[stable23] Use explicit cast to make use of index

[juliusknorr]

This ensures that indexes of oc_share are being used on MySQL when fetching the shares of a user during mountpoint setup, where otherwise a full table scan would happen.

@nickvergessen I'm wondering if there is a specific reason that the MySQLExpressionBuilder does not implement any actual casting when using castColumn(). Is that something that we should rather do in the server then maybe?

EXPLAIN before

+------+-------------+-------+--------+----------------------------------------+----------------------------+---------+-------------------------+------+-------------------------------------------------+
| id   | select_type | table | type   | possible_keys                          | key                        | key_len | ref                     | rows | Extra                                           |
+------+-------------+-------+--------+----------------------------------------+----------------------------+---------+-------------------------+------+-------------------------------------------------+
|    1 | SIMPLE      | db    | const  | PRIMARY                                | PRIMARY                    | 4       | const                   | 1    | Using index; Using temporary; Using filesort    |
|    1 | SIMPLE      | ds    | ref    | PRIMARY,deck_stacks_board_id_index     | deck_stacks_board_id_index | 8       | const                   | 1    | Using index                                     |
|    1 | SIMPLE      | dc    | ref    | PRIMARY,deck_cards_stack_id_index      | deck_cards_stack_id_index  | 8       | nextcloud.ds.id         | 1    | Using where; Using index                        |
|    1 | SIMPLE      | s     | ALL    | item_share_type_index,share_with_index | NULL                       | NULL    | NULL                    | 1290 | Using where; Using join buffer (flat, BNL join) |
|    1 | SIMPLE      | f     | eq_ref | PRIMARY,fs_id_storage_size             | PRIMARY                    | 8       | nextcloud.s.file_source | 1    | Using where                                     |
|    1 | SIMPLE      | st    | eq_ref | PRIMARY                                | PRIMARY                    | 8       | nextcloud.f.storage     | 1    | Using where                                     |
+------+-------------+-------+--------+----------------------------------------+----------------------------+---------+-------------------------+------+-------------------------------------------------+

EXPLAIN after

+------+-------------+-------+--------+----------------------------------------+----------------------------+---------+-------------------------+------+----------------------------------------------+
| id   | select_type | table | type   | possible_keys                          | key                        | key_len | ref                     | rows | Extra                                        |
+------+-------------+-------+--------+----------------------------------------+----------------------------+---------+-------------------------+------+----------------------------------------------+
|    1 | SIMPLE      | db    | const  | PRIMARY                                | PRIMARY                    | 4       | const                   | 1    | Using index; Using temporary; Using filesort |
|    1 | SIMPLE      | ds    | ref    | PRIMARY,deck_stacks_board_id_index     | deck_stacks_board_id_index | 8       | const                   | 1    | Using index                                  |
|    1 | SIMPLE      | dc    | ref    | deck_cards_stack_id_index              | deck_cards_stack_id_index  | 8       | nextcloud.ds.id         | 1    | Using where; Using index                     |
|    1 | SIMPLE      | s     | ref    | item_share_type_index,share_with_index | share_with_index           | 1023    | func                    | 36   | Using index condition; Using where           |
|    1 | SIMPLE      | f     | eq_ref | PRIMARY,fs_id_storage_size             | PRIMARY                    | 8       | nextcloud.s.file_source | 1    | Using where                                  |
|    1 | SIMPLE      | st    | eq_ref | PRIMARY                                | PRIMARY                    | 8       | nextcloud.f.storage     | 1    | Using where                                  |
+------+-------------+-------+--------+----------------------------------------+----------------------------+---------+-------------------------+------+----------------------------------------------+

[nickvergessen]

I'm wondering if there is a specific reason that the MySQLExpressionBuilder does not implement any actual casting when using castColumn(). Is that something that we should rather do in the server then maybe?

Looks like it makes sense. It was not added so far as currently it was only needed for oracle and postgres when dealing with TEXT and having to convert that to CHAR for comparisons.

[juliusknorr]

Changed the base to 23 since on 24 we have this fixed in the server.

[juliusknorr]

/backport to stable22

[juliusknorr]

/backport to stable21

[luka-nextcloud]

The snippet is used twice in the code. I think it would be a good idea to create a temp function for that as that function will be removed in the coming version of nextcloud.

[juliusknorr]

For newer server releases this will be taken care of in the query builder abstraction with nextcloud/server#30471, so I'd say we stick to those now for the bugfix only releases.