Import BatchRowUpdate classes from Echo
authorErik Bernhardson <ebernhardson@wikimedia.org>
Thu, 30 Jul 2015 22:09:11 +0000 (15:09 -0700)
committerMatthew Flaschen <mflaschen@wikimedia.org>
Fri, 14 Aug 2015 01:28:13 +0000 (21:28 -0400)
This is a set of classes written for Echo to simplify writing
maintenance scripts that iterate over an entire table and update
some of those rows.

This has shown to be reusable elsewhere, especially the BatchRowIterator
class and will be useful to have generally avilable in core. The Echo
classes are all prefixed with the Echo name so there wont be any
conflict is both are installed.

Change-Id: I64c1751106caf34f41af799dbaf8794115537f06

autoload.php
includes/utils/BatchRowIterator.php [new file with mode: 0644]
includes/utils/BatchRowUpdate.php [new file with mode: 0644]
includes/utils/BatchRowWriter.php [new file with mode: 0644]
includes/utils/RowUpdateGenerator.php [new file with mode: 0644]
includes/utils/iterators/IteratorDecorator.php [new file with mode: 0644]
includes/utils/iterators/NotRecursiveIterator.php [new file with mode: 0644]
tests/phpunit/includes/utils/BatchRowUpdateTest.php [new file with mode: 0644]

index a8940c4..d257721 100644 (file)
@@ -157,6 +157,9 @@ $wgAutoloadLocalClasses = array(
        'BagOStuff' => __DIR__ . '/includes/libs/objectcache/BagOStuff.php',
        'BaseDump' => __DIR__ . '/maintenance/backupPrefetch.inc',
        'BaseTemplate' => __DIR__ . '/includes/skins/BaseTemplate.php',
+       'BatchRowIterator' => __DIR__ . '/includes/utils/BatchRowIterator.php',
+       'BatchRowUpdate' => __DIR__ . '/includes/utils/BatchRowUpdate.php',
+       'BatchRowWriter' => __DIR__ . '/includes/utils/BatchRowWriter.php',
        'BatchedQueryRunner' => __DIR__ . '/maintenance/runBatchedQuery.php',
        'BcryptPassword' => __DIR__ . '/includes/password/BcryptPassword.php',
        'BenchHttpHttps' => __DIR__ . '/maintenance/benchmarks/bench_HTTP_HTTPS.php',
@@ -572,6 +575,7 @@ $wgAutoloadLocalClasses = array(
        'InstallerOverrides' => __DIR__ . '/mw-config/overrides.php',
        'Interwiki' => __DIR__ . '/includes/interwiki/Interwiki.php',
        'InvalidPassword' => __DIR__ . '/includes/password/InvalidPassword.php',
+       'IteratorDecorator' => __DIR__ . '/includes/utils/iterators/IteratorDecorator.php',
        'IuConverter' => __DIR__ . '/languages/classes/LanguageIu.php',
        'JSCompilerContext' => __DIR__ . '/includes/libs/jsminplus.php',
        'JSMinPlus' => __DIR__ . '/includes/libs/jsminplus.php',
@@ -814,6 +818,7 @@ $wgAutoloadLocalClasses = array(
        'NewPagesPager' => __DIR__ . '/includes/specials/SpecialNewpages.php',
        'NewUsersLogFormatter' => __DIR__ . '/includes/logging/NewUsersLogFormatter.php',
        'NolinesImageGallery' => __DIR__ . '/includes/gallery/NolinesImageGallery.php',
+       'NotRecursiveIterator' => __DIR__ . '/includes/utils/iterators/NotRecursiveIterator.php',
        'NukeNS' => __DIR__ . '/maintenance/nukeNS.php',
        'NukePage' => __DIR__ . '/maintenance/nukePage.php',
        'NullFileJournal' => __DIR__ . '/includes/filebackend/filejournal/FileJournal.php',
@@ -1051,6 +1056,7 @@ $wgAutoloadLocalClasses = array(
        'RightsLogFormatter' => __DIR__ . '/includes/logging/RightsLogFormatter.php',
        'RollbackAction' => __DIR__ . '/includes/actions/RollbackAction.php',
        'RollbackEdits' => __DIR__ . '/maintenance/rollbackEdits.php',
+       'RowUpdateGenerator' => __DIR__ . '/includes/utils/RowUpdateGenerator.php',
        'RunJobs' => __DIR__ . '/maintenance/runJobs.php',
        'RunningStat' => __DIR__ . '/includes/libs/RunningStat.php',
        'SQLiteField' => __DIR__ . '/includes/db/DatabaseSqlite.php',
diff --git a/includes/utils/BatchRowIterator.php b/includes/utils/BatchRowIterator.php
new file mode 100644 (file)
index 0000000..9441608
--- /dev/null
@@ -0,0 +1,278 @@
+<?php
+/**
+ * Allows iterating a large number of rows in batches transparently.
