of composite types
|
1999-07-22 17:11:05 +02:00
|
|
|
from C. As <productname>Postgres</productname> processes
|
2001-01-14 00:58:55 +01:00
|
|
|
a set of rows, each row will be passed into your
|
1999-10-04 17:18:54 +02:00
|
|
|
function as an opaque structure of type <literal>TUPLE</literal>.
|
1998-03-01 09:16:16 +01:00
|
|
|
Suppose we want to write a function to answer the query
|
1999-07-22 17:11:05 +02:00
|
|
|
|
2001-01-12 23:15:32 +01:00
|
|
|
<programlisting>
|
|
|
|
SELECT name, c_overpaid(emp, 1500) AS overpaid
|
|
|
|
FROM emp
|
|
|
|
WHERE name = 'Bill' OR name = 'Sam';
|
|
|
|
</programlisting>
|
1999-07-22 17:11:05 +02:00
|
|
|
|
1998-03-01 09:16:16 +01:00
|
|
|
In the query above, we can define c_overpaid as:
|
|
|
|
|
2001-01-12 23:15:32 +01:00
|
|
|
<programlisting>
|
2000-05-02 22:02:03 +02:00
|
|
|
#include "postgres.h"
|
|
|
|
#include "executor/executor.h" /* for GetAttributeByName() */
|
|
|
|
|
|
|
|
bool
|
2001-01-14 00:58:55 +01:00
|
|
|
c_overpaid(TupleTableSlot *t, /* the current row of EMP */
|
2000-08-25 01:36:29 +02:00
|
|
|
int32 limit)
|
2000-05-02 22:02:03 +02:00
|
|
|
{
|
2000-08-25 01:36:29 +02:00
|
|
|
bool isnull;
|
|
|
|
int32 salary;
|
|
|
|
|
|
|
|
salary = DatumGetInt32(GetAttributeByName(t, "salary", &isnull));
|
2000-05-02 22:02:03 +02:00
|
|
|
if (isnull)
|
|
|
|
return (false);
|
2000-08-25 01:36:29 +02:00
|
|
|
return salary > limit;
|
|
|
|
}
|
|
|
|
|
2000-11-20 21:36:57 +01:00
|
|
|
/* In version-1 coding, the above would look like this: */
|
|
|
|
|
|
|
|
PG_FUNCTION_INFO_V1(c_overpaid);
|
2000-08-25 01:36:29 +02:00
|
|
|
|
|
|
|
Datum
|
|
|
|
c_overpaid(PG_FUNCTION_ARGS)
|
|
|
|
{
|
|
|
|
TupleTableSlot *t = (TupleTableSlot *) PG_GETARG_POINTER(0);
|
|
|
|
int32 limit = PG_GETARG_INT32(1);
|
|
|
|
bool isnull;
|
|
|
|
int32 salary;
|
|
|
|
|
|
|
|
salary = DatumGetInt32(GetAttributeByName(t, "salary", &isnull));
|
|
|
|
if (isnull)
|
|
|
|
PG_RETURN_BOOL(false);
|
|
|
|
/* Alternatively, we might prefer to do PG_RETURN_NULL() for null salary */
|
|
|
|
|
|
|
|
PG_RETURN_BOOL(salary > limit);
|
2000-05-02 22:02:03 +02:00
|
|
|
}
|
2001-01-12 23:15:32 +01:00
|
|
|
</programlisting>
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
1998-03-01 09:16:16 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<para>
|
1999-10-04 17:18:54 +02:00
|
|
|
<function>GetAttributeByName</function> is the
|
1999-07-22 17:11:05 +02:00
|
|
|
<productname>Postgres</productname> system function that
|
2001-01-14 00:58:55 +01:00
|
|
|
returns attributes out of the current row. It has
|
2001-01-12 23:15:32 +01:00
|
|
|
three arguments: the argument of type <type>TupleTableSlot*</type> passed into
|
1998-03-01 09:16:16 +01:00
|
|
|
the function, the name of the desired attribute, and a
|
2000-08-25 01:36:29 +02:00
|
|
|
return parameter that tells whether the attribute
|
|
|
|
is null. <function>GetAttributeByName</function> returns a Datum
|
|
|
|
value that you can convert to the proper datatype by using the
|
2001-01-12 23:15:32 +01:00
|
|
|
appropriate <function>DatumGet<replaceable>XXX</replaceable>()</function> macro.
