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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 out of memory quickly. Also, it
		does not implement 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 db_text 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
		to disk happens at &kamailio; shut down. If db_text is in caching
		mode, many "reload" functions in various modules will not work.
	</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.
				</para>
				<para>
				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>text://</quote>, e.g., 
				<quote>text:///var/dbtext/ser</quote>. If there is no
				<quote>/</quote> after <quote>text://</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>
				<para>
				Do not forget that all databases in &kamailio; needs the <quote>version</quote>
				table.
				</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>
		The first line is the definition of the columns. Each column must be
		declared in the following format:
			<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. If the parameter "emptystring" is
				enabled, db_text sets a NULL string to an empty string 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 does not support 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>
			These 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>
			These 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>Parameters</title>
		<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 the 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>
			<title><varname>emptystring</varname> (integer)</title>
			<para>
			db_text by default handles an empty string as a NULL value.
			Some modules, like the dialplan module, does not accept
			NULL strings. If you enable emptystring an empty string
			will not be NULL, but an empty string.
			</para>

			<para>
			<emphasis>
				Default value is <quote>0</quote> (off).
			</emphasis>
			</para>
			<example>
			<title>Set <varname>emptystring</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("db_text", "emptystring", 1)
...
</programlisting>
			</example>
		</section>
		<section>
			<title><varname>file_buffer_size</varname> (integer)</title>
			<para>
			size of the buffer used to read the text file.
			Some presence tables have columns with large content.
			</para>

			<para>
			<emphasis>
				Default value is <quote>16384</quote> (off).
			</emphasis>
			</para>
			<example>
			<title>Set <varname>file_buffer_size</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("db_text", "file_buffer_size", 8192)
...
</programlisting>
			</example>
		</section>
	</section>
	<section>
	<title>Exported RPC Functions</title>
	<section>
		<title>
		<function moreinfo="none">db_text.dump</function>
		</title>
		<para>Write back to hard drive all modified tables.</para>
		<para>Name: <emphasis>db_text.dump</emphasis></para>
		<para>Parameters: <emphasis>none</emphasis></para>
		<para>RPC Command Format:</para>
		<programlisting  format="linespecific">
	kamcmd db_text.dump
		</programlisting>
	</section>
	</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>text</emphasis> in &kamailio;,
		the	database URL for modules must be the path to the directory
		where the table-files are located, prefixed by
		<quote>text://</quote>, e.g., 
		<quote>text:///var/dbtext/ser</quote>. If there is no <quote>/</quote>
		after <quote>text://</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_k/db_text.so"
...
modparam("module_name", "db_url", "text:///path/to/dbtext/database")
...
</programlisting>
		</example>
		<section>
			<title>Using db_text with a basic &kamailio; configuration</title>
		<para>
		Here are definitions for the most important tables as well as a basic 
		configuration file to use db_text with &kamailio;. The table structures
		may change in time and you will have to adjust these examples. Check the
		source code directory <quote>utils/kamctl/dbtxt/kamailio</quote> for
		current definitions.
		</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>