+ * By default when iterated over returns the full query result as an
+ * array of rows.  Can be wrapped in RecursiveIteratorIterator to
+ * collapse those arrays into a single stream of rows queried in batches.
+ *
+ * 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 BatchRowIterator implements RecursiveIterator {
+
+       /**
+        * @var DatabaseBase $db The database to read from
+        */
+       protected $db;
+
+       /**
+        * @var string $table The name of the table to read from
+        */
+       protected $table;
+
+       /**
+        * @var array $primaryKey The name of the primary key(s)
+        */
+       protected $primaryKey;
+
+       /**
+        * @var integer $batchSize The number of rows to fetch per iteration
+        */
+       protected $batchSize;
+
+       /**
+        * @var array $conditions Array of strings containing SQL conditions
+        *  to add to the query
+        */
+       protected $conditions = array();
+
+       /**
+        * @var array $joinConditions
+        */
+       protected $joinConditions = array();
+
+       /**
+        * @var array $fetchColumns List of column names to select from the
+        *  table suitable for use with DatabaseBase::select()
+        */
+       protected $fetchColumns;
+
+       /**
+        * @var string $orderBy SQL Order by condition generated from $this->primaryKey
+        */
+       protected $orderBy;
+
+       /**
+        * @var array $current The current iterator value
+        */
+       private $current = array();
+
+       /**
+        * @var integer key 0-indexed number of pages fetched since self::reset()
+        */
+       private $key;
+
+       /**
+        * @param DatabaseBase $db         The database to read from
+        * @param string       $table      The name of the table to read from
+        * @param string|array $primaryKey The name or names of the primary key columns
+        * @param integer      $batchSize  The number of rows to fetch per iteration
+        * @throws MWException
+        */
+       public function __construct( DatabaseBase $db, $table, $primaryKey, $batchSize ) {
+               if ( $batchSize < 1 ) {
+                       throw new MWException( 'Batch size must be at least 1 row.' );
+               }
+               $this->db = $db;
+               $this->table = $table;
+               $this->primaryKey = (array) $primaryKey;
+               $this->fetchColumns = $this->primaryKey;
+               $this->orderBy = implode( ' ASC,', $this->primaryKey ) . ' ASC';
+               $this->batchSize = $batchSize;
+       }
+
+       /**
+        * @param array $condition Query conditions suitable for use with
+        *  DatabaseBase::select
+        */
+       public function addConditions( array $conditions ) {
+               $this->conditions = array_merge( $this->conditions, $conditions );
+       }
+
+       /**
+        * @param array $condition Query join conditions suitable for use
+        *  with DatabaseBase::select
+        */
+       public function addJoinConditions( array $conditions ) {
+               $this->joinConditions = array_merge( $this->joinConditions, $conditions );
+       }
+
+       /**
+        * @param array $columns List of column names to select from the
+        *  table suitable for use with DatabaseBase::select()
+        */
+       public function setFetchColumns( array $columns ) {
+               // If it's not the all column selector merge in the primary keys we need
+               if ( count( $columns ) === 1 && reset( $columns ) === '*' ) {
+                       $this->fetchColumns = $columns;
+               } else {
+                       $this->fetchColumns = array_unique( array_merge(
+                               $this->primaryKey,
+                               $columns
+                       ) );
+               }
+       }
+
+       /**
+        * Extracts the primary key(s) from a database row.
