Performance enhancement snippet (pre PR discussion)

[cjke]

The following is a working (but with possible regressions) snippet to reduce the query load of fetching many acf fields.

Summary

The overarching principal is:

1. pass in an array of key/value pairs (the field is key, as the type is not likely to be unique)
2. a new method ("fields" or "bulk" or whatever) makes a generic select * from wp_postmetawherepost_id in ('106') via $this->post->meta
3. we filter down the meta values to just the keys we passed in
4. feed those meta models back into the field factory.

This, from elementary testing, changes the query to 1 + N (1 for post + N per acf field) to 2 (1 for post + 1 for all meta).

Before:

After:

Code changes

    // Sample usage
    Staff::find(1);
    $fields = $staff->acf->fields([
        'staff_short_description' => 'wysiwyg',
        'staff_description' => 'wysiwyg',
        'staff_role' => 'text',
    ]);

    dd($fields); // (see screenshot)

The following ACF fields would need to be modified:

    // AdvancedCustomFields.php
    // Add new bulk/fields/etc method
    public function fields($fields)
    {
        // whereIn limits the fields down to just the keys we are looking for
        // feed the same stuff into the Factory
        return $this->post
            ->meta
            ->whereIn('meta_key', array_keys($fields))
            ->mapWithKeys(function($field) use ($fields)
            {
                $value = FieldFactory::make($field, $this->post, snake_case($fields[$field->meta_key]))->get();
                return [$field->meta_key => $value];
            });
    }

And BasicField (at minimum):

    // BasicField
    // This bit is the tricky bit - we need to remove the query from fetchValue 
    // possibly into a seperate method (maybe performQuery)
    public function fetchValue($field)
    {
    // $postMeta = $this->postMeta->where(
    //    $this->getKeyName(), $this->post->getKey()
    // )->where('meta_key', $field)->first();

    if (isset($postMeta->meta_value) and ! is_null($postMeta->meta_value)) {
        $value = $postMeta->meta_value;
        ...
        // remaining code is the same

Concerns

My major concern is I am missing something major - as to why the per field query is needed (the removed lines in BasicField).

Obviously regression is reasonably big too.

Thoughts before kicking off a PR? I'm extremely short on time (who isn't?) at the moment - so need to be careful how I allocate resources.