kamailio/doc/tutorials/serdev/db_interface.xml

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<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" 
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<section id="db_interface" xmlns:xi="http://www.w3.org/2001/XInclude">
    <sectioninfo>
	<revhistory>
	    <revision>
		<revnumber>$Revision$</revnumber>
		<date>$Date$</date>
	    </revision>
	</revhistory>
    </sectioninfo>

    <title>The Database Interface</title>
    <para>
	This is a generic database interface for modules that need to utilize a
	database. The interface should be used by all modules that access
	database.  The interface will be independent of the underlying database
	server.
    </para>
    <note>
	<para>
	    If possible, use predefined macros if you need to access any
	    structure attributes.
	</para>
	<para>
	    For additional description, see comments in sources of mysql
	    module.
	</para>
	<para>
	    If you want to see more complicated examples of how the API could
	    be used, see sources of dbexample, usrloc or auth modules.
	</para>
    </note>
    
    <section id="data_types">
	<title>Data types</title>
	<para>
	    There are several data types. All of them are defined in header
	    files under <filename>db</filename> subdirectory, a client must
	    include <filename>db.h</filename> header file to be able to use
	    them.
	</para>

	<xi:include href="db_con_t.xml"/>
	<xi:include href="db_key_t.xml"/>
	<xi:include href="db_type_t.xml"/>
	<xi:include href="db_val_t.xml"/>
	<xi:include href="db_row_t.xml"/>
	<xi:include href="db_res_t.xml"/>
    </section>
	
    <section id="db_functions">
	<title>Functions</title>
	<para>
	    There are several functions that implement the database
	    <acronym>API</acronym> logic. All function names start with db_
	    prefix, except <function>bind_dbmod</function>.
	    <function>bind_dbmod</function> is implemented in
	    <filename>db.c</filename> file, all other functions are implemented
	    in a standalone module.  Detailed description of functions follows.
	</para>
	
	<section id="bind_dbmod">
	    <title><function>bind_dbmod</function></title>
	    <para>
		This function is special, it's only purpose is to call
		<function>find_export</function> function in the
		<acronym>SER</acronym> core and find addresses of all other
		functions (starting with db_ prefix). This function
		<emphasis>MUST</emphasis> be called <emphasis>FIRST</emphasis>
		!
	    </para>
	    <funcsynopsis>
		<funcprototype>
		    <funcdef>int <function>bind_dbmod</function></funcdef>
		    <void/>
		</funcprototype>
	    </funcsynopsis>
	    <para>
		The function takes no parameters.
	    </para>
	    <para>
		The function returns 0 if it was able to find addresses of all
		other functions, otherwise value &lt; 0 is returned.
	    </para>
	</section> <!-- bind_dbmod -->
	
	<section id="db_init">
	    <title><function>db_init</function></title>
	    <para>
		Use this function to initialize the database
		<acronym>API</acronym> and open a new database connection. This
		function must be called after <function>bind_dbmod</function>
		but before any other function is called.
	    </para>
	    <funcsynopsis>
		<funcprototype>
		    <funcdef>db_con_t* <function>db_init</function></funcdef>
		    <paramdef>const char* <parameter>_sql_url</parameter></paramdef>
		</funcprototype>
	    </funcsynopsis>
	    <para>
		The function takes one parameter, the parameter must contain
		database connection <acronym>URL</acronym>. The
		<acronym>URL</acronym> is of the form
		mysql://username:password@host:port/database where:
		<itemizedlist>
		    <listitem>
			<para>
			    <emphasis>username</emphasis> - Username to use
			    when logging into database (optional).
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <emphasis>password</emphasis> - Password if it was
			    set (optional).
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <emphasis>host</emphasis> - Hostname or IP address
			    of the host where database server lives
			    (mandatory).
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <emphasis>port</emphasis> - Port number of the
			    server if the port differs from default value
			    (optional).
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <emphasis>database</emphasis> - If the database server supports 
			    multiple databases, you must specify name of the database (optional).
			</para>
		    </listitem>
		</itemizedlist>
	    </para>
	    <para>
		The function returns pointer to <type>db_con_t</type>*
		representing the connection if it was successful, otherwise 0
		is returned.
	    </para>
	</section> <!-- db-init -->
	
	<section id="db_close">
	    <title><function>db_close</function></title>
	    <para>
		The function closes previously open connection and frees all
		previously allocated memory. The function
		<function>db_close</function> must be the very last function
		called.
	    </para>
		<funcsynopsis>
		<funcprototype>
		    <funcdef>void <function>db_close</function></funcdef>
		    <paramdef>db_con_t* <parameter>_h</parameter></paramdef>
		</funcprototype>
	    </funcsynopsis>
	    <para>
		The function takes one parameter, this parameter is a pointer
		to <type>db_con_t</type> structure representing database
		connection that should be closed.
	    </para>
	    <para>
		Function doesn't return anything.
	    </para>
	</section> <!-- db-close -->
	