+        *
+        * @param stdClass $row An individual database row from this iterator
+        * @return array Map of primary key column to value within the row
+        */
+       public function extractPrimaryKeys( $row ) {
+               $pk = array();
+               foreach ( $this->primaryKey as $column ) {
+                       $pk[$column] = $row->$column;
+               }
+               return $pk;
+       }
+
+       /**
+        * @return array The most recently fetched set of rows from the database
+        */
+       public function current() {
+               return $this->current;
+       }
+
+       /**
+        * @return integer 0-indexed count of the page number fetched
+        */
+       public function key() {
+               return $this->key;
+       }
+
+       /**
+        * Reset the iterator to the begining of the table.
+        */
+       public function rewind() {
+               $this->key = -1; // self::next() will turn this into 0
+               $this->current = array();
+               $this->next();
+       }
+
+       /**
+        * @return boolean True when the iterator is in a valid state
+        */
+       public function valid() {
+               return (bool) $this->current;
+       }
+
+       /**
+        * @return boolean True when this result set has rows
+        */
+       public function hasChildren() {
+               return $this->current && count( $this->current );
+       }
+
+       /**
+        * @return RecursiveIterator
+        */
+       public function getChildren() {
+               return new NotRecursiveIterator( new ArrayIterator( $this->current ) );
+       }
+
+       /**
+        * Fetch the next set of rows from the database.
+        */
+       public function next() {
+               $res = $this->db->select(
+                       $this->table,
+                       $this->fetchColumns,
+                       $this->buildConditions(),
+                       __METHOD__,
+                       array(
+                               'LIMIT' => $this->batchSize,
+                               'ORDER BY' => $this->orderBy,
+                       ),
+                       $this->joinConditions
+               );
+
+               // The iterator is converted to an array because in addition to
+               // returning it in self::current() we need to use the end value
+               // in self::buildConditions()
+               $this->current = iterator_to_array( $res );
+               $this->key++;
+       }
+
+       /**
+        * Uses the primary key list and the maximal result row from the
+        * previous iteration to build an SQL condition sufficient for
+        * selecting the next page of results.  All except the final key use
+        * `=` conditions while the final key uses a `>` condition
+        *
+        * Example output:
+        *        array( '( foo = 42 AND bar > 7 ) OR ( foo > 42 )' )
+        *
+        * @return array The SQL conditions necessary to select the next set
+        *  of rows in the batched query
+        */
+       protected function buildConditions() {
+               if ( !$this->current ) {
+                       return $this->conditions;
+               }
+
+               $maxRow = end( $this->current );
+               $maximumValues = array();
+               foreach ( $this->primaryKey as $column ) {
+                       $maximumValues[$column] = $this->db->addQuotes( $maxRow->$column );
+               }
+
+               $pkConditions = array();
+               // For example: If we have 3 primary keys
+               // first run through will generate
+               //   col1 = 4 AND col2 = 7 AND col3 > 1
+               // second run through will generate
+               //   col1 = 4 AND col2 > 7
+               // and the final run through will generate
+               //   col1 > 4
+               while ( $maximumValues ) {
+                       $pkConditions[] = $this->buildGreaterThanCondition( $maximumValues );
+                       array_pop( $maximumValues );
+               }
+
+               $conditions = $this->conditions;
+               $conditions[] = sprintf( '( %s )', implode( ' ) OR ( ', $pkConditions ) );
+
+               return $conditions;
+       }
+
+       /**
+        * Given an array of column names and their maximum value  generate
