哪个MEAN生成器 - javascript(Which MEAN Generator - javascript)

 我相信最耗时的部分应该是执行查询。 如果你使用whereIn ，那么我认为你只能执行一次查询，然后遍历结果。 我没有测试过，但它应该是这样的： 
 
$purchasesByYear = \App\Inventory::select('purchase_year',
    DB::raw('count(*) as purchase_count'))
        ->whereIn('purchase_year', $purchaseYears)
        ->groupBy('purchase_year')->get();
 
 我认为减少查询执行次数将是阻止其慢慢运行的主要机会。 此外，我认为如果您还没有这样做，那么在purchase_year中添加索引应该会有所帮助。 
 
 你可以使用一些数学来代替很多其他条件来处理这些年份的分组。 这实际上可能稍慢，但代码重复性稍差，我相信你对这部分所做的任何事情都将是微观优化，而不是你可以对查询部分做什么。 我的建议： 
 
foreach ($purchasesByYear as $purchaseYear) {
    $year = $purchaseYear->purchase_year;
    if ($year < 1960) {
        $yearRange = 'Pre 1960';
    } else {
        // subtract one until the year is a multiple of five
        while ($year % 5) { $year--; }
        // then construct the range string using the starting number
        $yearRange = $year.'-'.($year+4);
    }
    if (isset($chartData[$yearRange])) {
        $chartData[$yearRange] += $purchaseYear->purchase_count;
    } else {
        $chartData[$yearRange] = $purchaseYear->purchase_count;
    }
}

I believe the most time consuming part should be executing the query. If you use whereIn, then I think you can execute the query only once, and then loop over the results. I haven't tested it, but it should be something like this:
 
$purchasesByYear = \App\Inventory::select('purchase_year',
    DB::raw('count(*) as purchase_count'))
        ->whereIn('purchase_year', $purchaseYears)
        ->groupBy('purchase_year')->get();
 
I think reducing the number of query executions will be the main opportunity to keep this from running slowly. Also, I think adding an index to purchase_year should be helpful if you have not already done so.
 
Instead of a lot of elseif conditions to handle grouping the years, you could use some math. This might actually be slightly slower, but the code would be a little less repetitive, and I believe anything you do to this part will be a micro-optimization compared to what you can do with the query part. My suggestion:
 
foreach ($purchasesByYear as $purchaseYear) {
    $year = $purchaseYear->purchase_year;
    if ($year < 1960) {
        $yearRange = 'Pre 1960';
    } else {
        // subtract one until the year is a multiple of five
        while ($year % 5) { $year--; }
        // then construct the range string using the starting number
        $yearRange = $year.'-'.($year+4);
    }
    if (isset($chartData[$yearRange])) {
        $chartData[$yearRange] += $purchaseYear->purchase_count;
    } else {
        $chartData[$yearRange] = $purchaseYear->purchase_count;
    }
}