BatchRowIterator.php

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<?php
 
use Wikimedia\Rdbms\IReadableDatabase;
 
class BatchRowIterator implements RecursiveIterator {
 
    protected $db;
 
    protected $table;
 
    protected $primaryKey;
 
    protected $batchSize;
 
    protected $conditions = [];
 
    protected $joinConditions = [];
 
    protected $fetchColumns;
 
    protected $orderBy;
 
    private $current = [];
 
    private $key = -1;
 
    protected $options = [];
 
    protected $caller;
 
    public function __construct( IReadableDatabase $db, $table, $primaryKey, $batchSize ) {
        if ( $batchSize < 1 ) {
            throw new InvalidArgumentException( '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;
    }
 
    public function addConditions( array $conditions ) {
        $this->conditions = array_merge( $this->conditions, $conditions );
    }
 
    public function addOptions( array $options ) {
        $this->options = array_merge( $this->options, $options );
    }
 
    public function addJoinConditions( array $conditions ) {
        $this->joinConditions = array_merge( $this->joinConditions, $conditions );
    }
 
    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
            ) );
        }
    }
 
    public function setCaller( $caller ) {
        $this->caller = $caller;
 
        return $this;
    }
 
    public function extractPrimaryKeys( $row ) {
        $pk = [];
        foreach ( $this->primaryKey as $alias => $column ) {
            $name = is_numeric( $alias ) ? $column : $alias;
            $pk[$name] = $row->{$name};
        }
        return $pk;
    }
 
    public function current(): array {
        return $this->current;
    }
 
    public function key(): int {
        return $this->key;
    }
 
    public function rewind(): void {
        $this->key = -1; // self::next() will turn this into 0
        $this->current = [];
        $this->next();
    }
 
    public function valid(): bool {
        return (bool)$this->current;
    }
 
    public function hasChildren(): bool {
        return $this->current && count( $this->current );
    }
 
    public function getChildren(): ?RecursiveIterator {
        return new NotRecursiveIterator( new ArrayIterator( $this->current ) );
    }
 
    public function next(): void {
        $caller = __METHOD__;
        if ( (string)$this->caller !== '' ) {
            $caller .= " (for {$this->caller})";
        }
 
        $res = $this->db->select(
            $this->table,
            $this->fetchColumns,
            $this->buildConditions(),
            $caller,
            [
                'LIMIT' => $this->batchSize,
                'ORDER BY' => $this->orderBy,
            ] + $this->options,
            $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++;
    }
 
    protected function buildConditions() {
        if ( !$this->current ) {
            return $this->conditions;
        }
 
        $maxRow = end( $this->current );
        $maximumValues = [];
        foreach ( $this->primaryKey as $alias => $column ) {
            $name = is_numeric( $alias ) ? $column : $alias;
            $maximumValues[$column] = $maxRow->$name;
        }
 
        $conditions = $this->conditions;
        $conditions[] = $this->db->buildComparison( '>', $maximumValues );
 
        return $conditions;
    }
}