What should I do if symfony propel doselect memory overflows?

Question

When symfony propel doselect, what should I do if the data taken out at one time is too large and causes memory overflow?

Answer 1

Using doSelect will take out all the rows at once and throw them into the memory. If your result set is relatively large, it will naturally explode; you can use row-by-row operation to control the memory peak:

/* 方法1.a */
$stmt = YourPeer::doSelectStmt($criteria); // <= 预处理
while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
    // 逐行操作$row
}

/* 方法1.b */
$rs = YourPeer::doSelectRS($criteria); // <= 取回一个打了包装的结果集
$rs->setFetchMode(ResultSet::FETCHMODE_ASSOC);
while($rs->next()) {
    $row = $rs->getRow();
    // 逐行操作$row
}

There are also some lazy ways that don’t cure the symptoms:

/* 方法2：如果不需要把数据结果映射成对象，可以只获取指定的字段；不映射成对象，也能省内存 */
$criteria = new Criteria();
$criteria->clearSelectColumns()->addSelectColumn(YourPeer::COL_NAME);
// 然后⋯⋯

/* 方法3：在php.ini里增大PHP运行内存限制 */
memory_limit = 1111M