+        * an SQL condition where all keys except the last match $quotedMaximumValues
+        * exactly and the last column is greater than the matching value in
+        * $quotedMaximumValues
+        *
+        * @param array $quotedMaximumValues The maximum values quoted with
+        *  $this->db->addQuotes()
+        * @return string An SQL condition that will select rows where all
+        *  columns match the maximum value exactly except the last column
+        *  which must be greater than the provided maximum value
+        */
+       protected function buildGreaterThanCondition( array $quotedMaximumValues ) {
+               $keys = array_keys( $quotedMaximumValues );
+               $lastColumn = end( $keys );
+               $lastValue = array_pop( $quotedMaximumValues );
+               $conditions = array();
+               foreach ( $quotedMaximumValues as $column => $value ) {
+                       $conditions[] = "$column = $value";
+               }
+               $conditions[] = "$lastColumn > $lastValue";
+
+               return implode( ' AND ', $conditions );
+       }
+}
diff --git a/includes/utils/BatchRowUpdate.php b/includes/utils/BatchRowUpdate.php
new file mode 100644 (file)
index 0000000..a4257a5
--- /dev/null
@@ -0,0 +1,133 @@
+<?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 slaves
+ * 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 $reader Iterator that returns an array of
+        *  database rows
+        */
+       protected $reader;
+
+       /**
+        * @var BatchRowWriter $writer Writer capable of pushing row updates
+        *  to the database
+        */
+       protected $writer;
+
+       /**
+        * @var RowUpdateGenerator $generator Generates single row updates
+        *  based on the rows content
+        */
+       protected $generator;
+
+       /**
+        * @var callable $output 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 = function() {
+               }; // nop
+       }
+
+       /**
+        * Runs the batch update process
+        */
+       public function execute() {
+               foreach ( $this->reader as $rows ) {
+                       $updates = array();
+                       foreach ( $rows as $row ) {
+                               $update = $this->generator->update( $row );
+                               if ( $update ) {
+                                       $updates[] = array(
+                                               '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
+        *
+        * @throws MWException
+        */
+       public function setOutput( $output ) {
+               if ( !is_callable( $output ) ) {
+                       throw new MWException(
+                               'Provided $output param is required to be callable.'
+                       );
+               }
+               $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 );
+       }
+}
diff --git a/includes/utils/BatchRowWriter.php b/includes/utils/BatchRowWriter.php
new file mode 100644 (file)
index 0000000..9daeab1
--- /dev/null
@@ -0,0 +1,71 @@
+<?php
+/**
+ * Updates database rows by primary key in batches.
+ *
+ * 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 BatchRowWriter {
+       /**
+        * @var DatabaseBase $db The database to write to
+        */
+       protected $db;
+
+       /**
+        * @var string $table The name of the table to update
+        */
+       protected $table;
+
+       /**
+        * @var string $clusterName A cluster name valid for use with LBFactory
+        */
+       protected $clusterName;
+
+       /**
+        * @param DatabaseBase $db          The database to write to
+        * @param string       $table       The name of the table to update
+        * @param string|bool  $clusterName A cluster name valid for use with LBFactory
+        */
+       public function __construct( DatabaseBase $db, $table, $clusterName = false ) {
+               $this->db = $db;
+               $this->table = $table;
+               $this->clusterName = $clusterName;
+       }
+
+       /**
+        * @param array $updates Array of arrays each containing two keys, 'primaryKey'
+     *  and 'changes'. primaryKey must contain a map of column names to values
+        *  sufficient to uniquely identify the row changes must contain a map of column
+        *  names to update values to apply to the row.