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
1998-03-01 09:16:16 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<para>
|
|
|
|
The following query lets <productname>Postgres</productname>
|
2001-01-12 23:15:32 +01:00
|
|
|
know about the <function>c_overpaid</function> function:
|
1999-07-22 17:11:05 +02:00
|
|
|
|
2001-01-12 23:15:32 +01:00
|
|
|
<programlisting>
|
|
|
|
CREATE FUNCTION c_overpaid(emp, int4)
|
2000-05-20 13:24:37 +02:00
|
|
|
RETURNS bool
|
|
|
|
AS '<replaceable>PGROOT</replaceable>/tutorial/obj/funcs.so'
|
|
|
|
LANGUAGE 'c';
|
2001-01-12 23:15:32 +01:00
|
|
|
</programlisting>
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
1998-03-01 09:16:16 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<para>
|
2001-01-14 00:58:55 +01:00
|
|
|
While there are ways to construct new rows or modify
|
|
|
|
existing rows from within a C function, these
|
1998-03-01 09:16:16 +01:00
|
|
|
are far too complex to discuss in this manual.
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
|
|
|
</sect2>
|
1998-03-01 09:16:16 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<sect2>
|
|
|
|
<title>Writing Code</title>
|
1998-03-01 09:16:16 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<para>
|
1998-03-01 09:16:16 +01:00
|
|
|
We now turn to the more difficult task of writing
|
|
|
|
programming language functions. Be warned: this section
|
|
|
|
of the manual will not make you a programmer. You must
|
2001-01-12 23:15:32 +01:00
|
|
|
have a good understanding of <acronym>C</acronym>
|
1999-03-14 16:24:15 +01:00
|
|
|
(including the use of pointers and the malloc memory manager)
|
1999-07-22 17:11:05 +02:00
|
|
|
before trying to write <acronym>C</acronym> functions for
|
|
|
|
use with <productname>Postgres</productname>. While it may
|
1999-03-14 16:24:15 +01:00
|
|
|
be possible to load functions written in languages other
|
1999-07-22 17:11:05 +02:00
|
|
|
than <acronym>C</acronym> into <productname>Postgres</productname>,
|
1999-03-14 16:24:15 +01:00
|
|
|
this is often difficult (when it is possible at all)
|
1999-07-22 17:11:05 +02:00
|
|
|
because other languages, such as <acronym>FORTRAN</acronym>
|
|
|
|
and <acronym>Pascal</acronym> often do not follow the same
|
|
|
|
<firstterm>calling convention</firstterm>
|
|
|
|
as <acronym>C</acronym>. That is, other
|
1998-03-01 09:16:16 +01:00
|
|
|
languages do not pass argument and return values
|
|
|
|
between functions in the same way. For this reason, we
|
|
|
|
will assume that your programming language functions
|
1999-07-22 17:11:05 +02:00
|
|
|
are written in <acronym>C</acronym>.
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
The basic rules for building <acronym>C</acronym> functions
|
1999-03-14 16:24:15 +01:00
|
|
|
are as follows:
|
1998-03-01 09:16:16 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<itemizedlist>
|
|
|
|
<listitem>
|
|
|
|
<para>
|
2001-01-12 23:15:32 +01:00
|
|
|
The relevant header (include) files are installed under
|
|
|
|
<filename>/usr/local/pgsql/include</filename> or equivalent.
|
|
|
|
You can use <literal>pg_config --includedir</literal> to find
|
|
|
|
out where it is on your system (or the system that your
|
|
|
|
users will be running on). For very low-level work you might
|
|
|
|
need to have a complete <productname>PostgreSQL</productname>
|
|
|
|
source tree available.
