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<?php
/*
* Ties together the batch update components to provide a composable
* method of batch updating rows in a database. To use create a class
* implementing the RowUpdateGenerator interface and configure the
* BatchRowIterator and BatchRowWriter for access to the correct table.
* The components will handle reading, writing, and waiting for replica DBs
* while the generator implementation handles generating update arrays
* for singular rows.
*
* Instantiate:
* $updater = new BatchRowUpdate(
* new BatchRowIterator( $dbr, 'some_table', 'primary_key_column', 500 ),
* new BatchRowWriter( $dbw, 'some_table', 'clusterName' ),
* new MyImplementationOfRowUpdateGenerator
* );
*
* Run:
* $updater->execute();
*
* An example maintenance script utilizing the BatchRowUpdate can be
* located in the Echo extension file maintenance/updateSchema.php
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
* @ingroup Maintenance
*/
class BatchRowUpdate {
/**
* @var BatchRowIterator Iterator that returns an array of
* database rows
*/
protected $reader;
/**
* @var BatchRowWriter Writer capable of pushing row updates
* to the database
*/
protected $writer;
/**
* @var RowUpdateGenerator Generates single row updates
* based on the rows content
*/
protected $generator;
/**
* @var callable Output callback
*/
protected $output;
/**
* @param BatchRowIterator $reader Iterator that returns an
* array of database rows
* @param BatchRowWriter $writer Writer capable of pushing
* row updates to the database
* @param RowUpdateGenerator $generator Generates single row updates
* based on the rows content
*/
public function __construct(
BatchRowIterator $reader, BatchRowWriter $writer, RowUpdateGenerator $generator
) {
$this->reader = $reader;
$this->writer = $writer;
$this->generator = $generator;
$this->output = static function ( $text ) {
}; // nop
}
/**
* Runs the batch update process
*/
public function execute() {
foreach ( $this->reader as $rows ) {
$updates = [];
foreach ( $rows as $row ) {
$update = $this->generator->update( $row );
if ( $update ) {
$updates[] = [
'primaryKey' => $this->reader->extractPrimaryKeys( $row ),
'changes' => $update,
];
}
}
if ( $updates ) {
$this->output( "Processing " . count( $updates ) . " rows\n" );
$this->writer->write( $updates );
}
}
$this->output( "Completed\n" );
}
/**
* Accepts a callable which will receive a single parameter
* containing string status updates
*
* @param callable $output A callback taking a single string
* parameter to output
*/
public function setOutput( callable $output ) {
$this->output = $output;
}
/**
* Write out a status update
*
* @param string $text The value to print
*/
protected function output( $text ) {
call_user_func( $this->output, $text );
}
}
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