+        */
+       public function write( array $updates ) {
+               $this->db->begin();
+
+               foreach ( $updates as $update ) {
+                       $this->db->update(
+                               $this->table,
+                               $update['changes'],
+                               $update['primaryKey'],
+                               __METHOD__
+                       );
+               }
+
+               $this->db->commit();
+               wfWaitForSlaves( false, false, $this->clusterName );
+       }
+}
diff --git a/includes/utils/RowUpdateGenerator.php b/includes/utils/RowUpdateGenerator.php
new file mode 100644 (file)
index 0000000..6a4792c
--- /dev/null
@@ -0,0 +1,39 @@
+<?php
+/**
+ * Interface for generating updates to single rows in the database.
+ *
+ * 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
+ */
+interface RowUpdateGenerator {
+       /**
+        * Given a database row, generates an array mapping column names to
+        * updated value within the database row.
+        *
+        * Sample Response:
+        *   return array(
+        *       'some_col' => 'new value',
+        *       'other_col' => 99,
+        *   );
+        *
+        * @param stdClass $row A row from the database
+        * @return array Map of column names to updated value within the
+        *  database row. When no update is required returns an empty array.
+        */
+       public function update( $row );
+}
diff --git a/includes/utils/iterators/IteratorDecorator.php b/includes/utils/iterators/IteratorDecorator.php
new file mode 100644 (file)
index 0000000..288a311
--- /dev/null
@@ -0,0 +1,50 @@
+<?php
+/**
+ * Allows extending classes to decorate an Iterator with
+ * reduced boilerplate.
+ *
+ * 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
+ */
+abstract class IteratorDecorator implements Iterator {
+       protected $iterator;
+
+       public function __construct( Iterator $iterator ) {
+               $this->iterator = $iterator;
+       }
+
+       public function current() {
+               return $this->iterator->current();
+       }
+
+       public function key() {
+               return $this->iterator->key();
+       }
+
+       public function next() {
+               return $this->iterator->next();
+       }
+
+       public function rewind() {
+               return $this->iterator->rewind();
+       }
+
+       public function valid() {
+               return $this->iterator->valid();
+       }
+}
diff --git a/includes/utils/iterators/NotRecursiveIterator.php b/includes/utils/iterators/NotRecursiveIterator.php
new file mode 100644 (file)
index 0000000..52ca61b
--- /dev/null
@@ -0,0 +1,35 @@
+<?php
+/**
+ * Wraps a non-recursive iterator with methods to be recursive
+ * without children.
+ *
+ * Alternatively wraps a recursive iterator to prevent recursing deeper
+ * than the wrapped iterator.
+ *
+ * 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 NotRecursiveIterator extends IteratorDecorator implements RecursiveIterator {
+       public function hasChildren() {
+               return false;
+       }
+
+       public function getChildren() {
+               return null;
+       }
+}
diff --git a/tests/phpunit/includes/utils/BatchRowUpdateTest.php b/tests/phpunit/includes/utils/BatchRowUpdateTest.php
new file mode 100644 (file)
index 0000000..a2b35f3
--- /dev/null
@@ -0,0 +1,243 @@
+<?php
+
+/**
+ * Tests for BatchRowUpdate and its components
+ *
+ * @group db
+ */
+class BatchRowUpdateTest extends MediaWikiTestCase {
+
+       public function testWriterBasicFunctionality() {
+               $db = $this->mockDb();
+               $writer = new BatchRowWriter( $db, 'echo_event' );
+
+               $updates = array(
+                       self::mockUpdate( array( 'something' => 'changed' ) ),
+                       self::mockUpdate( array( 'otherthing' => 'changed' ) ),
+                       self::mockUpdate( array( 'and' => 'something', 'else' => 'changed' ) ),
+               );
+
+               $db->expects( $this->exactly( count( $updates ) ) )
+                       ->method( 'update' );
+
+               $writer->write( $updates );
+       }
+
+       static protected function mockUpdate( array $changes ) {
+               static $i = 0;
+               return array(
+                       'primaryKey' => array( 'event_id' => $i++ ),
+                       'changes' => $changes,
+               );
+       }
+
+       public function testReaderBasicIterate() {
+               $db = $this->mockDb();
+               $batchSize = 2;
+               $reader = new BatchRowIterator( $db, 'some_table', 'id_field', $batchSize );
