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<!-- Module User's Guide -->

<chapter xmlns:xi="http://www.w3.org/2001/XInclude">
	<title>&adminguide;</title>

	<section>
	<title>Overview</title>
	<para>
		The module implements a simplified database engine based on text
		files. It can be used by &kamailio; DB interface instead of other
		database module (like MySQL).
	</para>
	<para>
		The module is meant for use in demos or small devices that do not
		support other DB modules. It keeps everything in memory and if you deal
		with large amount of data you may run quickly out of memory. Also, it
		has not implemented all standard database facilities (like order by),
		it includes minimal functionality to work properly (who knows ?!?)
		with &kamailio;.
	</para>
	<para>
		NOTE: the timestamp is printed in an integer value from time_t
		structure. If you use it in a system that cannot do this conversion,
		it will fail (support for such situation is in to-do list).
	</para>
	<para>
		NOTE: even when is in non-caching mode, the module does not write
		back to hard drive after changes. In this mode, the module checks if
		the corresponding file on disk has changed, and reloads it. The write
		on disk happens at openser shut down.
	</para>
		<section>
		<title>Design of dbtext engine</title>
		<para>
		The dbtext database system architecture:
			<itemizedlist>
			<listitem>
				<para>
				a database is represented by a directory in the local file
				system.
				NOTE: when you use <emphasis>dbtext</emphasis> in &kamailio;,
				the	database URL for modules must be the path to the directory
				where the table-files are located, prefixed by 
				<quote>dbtext://</quote>, e.g., 
				<quote>dbtext:///var/dbtext/ser</quote>. If there is no
				<quote>/</quote> after <quote>dbtext://</quote> then
				<quote>CFG_DIR/</quote> is inserted at the beginning of the
				database path. So, either you provide an absolute path to
				database directory or a relative one to <quote>CFG_DIR</quote>
				directory.
				</para>
			</listitem>
			<listitem>
				<para>
				a table is represented by a text file inside database directory.
				</para>
			</listitem>
			</itemizedlist>
		</para>
		</section>
		<section>
		<title>Internal format of a dbtext table</title>
		<para>
		First line is the definition of the columns. Each column must be
		declared as follows:
			<itemizedlist>
			<listitem>
				<para>
				the name of column must not include white spaces.
				</para>
			</listitem>
			<listitem>
				<para>
				the format of a column definition is: 
				<emphasis>name(type,attr)</emphasis>.
				</para>
			</listitem>
			<listitem>
				<para>
				between two column definitions must be a white space, e.g., 
				<quote>first_name(str) last_name(str)</quote>.
				</para>
			</listitem>
			<listitem>
				<para>
				the type of a column can be: 
					<itemizedlist>
					<listitem>
					<para>
					<emphasis>int</emphasis> - integer numbers.
					</para>
					</listitem>
					<listitem>
					<para>
					<emphasis>double</emphasis> - real numbers with two
					decimals.
					</para>
					</listitem>
					<listitem>
					<para>
					<emphasis>str</emphasis> - strings with maximum size of 4KB.
					</para>
					</listitem>
					</itemizedlist>
				</para>
			</listitem>
			<listitem>
				<para>
				a column can have one of the attributes: 
					<itemizedlist>
					<listitem>
					<para>
					<emphasis>auto</emphasis> - only for 'int' columns,
					the maximum value in that column is incremented and stored
					in this field if it is not provided in queries.
					</para>
					</listitem>
					<listitem>
					<para>
					<emphasis>null</emphasis> - accept null values in column
					fields.
					</para>
					</listitem>
					<listitem>
					<para>
					if no attribute is set, the fields of the column cannot have
					null value.
					</para>
					</listitem>
					</itemizedlist>
				</para>
			</listitem>
			<listitem>
				<para>
				each other line is a row with data. The line ends with
				<quote>\n</quote>.
				</para>
			</listitem>
			<listitem>
				<para>
				the fields are separated by <quote>:</quote>.
				</para>
			</listitem>
			<listitem>
				<para>
				no value between two ':' (or between ':' and start/end of a row)
				means <quote>null</quote> value.
				</para>
			</listitem>
			<listitem>
				<para>
				next characters must be escaped in strings: <quote>\n</quote>,
				<quote>\r</quote>, <quote>\t</quote>, <quote>:</quote>.
				</para>
			</listitem>
			<listitem>
				<para>
				 <emphasis>0</emphasis> -- the zero value must be escaped too.
				</para>
			</listitem>
			</itemizedlist>
		</para>
		<example>
		<title>Sample of a dbtext table</title>
<programlisting format="linespecific">
...
id(int,auto) name(str) flag(double) desc(str,null)
1:nick:0.34:a\tgood\: friend
2:cole:-3.75:colleague
3:bob:2.50:
...