	<section id="db_query">
	    <title><function>db_query</function></title>
	    <para>
		This function implements SELECT <acronym>SQL</acronym> directive.
	    </para>
	    <funcsynopsis>
		<funcprototype>
		    <funcdef>int <function>db_query</function></funcdef>
		    <paramdef>db_con_t* <parameter>_h</parameter></paramdef>
		    <paramdef>db_key_t* <parameter>_k</parameter></paramdef>
		    <paramdef>db_val_t* <parameter>_v</parameter></paramdef>
		    <paramdef>db_key_t* <parameter>_c</parameter></paramdef>
		    <paramdef>int <parameter>_n</parameter></paramdef>
		    <paramdef>int <parameter>_nc</parameter></paramdef>
		    <paramdef>db_key_t* <parameter>_o</parameter></paramdef>
		    <paramdef>db_res_t** <parameter>_r</parameter></paramdef>
		</funcprototype>
	    </funcsynopsis>
	    <para>
		The function takes 8 parameters:
		<itemizedlist>
		    <listitem>
			<para>
			    <emphasis>_h</emphasis> - Database connection handle.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <emphasis>_k</emphasis> - Array of column names
			    that will be compared and their values must
			    match.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <emphasis>_v</emphasis> - Array of values,
			    columns specified in _k parameter must match
			    these values.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <emphasis>_c</emphasis> - Array of column names
			    that you are interested in.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <emphasis>_n</emphasis> - Number of key-value
			    pairs to match in _k and _v parameters.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <emphasis>_nc</emphasis> - Number of columns in
			    _c parameter.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <emphasis>_o</emphasis> - Order by.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <emphasis>_r</emphasis> - Address of variable
				where pointer to the result will be stored.
			</para>
		    </listitem>
		</itemizedlist>
		If _k and _v parameters are NULL and _n is zero, you will get
		the whole table.  If _c is NULL and _nc is zero, you will get
		all table columns in the result
	    </para>
	    <para>
		_r will point to a dynamically allocated structure, it is
		necessary to call db_free_result function once you are finished
		with the result.
	    </para>
	    <para>
		Strings in the result are not duplicated, they will be
		discarded if you call db_free_result, make a copy yourself if
		you need to keep it after db_free_result.
	    </para>
	    <para>
		You must call db_free_result <emphasis>BEFORE</emphasis> you
		can call db_query again !
	    </para>
	    <para>
		The function returns 0 if everything is OK, otherwise value
		&lt; 0 is returned.
	    </para>
	</section> <!-- db_query -->
	
	<section id="db_free_result">
	    <title><function>db_free_result</function></title>
	    <para>
		This function frees all memory allocated previously in
		<function>db_query</function>, it is necessary to call this
		function for a <type>db_res_t</type> structure if you don't
		need the structure anymore. You must call this function
		<emphasis>BEFORE</emphasis> you call
		<function>db_query</function> again !
	    </para>
	    <funcsynopsis>
		<funcprototype>
		    <funcdef>int <function>db_free_result</function></funcdef>
		    <paramdef>db_con_t* <parameter>_h</parameter></paramdef>
		    <paramdef>db_res_t* <parameter>_r</parameter></paramdef>
		</funcprototype>
	    </funcsynopsis>
	    <para>
		The function takes 2 parameters:
		<itemizedlist>
		    <listitem>
			<para>
			    <parameter>_h</parameter> - Database connection handle.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <parameter>_r</parameter> - Pointer to db_res_t
			    structure to destroy.
			</para>
		    </listitem>
		</itemizedlist>
	    </para>
	    <para>
		The function returns 0 if everything is OK, otherwise the
		function returns value &lt; 0.
	    </para>
	</section> <!-- db_free_result -->
	
	<section id="db_insert">
	    <title><function>db_insert</function></title>
	    <para>
		This function implements INSERT SQL directive, you can
		insert one or more rows in a table using this function.
	    </para>
	    <funcsynopsis>
		<funcprototype>
		    <funcdef>int <function>db_insert</function></funcdef>
		    <paramdef>db_con_t* <parameter>_h</parameter></paramdef>
		    <paramdef>db_key_t* <parameter>_k</parameter></paramdef>
		    <paramdef>db_val_t* <parameter>_v</parameter></paramdef>
		    <paramdef>int <parameter>_n</parameter></paramdef>
		</funcprototype>
	    </funcsynopsis>
	    <para>
		The function takes 4 parameters:
		<itemizedlist>
		    <listitem>
			<para>
			    <parameter>_h</parameter> - Database connection handle.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <parameter>_k</parameter> - Array of keys (column names).
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <parameter>_v</parameter> - Array of values for
			    keys specified in _k parameter.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <parameter>_n</parameter> - Number of
			    keys-value pairs int _k and _v parameters.
			    </para>
		    </listitem>
		</itemizedlist>
	    </para>
	    <para>
		The function returns 0 if everything is OK, otherwise the
		function returns value &lt; 0.
	    </para>
	</section> <!-- db_insert -->
	