+
+               $response = $this->genSelectResult( $batchSize, /*numRows*/ 5, function() {
+                       static $i = 0;
+                       return array( 'id_field' => ++$i );
+               } );
+               $db->expects( $this->exactly( count( $response ) ) )
+                       ->method( 'select' )
+                       ->will( $this->consecutivelyReturnFromSelect( $response ) );
+
+               $pos = 0;
+               foreach ( $reader as $rows ) {
+                       $this->assertEquals( $response[$pos], $rows, "Testing row in position $pos" );
+                       $pos++;
+               }
+               // -1 is because the final array() marks the end and isnt included
+               $this->assertEquals( count( $response ) - 1, $pos );
+       }
+
+       static public function provider_readerGetPrimaryKey() {
+               $row = array(
+                       'id_field' => 42,
+                       'some_col' => 'dvorak',
+                       'other_col' => 'samurai',
+               );
+               return array(
+
+                       array(
+                               'Must return single column pk when requested',
+                               array( 'id_field' => 42 ),
+                               $row
+                       ),
+
+                       array(
+                               'Must return multiple column pks when requested',
+                               array( 'id_field' => 42, 'other_col' => 'samurai' ),
+                               $row
+                       ),
+
+               );
+       }
+
+       /**
+        * @dataProvider provider_readerGetPrimaryKey
+        */
+       public function testReaderGetPrimaryKey( $message, array $expected, array $row ) {
+               $reader = new BatchRowIterator( $this->mockDb(), 'some_table', array_keys( $expected ), 8675309 );
+               $this->assertEquals( $expected, $reader->extractPrimaryKeys( (object) $row ), $message );
+       }
+
+       static public function provider_readerSetFetchColumns() {
+               return array(
+
+                       array(
+                               'Must merge primary keys into select conditions',
+                               // Expected column select
+                               array( 'foo', 'bar' ),
+                               // primary keys
+                               array( 'foo' ),
+                               // setFetchColumn
+                               array( 'bar' )
+                       ),
+
+                       array(
+                               'Must not merge primary keys into the all columns selector',
+                               // Expected column select
+                               array( '*' ),
+                               // primary keys
+                               array( 'foo' ),
+                               // setFetchColumn
+                               array( '*' ),
+                       ),
+
+                       array(
+                               'Must not duplicate primary keys into column selector',
+                               // Expected column select.
+                               // TODO: figure out how to only assert the array_values portion and not the keys
+                               array( 0 => 'foo', 1 => 'bar', 3 => 'baz' ),
+                               // primary keys
+                               array( 'foo', 'bar', ),
+                               // setFetchColumn
+                               array( 'bar', 'baz' ),
+                       ),
+               );
+       }
+
+       /**
+        * @dataProvider provider_readerSetFetchColumns
+        */
+       public function testReaderSetFetchColumns( $message, array $columns, array $primaryKeys, array $fetchColumns ) {
+               $db = $this->mockDb();
+               $db->expects( $this->once() )
+                       ->method( 'select' )
+                       ->with( 'some_table', $columns ) // only testing second parameter of DatabaseBase::select
+                       ->will( $this->returnValue( new ArrayIterator( array() ) ) );
+
+               $reader = new BatchRowIterator( $db, 'some_table', $primaryKeys, 22 );
+               $reader->setFetchColumns( $fetchColumns );
+               // triggers first database select
+               $reader->rewind();
+       }
+
+       static public function provider_readerSelectConditions() {
+               return array(
+
+                       array(
+                               "With single primary key must generate id > 'value'",