|
|
|
|
</para>
|
|
|
|
</listitem>
|
1999-07-22 17:11:05 +02:00
|
|
|
|
2001-01-12 23:15:32 +01:00
|
|
|
<listitem>
|
|
|
|
<para>
|
|
|
|
When allocating memory, use the
|
|
|
|
<productname>Postgres</productname> routines
|
|
|
|
<function>palloc</function> and <function>pfree</function>
|
|
|
|
instead of the corresponding <acronym>C</acronym> library
|
|
|
|
routines <function>malloc</function> and
|
|
|
|
<function>free</function>. The memory allocated by
|
|
|
|
<function>palloc</function> will be freed automatically at the
|
|
|
|
end of each transaction, preventing memory leaks.
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
|
|
|
</listitem>
|
2001-01-12 23:15:32 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<listitem>
|
|
|
|
<para>
|
2001-01-12 23:15:32 +01:00
|
|
|
Always zero the bytes of your structures using
|
|
|
|
<function>memset</function> or <function>bzero</function>.
|
|
|
|
Several routines (such as the hash access method, hash join
|
|
|
|
and the sort algorithm) compute functions of the raw bits
|
|
|
|
contained in your structure. Even if you initialize all
|
|
|
|
fields of your structure, there may be several bytes of
|
|
|
|
alignment padding (holes in the structure) that may contain
|
|
|
|
garbage values.
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
|
|
|
</listitem>
|
2001-01-12 23:15:32 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<listitem>
|
|
|
|
<para>
|
2001-01-12 23:15:32 +01:00
|
|
|
Most of the internal <productname>Postgres</productname> types
|
|
|
|
are declared in <filename>postgres.h</filename>, the function
|
|
|
|
manager interfaces (<symbol>PG_FUNCTION_ARGS</symbol>, etc.)
|
|
|
|
are in <filename>fmgr.h</filename>, so you will need to
|
|
|
|
include at least these two files. Including
|
|
|
|
<filename>postgres.h</filename> will also include
|
|
|
|
<filename>elog.h</filename> and <filename>palloc.h</filename>
|
|
|
|
for you.
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
|
|
|
</listitem>
|
2001-01-12 23:15:32 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<listitem>
|
|
|
|
<para>
|
2001-01-12 23:15:32 +01:00
|
|
|
Symbol names defined within object files must not conflict
|
|
|
|
with each other or with symbols defined in the
|
|
|
|
<productname>PostgreSQL</productname> server executable. You
|
|
|
|
will have to rename your functions or variables if you get
|
|
|
|
error messages to this effect.
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
|
|
|
</listitem>
|
2001-01-12 23:15:32 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<listitem>
|
|
|
|
<para>
|
2001-01-20 21:59:29 +01:00
|
|
|
Compiling and linking your object code so that
|
1999-07-22 17:11:05 +02:00
|
|
|
it can be dynamically loaded into
|
|
|
|
<productname>Postgres</productname>
|
|
|
|
always requires special flags.
|
2000-12-26 01:10:37 +01:00
|
|
|
See <xref linkend="dfunc">
|
1999-07-22 17:11:05 +02:00
|
|
|
for a detailed explanation of how to do it for
|
|
|
|
your particular operating system.
|
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</itemizedlist>
|
|
|
|
</para>
|
|
|
|
</sect2>
|
2001-01-12 23:15:32 +01:00
|
|
|
|
|
|
|
&dfunc;
|
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
</sect1>
|
|
|
|
|
2000-09-29 22:21:34 +02:00
|
|
|
<sect1 id="xfunc-overload">
|
1999-07-22 17:11:05 +02:00
|
|
|
<title>Function Overloading</title>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
More than one function may be defined with the same name, as long as
|
|
|
|
the arguments they take are different. In other words, function names
|
|
|
|
can be <firstterm>overloaded</firstterm>.
|
|
|
|
A function may also have the same name as an attribute. In the case
|
|
|
|
that there is an ambiguity between a function on a complex type and
|
|
|
|
an attribute of the complex type, the attribute will always be used.
