# &adminguide;

## Overview

The module implements a simplified database engine based on text files. It can be used by &osips; DB interface instead of other database module (like MySQL).

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 with &osips;

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).

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 OpenSIPS shut down.

### Design of db_text engine

The db_text database system architecture:

- a database is represented by a directory in the local file system. NOTE: when you use db_text in &osips;, the database URL for modules must be the path to the directory where the table-files are located, prefixed by text://, e.g., text:///var/dbtext/opensips. If there is no / after text:// then CFG_DIR/ is inserted at the beginning of the database path. So, either you provide an absolute path to database directory or a relative one to CFG_DIR directory.

- a table is represented by a text file inside database directory.

### Internal format of a db_text table

First line is the definition of the columns. Each column must be declared as follows:

- the name of column must not include white spaces.

- the format of a column definition is: name(type,attr).

- between two column definitions must be a white space, e.g., first_name(str) last_name(str).

- the type of a column can be:

  - int - integer numbers.

  - double - real numbers with two decimals.

  - str - strings with maximum size of 4KB.

- a column can have one of the attributes:

  - auto - only for 'int' columns, the maximum value in that column is incremented and stored in this field if it is not provided in queries.

  - null - accept null values in column fields.

  - if no attribute is set, the fields of the column cannot have null value.

- each other line is a row with data. The line ends with \n.

- the fields are separated by :.

- no value between two ':' (or between ':' and start/end of a row) means null value.

- next characters must be escaped in strings: \n, \r, \t, :.

- 0 -- the zero value must be escaped too.

#### Sample of a db_text table

    ...
    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:
    ...

#### Minimal &osips; location db_text table definition

    ...
    username(str) contact(str) expires(int) q(double) callid(str) cseq(int)
    ...

#### Minimal &osips; subscriber db_text table example

    ...
    username(str) password(str) ha1(str) domain(str) ha1b(str)
    suser:supasswd:xxx:alpha.org:xxx
    ...

### Existing limitations

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.

## Dependencies

### &osips; modules

The next modules must be loaded before this module:

- none.

### External libraries or applications

The next libraries or applications must be installed before running &osips; with this module:

- none.

## Exported Parameters

None.

### `db_mode` (integer)

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.

Default value is 0.

#### Set `db_mode` parameter

    ...
    modparam("db_text", "db_mode", 1)
    ...

## Exported Functions

None.

## Exported MI Functions

### `dbt_dump`

Write back to hard drive modified tables.

Name: dbt_dump.

Parameters: none

MI FIFO Command Format:

    :dbt_dump:_reply_fifo_file_
    _empty_line_

### `dbt_reload`

Causes db_text module to reload cached tables from disk. Depending on parameters it could be a whole cache or a specified database or a single table. If any table cannot be reloaded from disk - the old version preserved and error reported.

Name: dbt_reload.

Parameters:

- db_name (optional) - database name to reload.

- table_name (optional, but cannot be present without the db_name parameter) - specific table to reload.

MI FIFO Command Format:

    :dbt_reload:_reply_fifo_file_
    _empty_line_

    :dbt_reload:_reply_fifo_file_
    /path/to/dbtext/database
    _empty_line_

    :dbt_reload:_reply_fifo_file_
    /path/to/dbtext/database
    table_name
    _empty_line_

## Installation and Running

Compile the module and load it instead of mysql or other DB modules.

REMINDER: when you use db_text in &osips;, the database URL for modules must be the path to the directory where the table-files are located, prefixed by text://, e.g., text:///var/dbtext/opensips. If there is no / after text:// then CFG_DIR/ is inserted at the beginning of the database path. So, either you provide an absolute path to database directory or a relative one to CFG_DIR directory.

### Load the db_text module

    ...
    loadmodule "/path/to/opensips/modules/db_text.so"
    ...
    modparam("module_name", "database_URL", "text:///path/to/dbtext/database")
    ...

### Using db_text with basic &osips; configuration

Here are the definitions for most important table as well as a basic configuration file to use db_text with &osips;. The table structures may change in time and you will have to adjust next examples.

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/opensipsdb' directory.

#### Definition of 'subscriber' table (one line)

    ...
    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)
    ...

#### Definition of 'location' and 'aliases' tables (one line)

    ...
    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)
    ...

#### Definition of 'version' table and sample records

    ...
    table_name(str) table_version(int)
    subscriber:3
    location:6
    aliases:6
    ...

#### Configuration file

    ...
    &dbtextsercfg;
    ...