+                               // Expected second iteration
+                               array( "( id_field > '3' )" ),
+                               // Primary key(s)
+                               'id_field',
+                       ),
+
+                       array(
+                               'With multiple primary keys the first conditions must use >= and the final condition must use >',
+                               // Expected second iteration
+                               array( "( id_field = '3' AND foo > '103' ) OR ( id_field > '3' )" ),
+                               // Primary key(s)
+                               array( 'id_field', 'foo' ),
+                       ),
+
+               );
+       }
+
+       /**
+        * Slightly hackish to use reflection, but asserting different parameters
+        * to consecutive calls of DatabaseBase::select in phpunit is error prone
+        *
+        * @dataProvider provider_readerSelectConditions
+        */
+       public function testReaderSelectConditionsMultiplePrimaryKeys( $message, $expectedSecondIteration, $primaryKeys, $batchSize = 3 ) {
+               $results = $this->genSelectResult( $batchSize, $batchSize * 3, function() {
+                       static $i = 0, $j = 100, $k = 1000;
+                       return array( 'id_field' => ++$i, 'foo' => ++$j, 'bar' => ++$k );
+               } );
+               $db = $this->mockDbConsecutiveSelect( $results );
+
+               $conditions = array( 'bar' => 42, 'baz' => 'hai' );
+               $reader = new BatchRowIterator( $db, 'some_table', $primaryKeys, $batchSize );
+               $reader->addConditions( $conditions );
+
+               $buildConditions = new ReflectionMethod( $reader, 'buildConditions' );
+               $buildConditions->setAccessible( true );
+
+               // On first iteration only the passed conditions must be used
+               $this->assertEquals( $conditions, $buildConditions->invoke( $reader ),
+                       'First iteration must return only the conditions passed in addConditions' );
+               $reader->rewind();
+
+               // Second iteration must use the maximum primary key of last set
+               $this->assertEquals(
+                       $conditions + $expectedSecondIteration,
+                       $buildConditions->invoke( $reader ),
+                       $message
+               );
+       }
+
+       protected function mockDbConsecutiveSelect( array $retvals ) {
+               $db = $this->mockDb();
+               $db->expects( $this->any() )
+                       ->method( 'select' )
+                       ->will( $this->consecutivelyReturnFromSelect( $retvals ) );
+               $db->expects( $this->any() )
+                       ->method( 'addQuotes' )
+                       ->will( $this->returnCallback( function( $value ) {
+                               return "'$value'"; // not real quoting: doesn't matter in test
+                       } ) );
+
+               return $db;
+       }
+
+       protected function consecutivelyReturnFromSelect( array $results ) {
+               $retvals = array();
+               foreach ( $results as $rows ) {
+                       // The DatabaseBase::select method returns iterators, so we do too.
+                       $retvals[] = $this->returnValue( new ArrayIterator( $rows ) );
+               }
+
+               return call_user_func_array( array( $this, 'onConsecutiveCalls' ), $retvals );
+       }
+
+
+       protected function genSelectResult( $batchSize, $numRows, $rowGenerator ) {
+               $res = array();
+               for ( $i = 0; $i < $numRows; $i += $batchSize ) {
+                       $rows = array();
+                       for ( $j = 0; $j < $batchSize && $i + $j < $numRows; $j++ ) {
+                               $rows [] = (object) call_user_func( $rowGenerator );
+                       }
+                       $res[] = $rows;
+               }
+               $res[] = array(); // termination condition requires empty result for last row
+               return $res;
+       }
+
+       protected function mockDb() {
+               // Cant mock from DatabaseType or DatabaseBase, they dont
+               // have the full gamut of methods
+               $databaseMysql = $this->getMockBuilder( 'DatabaseMysql' )
+                       ->disableOriginalConstructor()
+                       ->getMock();
+               $databaseMysql->expects( $this->any() )
+                       ->method( 'isOpen' )
+                       ->will( $this->returnValue( true ) );
+               return $databaseMysql;
+       }
+}