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<sect2>
|
|
|
|
<title>Name Space Conflicts</title>
|
|
|
|
|
|
|
|
<para>
|
2000-12-21 23:55:27 +01:00
|
|
|
As of <productname>Postgres</productname> 7.0, the alternative
|
1999-10-01 17:20:06 +02:00
|
|
|
form of the AS clause for the SQL
|
|
|
|
<command>CREATE FUNCTION</command> command
|
|
|
|
decouples the SQL function name from the function name in the C
|
|
|
|
source code. This is now the preferred technique to accomplish
|
|
|
|
function overloading.
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
|
|
|
|
|
|
|
<sect3>
|
2000-12-21 23:55:27 +01:00
|
|
|
<title>Pre-7.0</title>
|
1999-07-22 17:11:05 +02:00
|
|
|
|
|
|
|
<para>
|
|
|
|
For functions written in C, the SQL name declared in
|
2000-05-27 20:18:31 +02:00
|
|
|
<command>CREATE FUNCTION</command>
|
1999-07-22 17:11:05 +02:00
|
|
|
must be exactly the same as the actual name of the function in the
|
|
|
|
C code (hence it must be a legal C function name).
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
There is a subtle implication of this restriction: while the
|
|
|
|
dynamic loading routines in most operating systems are more than
|
|
|
|
happy to allow you to load any number of shared libraries that
|
|
|
|
contain conflicting (identically-named) function names, they may
|
|
|
|
in fact botch the load in interesting ways. For example, if you
|
|
|
|
define a dynamically-loaded function that happens to have the
|
|
|
|
same name as a function built into Postgres, the DEC OSF/1 dynamic
|
|
|
|
loader causes Postgres to call the function within itself rather than
|
|
|
|
allowing Postgres to call your function. Hence, if you want your
|
|
|
|
function to be used on different architectures, we recommend that
|
|
|
|
you do not overload C function names.
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
There is a clever trick to get around the problem just described.
|
|
|
|
Since there is no problem overloading SQL functions, you can
|
|
|
|
define a set of C functions with different names and then define
|
|
|
|
a set of identically-named SQL function wrappers that take the
|
|
|
|
appropriate argument types and call the matching C function.
|
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
Another solution is not to use dynamic loading, but to link your
|
|
|
|
functions into the backend statically and declare them as INTERNAL
|
|
|
|
functions. Then, the functions must all have distinct C names but
|
|
|
|
they can be declared with the same SQL names (as long as their
|
|
|
|
argument types differ, of course). This way avoids the overhead of
|
|
|
|
an SQL wrapper function, at the cost of more effort to prepare a
|
1999-10-02 23:27:49 +02:00
|
|
|
custom backend executable. (This option is only available in version
|
|
|
|
6.5 and later, since prior versions required internal functions to
|
|
|
|
have the same name in SQL as in the C code.)
|
1999-07-22 17:11:05 +02:00
|
|
|
</para>
|
|
|
|
</sect3>
|
|
|
|
</sect2>
|
|
|
|
</sect1>
|
|
|
|
</chapter>
|
1998-12-29 03:24:47 +01:00
|
|
|
|
1999-07-22 17:11:05 +02:00
|
|
|
<!-- Keep this comment at the end of the file
|
|
|
|
Local variables:
|
2000-03-31 05:27:42 +02:00
|
|
|
mode:sgml
|
1999-07-22 17:11:05 +02:00
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|
|
sgml-omittag:nil
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sgml-shorttag:t
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|
sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
|
|
|
|
sgml-indent-step:1
|
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|
|
sgml-indent-data:t
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|
|
sgml-parent-document:nil
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|
|
|
sgml-default-dtd-file:"./reference.ced"
|
|
|
|
sgml-exposed-tags:nil
|
2000-03-31 05:27:42 +02:00
|
|
|
sgml-local-catalogs:("/usr/lib/sgml/catalog")
|
1999-07-22 17:11:05 +02:00
|
|
|
sgml-local-ecat-files:nil
|
|
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|
End:
|
|
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|
-->
|