Daniel-Constantin
Mierla
FhG FOKUS

    		mierla@fokus.fraunhofer.de

2003
2004
FhG FOKUS
$Revision: 1.3 $
$Date: 2005/08/24 22:26:17 $

# Dbtext Module

## Overview

The module implements a simplified database engine based on text files. It can be used by SER 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 (who knows ?!?) with SER.

### Design of Dbtext Engine

The dbtext database system architecture:

- A database is represented by a directory on the local file system.

  When you use "dbtext" in SER, the database URL for modules must be the path to the directory where the table-files are located, prefixed by "dbtext://", e.g., "dbtext:///var/dbtext/ser". If there is no "/" after "dbtext://" 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 Dbtext 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 dbtext table

    ...
    id(int,auto) name(str) flag(double) desc(str,null)
    1:nick:0.34:a\tgood\:friend
    2:cole:-3.75:colleague3:bob:2.50:
    ...

#### Minimal SER location dbtext table definition

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

#### Minimal SER subscriber dbtext table example

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

## Installation And Running

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

When you use dbtext in SER, the database URL for modules must be the path to the directory where the table-files are located, prefixed by "dbtext://", e.g., "dbtext:///var/dbtext/ser". If there is no "/" after "dbtext://" 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 dbtext module

    ...
    loadmodule "/path/to/ser/modules/dbtext.so"
    ...
    modparam("module_name", "db_url", "dbtext:///path/to/dbtext/database")
    ...

### Using Dbtext With Basic SER Configuration

Here are the definitions for most important table as well as a basic configuration file to use dbtext with SER. 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/serdb' directory.

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

    ...
    username(str) domn(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)
    uuid(str,null)
    ...

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

    ...
    username(str) domain(str,null) contact(str,null) expires(int,null)
    q(double,null) callid(str,null) cseq(int,null)
    last_modified(str) replicate(int,null) state(int,null)
    flags(int) user_agent(str) received(str)
    ...

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

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

#### Configuration file