</programlisting>
		</example>
		<example>
		<title>Minimal &kamailio; location dbtext table definition</title>
<programlisting format="linespecific">
...
username(str) contact(str) expires(int) q(double) callid(str) cseq(int)
...
</programlisting>
		</example>
		<example>
		<title>Minimal &kamailio; subscriber dbtext table example</title>
<programlisting format="linespecific">
...
username(str) password(str) ha1(str) domain(str) ha1b(str)
suser:supasswd:xxx:alpha.org:xxx
...
</programlisting>
		</example>
		</section>
		<section>
		<title>Existing limitations</title>
		<para>This database interface don't support the data insertion with
				default values. All such values specified in the database template
				are ignored. So its advisable to specify all data for a column at
				insertion operations.
		</para>
		</section>
	</section>
	<section>
	<title>Dependencies</title>
		<section>
			<title>&kamailio; modules</title>
		<para>
			The next modules must be loaded before this module:
			<itemizedlist>
			<listitem>
				<para>
				<emphasis>none</emphasis>.
				</para>
			</listitem>
			</itemizedlist>
		</para>
		</section>
		<section>
			<title>External libraries or applications</title>
		<para>
			The next libraries or applications must be installed before running
			&kamailio; with this module:
			<itemizedlist>
			<listitem>
				<para>
				<emphasis>none</emphasis>.
				</para>
			</listitem>
			</itemizedlist>
		</para>
		</section>
	</section>
	<section>
	<title>Exported Parameters</title>
		<para>
			<emphasis>None</emphasis>.
	   	</para>
		<section>
			<title><varname>db_mode</varname> (integer)</title>
		<para>
		Set caching mode (0) or non-caching mode (1). In caching mode, data
		is loaded at startup. In non-caching mode, the module check every time
		a table is requested whether the corresponding file on disk has
		changed, and if yes, will re-load table from file.
		</para>
		<para>
		<emphasis>
			Default value is <quote>0</quote>.
		</emphasis>
		</para>
		<example>
		<title>Set <varname>db_mode</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("db_text", "db_mode", 1)
...
</programlisting>
		</example>
		</section>
	</section>
	<section>
	<title>Exported Functions</title>
		<para>
			<emphasis>None</emphasis>.
	   	</para>
	</section>
	<section>
		<title>Installation and Running</title>
		<para>
		Compile the module and load it instead of mysql or other DB modules.
		</para>
		<para>
		REMINDER: when you use <emphasis>dbtext</emphasis> in &kamailio;,
		the	database URL for modules must be the path to the directory
		where the table-files are located, prefixed by
		<quote>dbtext://</quote>, e.g., 
		<quote>dbtext:///var/dbtext/ser</quote>. If there is no <quote>/</quote>
		after <quote>dbtext://</quote> then <quote>CFG_DIR/</quote> is inserted
		at the beginning of the database path. So, either you provide an
		absolute path to database directory or a relative one to 
		<quote>CFG_DIR</quote> directory.
		</para>
		<example>
		<title>Load the dbtext module</title>
<programlisting format="linespecific">
...
loadmodule "/path/to/kamailio/modules/db_text.so"
...
modparam("module_name", "database_URL", "text:///path/to/dbtext/database")
...
</programlisting>
		</example>
		<section>
			<title>Using dbtext with basic &kamailio; configuration</title>
		<para>
		Here are the definitions for most important table as well as a basic 
		configuration file to use dbtext with &kamailio;. The table structures
		may change in time and you will have to adjust next examples. These are 
		know to work with upcoming &kamailio; v0.9.x
		</para>
		<para>
		You have to populate the table 'subscriber' by hand with user profiles 
		in order to have authentication. To use with the given configuration
		file, the table files must be placed in the '/tmp/serdb' directory.
		</para>
		<example>
		<title>Definition of 'subscriber' table (one line)</title>
<programlisting format="linespecific">
...
username(str) domain(str) password(str) first_name(str) last_name(str) phone(str) email_address(str) datetime_created(int) datetime_modified(int) confirmation(str) flag(str) sendnotification(str) greeting(str) ha1(str) ha1b(str) perms(str) allow_find(str) timezone(str,null) rpid(str,null)
...
</programlisting>
		</example>
		<example>
		<title>Definition of 'location' and 'aliases' tables (one line)</title>
<programlisting format="linespecific">
...
username(str) domain(str,null) contact(str,null) received(str) expires(int,null) q(double,null) callid(str,null) cseq(int,null) last_modified(str) flags(int) user_agent(str) socket(str) 
...
</programlisting>
		</example>
		<example>
		<title>Definition of 'version' table and sample records</title>
<programlisting format="linespecific">
...
table_name(str) table_version(int)
subscriber:3
location:6
aliases:6
...
</programlisting>
		</example>
		<example>
		<title>Configuration file</title>
<programlisting format="linespecific">
...
<xi:include href="db_text.cfg" parse="text"/>
...
</programlisting>
		</example>
		</section>
	</section>
</chapter>