feat: optimize user mount cache

[Altahrim]

Optimize requests like:

SELECT
  `storage_id`,
  `root_id`,
  `user_id`,
  `mount_point`,
  `mount_id`,
  `f`.`path`,
  `mount_provider_class`
FROM
  `oc_mounts` `m`
  INNER JOIN `oc_filecache` `f` ON `m`.`root_id` = `f`.`fileid`
WHERE
  (`storage_id` = ?)
  AND (
    (`f`.`fileid` = ?)
    OR (`f`.`path` = ?)
    OR (
      `CONCAT` (`f`.`path`, ?) = SUBSTRING (?, ..., `CHAR_LENGTH` (`f`.`path`) + ?)
    )
  )

TODO

• Is it better to add both fields so DB can choose the best path? ⇒ Changed

Explain

Before

+------+-------------+-------+--------+-----------------------------------------------------------+--------------------+---------+--------------+-------+-------------+
| id   | select_type | table | type   | possible_keys                                             | key                | key_len | ref          | rows  | Extra       |
+------+-------------+-------+--------+-----------------------------------------------------------+--------------------+---------+--------------+-------+-------------+
|    1 | SIMPLE      | m     | ref    | mounts_storage_index,mounts_root_index,mount_user_storage | mount_user_storage | 8       | const        | 64048 |             |
|    1 | SIMPLE      | f     | eq_ref | PRIMARY                                                   | PRIMARY            | 8       | oc.m.root_id | 1     | Using where |
+------+-------------+-------+--------+-----------------------------------------------------------+--------------------+---------+--------------+-------+-------------+

After

+------+-------------+-------+------+-------------------------------------------------------------------------------------------------------------+---------------------+---------+-------------+-------+-------------+
| id   | select_type | table | type | possible_keys                                                                                               | key                 | key_len | ref         | rows  | Extra       |
+------+-------------+-------+------+-------------------------------------------------------------------------------------------------------------+---------------------+---------+-------------+-------+-------------+
|    1 | SIMPLE      | f     | ref  | PRIMARY,fs_storage_path_hash,fs_storage_mimetype,fs_storage_mimepart,fs_storage_size,fs_storage_path_prefix | fs_storage_mimetype | 8       | const       | 20918 | Using where |
|    1 | SIMPLE      | m     | ref  | mounts_root_index                                                                                           | mounts_root_index   | 8       | oc.f.fileid | 7     |             |
+------+-------------+-------+------+-------------------------------------------------------------------------------------------------------------+---------------------+---------+-------------+-------+-------------+

The change allows to filter on filecache first

(Rough) Benchmark

• Before: ≈ 400 ms
• After : ≈ 70 ms

[icewind1991]

I would expect the performance comparison to go the other way around for instances that have a few mounts per user but a lot of files. Adding both comparisons and hoping the DB knows what to do is probably for the best.

[Altahrim]

On my instance, having both still filter on oc_mounts first and is slower…

[Altahrim]

I was able to trigger the same EXPLAIN by adding a condition to the join: AND m.storage_id = f.storage
Then, I hope the DB will choose wisely :)

[Altahrim]

/backport to stable33