	<section id="db_delete">
	    <title><function>db_delete</function></title>
	    <para>
		This function implements DELETE SQL directive, it is
		possible to delete one or more rows from a table.
	    </para>
	    <funcsynopsis>
		<funcprototype>
		    <funcdef>int <function>db_delete</function></funcdef>
		    <paramdef>db_con_t* <parameter>_h</parameter></paramdef>
		    <paramdef>db_key_t* <parameter>_k</parameter></paramdef>
		    <paramdef>db_val_t* <parameter>_v</parameter></paramdef>
		    <paramdef>int <parameter>_n</parameter></paramdef>
		</funcprototype>
	    </funcsynopsis>
	    <para>
		The function takes 4 parameters:
		<itemizedlist>
		    <listitem>
			<para>
			    <parameter>_h</parameter> - Database connection handle.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <parameter>_k</parameter> - Array of keys
			    (column names) that will be matched.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <parameter>_v</parameter> - Array of values
			    that the row must match to be deleted.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <parameter>_n</parameter> - Number of
			    keys-value parameters in _k and _v parameters.
			</para>
		    </listitem>
		</itemizedlist>
		If _k is NULL and _v is NULL and _n is zero, all rows are
		deleted (table will be empty).
	    </para>
	    <para>
		The function returns 0 if everything is OK, otherwise the
		function returns value &lt; 0.
	    </para>
	</section> <!-- db_delete -->
	
	<section id="db_update">
	    <title><function>db_update</function></title>
	    <para>
		The function implements UPDATE SQL directive. It is possible to
		modify one or more rows in a table using this function.
	    </para>
		<funcsynopsis>
		<funcprototype>
		    <funcdef>int <function>db_update</function></funcdef>
		    <paramdef>db_con_t* <parameter>_h</parameter></paramdef>
		    <paramdef>db_key_t* <parameter>_k</parameter></paramdef>
		    <paramdef>db_val_t* <parameter>_v</parameter></paramdef>
		    <paramdef>db_key_t* <parameter>_uk</parameter></paramdef>
		    <paramdef>db_val_t* <parameter>_uv</parameter></paramdef>
		    <paramdef>int <parameter>_n</parameter></paramdef>
		    <paramdef>int <parameter>_un</parameter></paramdef>
		</funcprototype>
	    </funcsynopsis>
	    <para>
		The function takes 7 parameters:
		<itemizedlist>
		    <listitem>
			<para>
			    <parameter>_h</parameter> - Database connection handle.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <parameter>_k</parameter> - Array of keys (column names) that will be matched.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <parameter>_v</parameter> - Array of values that the row must match 
			    to be modified.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <parameter>_uk</parameter> - Array of keys (column names) that will be modified.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <parameter>_uv</parameter> - New values for keys specified in _k parameter.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <parameter>_n</parameter> - Number of key-value pairs in _k and _v parameters.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <parameter>_un</parameter> - Number of key-value pairs 
			    in _uk and _uv parameters.
			</para>
		    </listitem>
		</itemizedlist>
	    </para>
	    <para>
		The function returns 0 if everything is OK, otherwise the function returns
		value &lt; 0.
	    </para>
	</section> <!-- db_update -->

	<section id="db_use_table">
	    <title><function>db_use_table</function></title>
	    <para>
		The function db_use_table takes a table name and stores it
		in db_con_t structure.  All subsequent operations (insert,
		delete, update, query) are performed on that table.
	    </para>
	    <funcsynopsis>
		<funcprototype>
		    <funcdef>int <function>db_use-table</function></funcdef>
		    <paramdef>db_con_t* <parameter>_h</parameter></paramdef>
		    <paramdef>cons char* <parameter>_t</parameter></paramdef>
		</funcprototype>
	    </funcsynopsis>
	    <para>
		The function takes 2 parameters:
		<itemizedlist>
		    <listitem>
			<para>
			    <parameter>_h</parameter> - Database connection handle.
			</para>
		    </listitem>
		    <listitem>
			<para>
			    <parameter>_t</parameter> - Table name.
			</para>
		    </listitem>
		</itemizedlist>
	    </para>
	    <para>
		The function returns 0 if everything is OK, otherwise the
		function returns value &lt; 0.
	    </para>
	</section>
    </section>
</section>