如何调用Codeigniters 2 Active Record从同一查询中获取2组结果？

Question

我本质上是在为文件导出创建分块功能，并且我已经在其中建立了select-> from->。 我希望每次可以使用不同的限制/偏移值两次调用“ get”。

这是基本概念的演练。

// BallReport.php
function ProcessData(){
    //Report 1
    $query = createSelectQuery();
    $query = applyReportOneWhereValues($query);
    $results1 = CSVTool::processLargeDataSet($query, 10, 1000);

    //Report 2
    $query = createSelectQuery();
    $query = applyReportTwoWhereValues($query);
    $results2 = CSVTool::processLargeDataSet($query, 10, 1000);
}

function createSelectQuery(){
    // the select is complicated having multiple joins and sub queries 
    // so I only want to have to write this once
    $query = $this->db->select('ball.name,
            color.name,
            size.name,
            shape.name')
        ->from('ball')
        ->join('color', 'ball.color_id = color.id')
        ->join('size', 'ball.size_id = size.id')
        ->join('shape', 'ball.shape_id = shape.id');
    return $query;
}

function applyReportOneWhereValues($query){
    // I have 2 different sets of where parameters
    // But they are both using the same select
    // so I separated them into these functions
    // So I can apply the set of where statements
    // all at once
    $query = $query->where("table.color", "blue")
                   ->where("table.size" , "large")
                   ->where("table.shape", "round");
    return $query;
}

function applyReportTwoWhereValues($query){
    $query = $query->where("table.color", "red")
                   ->where("table.size" , "small")
                   ->where("table.shape", "round");
    return $query;
}

//In CSVTool.php 
public static function processLargeDataSet($query, $numberOfPages, $chunkSize){
    // Since the data set is going to be so large we want to process in chunks 
    // So that we don't hit the limit and break mid way. 
    // To do that we only call the DB in sets of 1000 rows
    for(int $i = 0; $i <= $numberOfPages: $i++){
        processRows($query, $i * $chunkSize, $chunkSize);
    }
}

function processRows($query, $offset, $limit){
    // We limit in here so each time it's called we change the offset and limit
    $query = $query->offset($offset)->limit($limit);
    $valuesToProcess = $query->get()->result_array();

    // process the rows here
}

这当然是行不通的，因为一旦processRows第一次调用$ query-> get（），所有后续调用都将引发Query error: No tables used

有什么解决办法吗？ 我没有意识到Codeigniter 2中的分块功能吗？

Answer 1

我认为您正在寻找的是“活动记录缓存”。 可以从几个不同的地方进行管理。 在这个答案中，它在ProcessData()

注意：您正在为相同的var $query分配很多东西，并且在没有充分理由的情况下将其大量传递。 而且，您经常连续多次用完全相同的值覆盖$query 。 我在您使用$query大多数地方都使用过$this->db 。

public function ProcessData()
{
    //Report 1
    $this->db->start_cache();
    //createSelectQuery(); not needed if you want all fields from one table
    applyReportOneWhereValues();
    $this->db->stop_cache();
    processLargeDataSet(10, 1000);

    //Report 2
    $this->db->flush_cache()
    $this->db->start_cache();
    //createSelectQuery(); not needed if you want all fields from one table
    applyReportTwoWhereValues();
    $this->db->stop_cache();
    processLargeDataSet(10, 1000);
    $this->db->flush_cache();
}

您的问题使用select("*")和from("table_name") ，如果您确实希望从一个表中获取所有字段，可以将其删除。 当使用get("table_name")且没有select()调用时，则假定所有字段。 IOW，查询语句为SELECT * FROM 'table_name';

根据问题的代码，您似乎不需要createSelectQuery()函数。

您的“应用在哪里”功能起作用，但使用方法链重写。

public function applyReportOneWhereValues()
{
    $this->db
      ->where("table.color", "blue")
      ->where("table.size", "large")
      ->where("table.shape", "round");
}

public function applyReportTwoWhereValues()
{
    $this->db
      ->where("table.color", "red")
      ->where("table.size", "small")
      ->where("table.shape", "round");
}

我消除了processRows()并将该逻辑合并到processLargeDataSet() 。 注意get()的用法-传递表名，限制和偏移量-消除了对select() ， from() ， limit()和offset()调用的需要。

/**
 * Process the records in chunks
 * @param int $numberOfPages The number of pages to create in the set (1 to n)
 * @param int $pageSize The number of records per page
 */
function processLargeDataSet($numberOfPages, $pageSize)
{
    if($numberOfPages < 1)
    {
        $numberOfPages = 1;
    }
    for($i = 1; $i < $numberOfPages; $i++)
    {
        $valuesToProcess = $this->db
          ->get('table', $pageSize, ($i-1) * $pageSize)
          ->result_array();
        // process the rows in $valuesToProcess
    }
}

Answer 2

这是对修订后的问题的新答案。

public function ProcessData()
{
    //Report 1
    $query_builder = $this->applyReportOneWhereValues($this->createSelectQuery());
    $this->db->stop_cache();
    $results1 = CSVTool::processLargeDataSet($query_builder, 10, 1000);
    $this->db->flush_cache();

    //Report 2
    $query_builder = $this->applyReportTwoWhereValues($this->createSelectQuery());
    $this->db->stop_cache();
    $results2 = CSVTool::processLargeDataSet($query_builder, 10, 1000);
    $this->db->flush_cache(); //just to be safe
}

public function createSelectQuery()
{
    $this->db->start_cache();
    return $this->db->select('ball.name, color.name, size.name, shape.name')
        ->join('color', 'ball.color_id = color.id')
        ->join('size', 'ball.size_id = size.id')
        ->join('shape', 'ball.shape_id = shape.id');
}

public function applyReportOneWhereValues($query_builder)
{
    return $query_builder
      ->where("table.color", "blue")
      ->where("table.size", "large")
      ->where("table.shape", "round");
}

public function applyReportTwoWhereValues($query_builder)
{
    return $query_builder
      ->where("table.color", "red")
      ->where("table.size", "small")
      ->where("table.shape", "round");
}

在CSVTool.php中

/**
 * Process the records in chunks
 * @param CI_DB_query_builder $qb An instance of the CI_DB_query_builder class
 * @param int $numberOfPages The number of pages to create in the set (1 to n)
 * @param int $pageSize The number of records per page
 */
public static function processLargeDataSet($qb, $numberOfPages, $pageSize)
{
    if($numberOfPages < 1)
    {
        $numberOfPages = 1;
    }
    for($i = 1; $i < $numberOfPages; $i++)
    {
        $valuesToProcess = $qb
          ->get('ball', $pageSize, $i - 1 * $pageSize)
          ->result_array();
        // process the rows in $valuesToProcess
    }
}