# &adminguide;

## Overview

ALIAS_DB module can be used as an alternative for user aliases via usrloc. The main feature is that it does not store all adjacent data as for user location and always uses database for search (no memory caching).

Having no memory caching, search speed might decrease but provisioning is easier. With very fast databases like MySQL, speed penalty can be lowered. Also, search can be performed on different tables in the same script.

## Dependencies

### &osips; Modules

The following modules must be loaded before this module:

- database module (mysql, dbtext, ...).

### External Libraries or Applications

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

- None.

## Exported Parameters

### `db_url` (str)

Database URL.

Default value is &defaultrodb;.

#### Set `db_url` parameter

    ...
    modparam("alias_db", "db_url", "&exampledb;")
    ...

### `user_column` (str)

Name of the column storing username.

Default value is username.

#### Set `user_column` parameter

    ...
    modparam("alias_db", "user_column", "susername")
    ...

### `domain_column` (str)

Name of the column storing user's domain.

Default value is domain.

#### Set `domain_column` parameter

    ...
    modparam("alias_db", "domain_column", "sdomain")
    ...

### `alias_user_column` (str)

Name of the column storing alias username.

Default value is alias_username.

#### Set `alias_user_column` parameter

    ...
    modparam("alias_db", "alias_user_column", "auser")
    ...

### `alias_domain_column` (str)

Name of the column storing alias domain.

Default value is alias_domain.

#### Set `alias_domain_column` parameter

    ...
    modparam("alias_db", "alias_domain_column", "adomain")
    ...

### `domain_prefix` (str)

Specifies the prefix to be stripped from the domain in R-URI before doing the search.

Default value is NULL.

#### Set `domain_prefix` parameter

    ...
    modparam("alias_db", "domain_prefix", "sip.")
    ...

### `append_branches` (int)

If the alias resolves to many SIP IDs, the first is replacing the R-URI, the rest are added as branches.

Default value is 0 (0 - don't add branches; 1 - add branches).

#### Set `append_branches` parameter

    ...
    modparam("alias_db", "append_branches", 1)
    ...

## Exported Functions

### `alias_db_lookup( table_name [,flags] )`

The function takes the R-URI and search to see whether it is an alias or not. If it is an alias for a local user, the R-URI is replaced with user's SIP uri.

The function returns TRUE if R-URI is alias and it was replaced by user's SIP uri.

Meaning of the parameters is as follows:

- table_name - any PV (string or PV or mix) the name of the table where to search for alias.

- flags (optional) - set of flags (char based flags) to control the alias lookup process:

  - d - do not use domain URI part in the alias lookup query (use only a username-based lookup). By default, both username and domain are used.

  - r - do revers alias lookup - lookup for the alias mapped to the current URI (URI 2 alias translation); normally, the function looks up for the URI mapped to the alias (alias 2 URI translation).

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

#### `alias_db_lookup()` usage

    ...
    alias_db_lookup("dbaliases" , "rd");
    alias_db_lookup("dba_$(rU{s.substr,0,1})");
    ...

### `alias_db_find( table_name , input, output [,flags] )`

The function is very similar to `alias_db_lookup()`, but instead of using fixed input (RURI) and output (RURI) is able to get the input SIP URI from a pseudo-variable and place the result back also in a pseudo-variable.

The function is useful as the alias lookup does not affect the request itself (no RURI changes), can be used in a reply context (as it does not work with RURI only) and can be used for others URI than the RURI (To URI, From URI, custom URI).

The function returns TRUE if any alias mapping was found and returned.

Meaning of the parameters is as follows:

- table_name - any PV (string or PV or mix) the name of the table where to search for alias.

- input - any PV (string or PV or mix) carrying the SIP URI that needs to be looked up.

- output - PV (AVP or script VAR) where to place the SIP URI resulting from the alias lookup.

- flags (optional) - set of flags (char based flags) to control the alias lookup process:

  - d - do not use domain URI part in the alias lookup query (use only a username-based lookup). By default, both username and domain are used.

  - r - do revers alias lookup - lookup for the alias mapped to the current URI (URI 2 alias translation); normally, the function looks up for the URI mapped to the alias (alias 2 URI translation).

This function can be used from REQUEST_ROUTE, BRANCH_ROUTE, LOCAL_ROUTE, STARTUP_ROUTE, FAILURE_ROUTE and ONREPLY_ROUTE.

#### `alias_db_find()` usage

    ...
    # do revers alias lookup and find the alias for the FROM URI
    alias_db_find("dbaliases" , "$fu", "$avp(from_alias)", "r");
    ...