Symfony应用程序-如何将计算字段添加到Propel对象? [英] Symfony app - how to add calculated fields to Propel objects?
问题描述
处理Propel对象的计算字段的最佳方法是什么?
What is the best way of working with calculated fields of Propel objects?
说我有一个对象"Customer"，它有一个对应的表"customers"，并且每一列都对应于我对象的一个属性.我想做的是:在视图A而不是视图B和C上使用该属性时，将计算出的属性已完成订单数"添加到我的对象中.
Say I have an object "Customer" that has a corresponding table "customers" and each column corresponds to an attribute of my object. What I would like to do is: add a calculated attribute "Number of completed orders" to my object when using it on View A but not on Views B and C.
计算出的属性是通过ID链接到我的客户"对象的订单"对象的COUNT().
The calculated attribute is a COUNT() of "Order" objects linked to my "Customer" object via ID.
我现在要做的是首先选择所有Customer对象，然后为所有对象迭代计算Orders，但是我认为在单个查询中进行操作将提高性能.但是我无法正确地水化"我的Propel对象，因为它不包含计算字段的定义.
What I can do now is to first select all Customer objects, then iteratively count Orders for all of them, but I'd think doing it in a single query would improve performance. But I cannot properly "hydrate" my Propel object since it does not contain the definition of the calculated field(s).
您将如何处理?
推荐答案
有几种选择.首先，是在数据库中创建一个视图，该视图将为您完成计数，类似于我在此处的答案.我是针对当前的Symfony项目执行此操作的，在该项目中，给定表的只读属性实际上比表本身宽得多.这是我的建议，因为分组列(max()，count()等)始终是只读的.
There are several choices. First, is to create a view in your DB that will do the counts for you, similar to my answer here. I do this for a current Symfony project I work on where the read-only attributes for a given table are actually much, much wider than the table itself. This is my recommendation since grouping columns (max(), count(), etc) are read-only anyway.
其他选项实际上是将此功能构建到模型中.您绝对可以自己进行保湿，但是有点复杂.这是粗糙的步骤
The other options are to actually build this functionality into your model. You absolutely CAN do this hydration yourself, but it's a bit complicated. Here's the rough steps
- 将列作为受保护的数据成员添加到您的 Table 类中.
- 为这些列写适当的吸气剂和吸气剂
- 覆盖水合物方法，并在其中用来自其他查询的数据填充新列.确保将parent :: hydrate()作为第一行
- Add the columns to your Table class as protected data members.
- Write the appropriate getters and setters for these columns
- Override the hydrate method and within, populate your new columns with the data from other queries. Make sure to call parent::hydrate() as the first line
但是，这并没有比您正在谈论的要好得多.您仍然需要 N + 1个查询来检索单个记录集.但是，您可以在第3步中发挥创意，使 N 是计算的列数，而不是返回的行数.
However, this isn't much better than what you're talking about already. You'll still need N + 1 queries to retrieve a single record set. However, you can get creative in step #3 so that N is the number of calculated columns, not the number of rows returned.
另一种选择是在 Table Peer类上创建自定义选择方法.
Another option is to create a custom selection method on your TablePeer class.
- 从上方执行步骤1和2.
- 编写您将通过Propel :: getConnection()流程手动查询的自定义SQL.
- 通过遍历结果集手动创建数据集，并在此时处理自定义水合，以确保在doSelect流程使用时不会破坏水合.
这是这种方法的一个例子
Here's an example of this approach
<?php
class TablePeer extends BaseTablePeer
{
public static function selectWithCalculatedColumns()
{
// Do our custom selection, still using propel's column data constants
$sql = "
SELECT " . implode( ', ', self::getFieldNames( BasePeer::TYPE_COLNAME ) ) . "
, count(" . JoinedTablePeer::ID . ") AS calc_col
FROM " . self::TABLE_NAME . "
LEFT JOIN " . JoinedTablePeer::TABLE_NAME . "
ON " . JoinedTablePeer::ID . " = " . self::FKEY_COLUMN
;
// Get the result set
$conn = Propel::getConnection();
$stmt = $conn->prepareStatement( $sql );
$rs = $stmt->executeQuery( array(), ResultSet::FETCHMODE_NUM );
// Create an empty rowset
$rowset = array();
// Iterate over the result set
while ( $rs->next() )
{
// Create each row individually
$row = new Table();
$startcol = $row->hydrate( $rs );
// Use our custom setter to populate the new column
$row->setCalcCol( $row->get( $startcol ) );
$rowset[] = $row;
}
return $rowset;
}
}
对于您的问题，可能还有其他解决方案，但是这些解决方案是我所不了解的.祝你好运！
There may be other solutions to your problem, but they are beyond my knowledge. Best of luck!
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