https://bugzilla.wikimedia.org/show_bug.cgi?id=17221
Summary: Feature Req: Database class does not provide support for
database Aliases
Product: MediaWiki
Version: 1.13.2
Platform: All
OS/Version: All
Status: NEW
Keywords: patch
Severity: enhancement
Priority: Normal
Component: Database
AssignedTo: [email protected]
ReportedBy: [email protected]
Created an attachment (id=5743)
--> (https://bugzilla.wikimedia.org/attachment.cgi?id=5743)
Diff file of Database.php
The existing abstraction layers provided in the Database.php class do not
provide full support for database aliases.
Use Case:
A developer wishes to create an extension or other project that requires
additional database tables. The developers database design preference is to use
the same field name where there are relations between tables, e.g.
########### ########### ###########
# foo # # foo_bar # # bar #
########### ########### ###########
# foo_id # # foo_id # # bar_id #
# foo_name# # bar_id # # bar_name#
########### ########### ###########
If creating a SQL query utilising a join the developer would use aliases and
write:
SELECT f.foo_name, b.bar_name FROM foo AS f LEFT JOIN foo_bar AS j ON f.foo_id
= j.foo_id LEFT JOIN bar AS b ON j.bar_id = b.bar_id WHERE b.bar_id = 8;
The developer wishes to use the API provided by the Database class in MediaWiki
to maintain code portability and so creates the following code:
$table = array("foo AS f", "foo_bar AS j", "bar AS b");
$vars = array("f.foo_name", "b.bar_name");
$conds = "b.bar_id = {$criteria}";
$options = "";
$join = array("foo_bar" => array("LEFT JOIN", "f.foo_id = j.foo_id"), "bar" =>
array("LEFT JOIN", "j.bar_id = b.bar_id"));
$dbQuery = $dbSlave->select($table, $vars, $conds, "myFunction", $options,
$join);
As the table names are parsed through Database::tableName() they will encounter
the rule on line 01467 which will return the table name without adding the
$wgSharedPrefix value, resuling in a "Table does not exist" database error.
This may be worked around by using:
$vars = array("{$dbSlave->tableName("foo")}.foo_name",
"{$dbSlave->tableName("bar")}.bar_name");
$join = array("foo_bar" => array("LEFT JOIN",
"{$dbSlave->tableName("foo")}.foo_id =
{$dbSlave->tableName("foo_bar")}.foo_id"), "bar" => array("LEFT JOIN",
"{$dbSlave->tableName("foo_bar")}.bar_id =
{$dbSlave->tableName("bar")}.bar_id"));
However as the developer's code grows and more joins are required, the code
grows larger and uglier.
Suggested solution:
Attached is a diff file of my changes to Database.php which addresses this
issue. Aliases can now be created on Select statements by creating a 2
dimensional array in the $table variable as so:
$table = array(array("foo", f"), array("foo_bar", "j"), array("bar", "b"));
$vars = array("f.foo_name", "b.bar_name");
$conds = "b.bar_id = {$criteria}";
$options = "";
$join = array("foo_bar" => array("LEFT JOIN", "f.foo_id = j.foo_id"), "bar" =>
array("LEFT JOIN", "j.bar_id = b.bar_id"));
$dbQuery = $dbSlave->select($table, $vars, $conds, "myFunction", $options,
$join);
Queries that do not utilise aliases can still be performed using the previous
methods and should not break existing usage cases.
--
Configure bugmail: https://bugzilla.wikimedia.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.
You are on the CC list for the bug.
_______________________________________________
Wikibugs-l mailing list
[email protected]
https://lists.wikimedia.org/mailman/listinfo/wikibugs-l
