====== MantisBT Database Schema ======

This pages documents the MantisBT schema definition script (//admin/schema.php//), and explains how to modify it.

===== Introduction =====

The schema is defined as a numbered list of updates (aka //upgrade steps//), stored as an array. Each step consists of two elements:

  - A **function** to generate SQL statements. Available operations are described in [[#upgrade_functions|Upgrade Functions section]] below
  - An array of **parameters** to be passed to the function.

<WRAP important round>
**The schema's integrity relies on strict ordering of this array.**

  * ONLY ADD NEW CHANGES TO THE END OF THE TABLE!!!\\ Always specify the schema step (array key), for documentation purposes
  * NEVER SKIP AN INDEX IN THE SEQUENCE!!!
</WRAP>

//Release markers// are placed right AFTER the last schema step that is included in the corresponding release:

<code php>
$g_upgrade[173] = array( 'AddColumnSQL', array( db_get_table( 'bug_file' ), "
	user_id					I		UNSIGNED NOTNULL DEFAULT '0' " ) );

# Release marker: 1.2.0rc1

$g_upgrade[174] = array( 'DropColumnSQL', array( db_get_table( 'custom_field' ), 'advanced' ) );
</code>

In the above example, steps up to 173 are part of 1.2.0rc1, while 174 and onwards are included in 1.2.0rc2.

===== Upgrade functions =====

This section documents available upgrade operations:

  * Data dictionary operations from ADOdb library; one of: 
    * Tables: ''CreateTableSQL'', ''ChangeTableSQL'', ''RenameTableSQL'', ''DropTableSQL'',
    * Columns: ''AddColumnSQL'', ''AlterColumnSQL'', ''RenameColumnSQL'', ''DropColumnSQL'',
    * Indexes: ''CreateIndexSQL'', ''DropIndexSQL''
  * ''InsertData''
  * ''UpdateFunction'': local function to perform arbitrary changes
  * ''null'': no-op upgrade step

==== CreateTableSQL ====
==== ChangeTableSQL ====
==== RenameTableSQL ====
==== DropTableSQL ====
==== AddColumnSQL ====
==== AlterColumnSQL ====
==== RenameColumnSQL ====
==== DropColumnSQL ====
==== CreateIndexSQL ====
==== DropIndexSQL ====
==== InsertData ====

Local function to add data to a table.

==== UpdateFunction ====

''UpdateFunction'' allows arbitrary PHP code to be executed via a function, which must be defined in //install_helper_functions_api.php// with an ''install_'' prefix.

Example 1: Simple function without arguments

  * schema.php <code php>
$g_upgrade[186] = array( 'UpdateFunction', 'update_history_long_custom_fields' );
</code>
  * install_helper_functions_api.php <code php>
function install_update_history_long_custom_fields() {
	# [... function code ...]
}
</code>

Example 2: function with arguments

  * schema.php (actual code was reformatted to improve readability)<code php>
$g_upgrade[107] = array( 'UpdateFunction', 'date_migrate', array(
	db_get_table( 'bug_file' ),
	'id',
	'date_added',
	'date_added_int'
) );
</code>
  * install_helper_functions_api.php <code php>
/**
 * Migrate the legacy date format.
 * @param array $p_data Array: [0] = tablename, [1] id column, [2] = old column, [3] = new column.
 * @return integer
 */
function install_date_migrate( array $p_data ) {
	# [... function code ...]
}
</code>

==== null ====

No-op upgrade step. The installer will do nothing.

This is used to skip the step while maintaining the upgrade sequence, e.g. when an operation becomes obsolete or doesn't apply for specific cases.