SQLite: Replace LIKE with SUBSTR for file path matching

[uklotzde]

This refactoring makes SqlLikeWildcardEscaper obsolete and ensures that file paths in the database are matched case-sensitive.

Follow-up of #4146. It also fixes the incorrect file path matching in TrackDAO. No backport to 2.3.

Note: We don't properly escape SQL LIKE wildcards in other, informal search queries, e.g. for crates. But this is just a minor issue and if SqlLikeWildcardEscaper is ever needed again it could be brought back. Currently it is unused and should disappear.

[coveralls]

Pull Request Test Coverage Report for Build 1105672637

• 3 of 12 (25.0%) changed or added relevant lines in 2 files are covered.
• 992 unchanged lines in 12 files lost coverage.
• Overall coverage decreased (-0.04%) to 25.989%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/library/dao/trackdao.cpp	1	10	10.0%

Files with Coverage Reduction	New Missed Lines	%
src/track/serato/beatgrid.cpp	2	62.5%
src/engine/enginebuffer.cpp	14	86.26%
src/track/beatutils.cpp	17	48.44%
src/util/db/dbconnection.cpp	18	69.78%
src/controllers/scripting/controllerscriptenginebase.cpp	31	39.42%
src/util/cmdlineargs.cpp	43	72.73%
src/library/basetracktablemodel.cpp	64	21.99%
src/library/dlgtrackinfo.cpp	84	0%
src/engine/controls/bpmcontrol.cpp	95	63.44%
src/coreservices.cpp	115	0%

Totals
Change from base Build 1083902170:	-0.04%
Covered Lines:	19997
Relevant Lines:	76944

---

💛 - Coveralls

[Be-ing]

Are you sure this does not affect 2.3?

[uklotzde]

Are you sure this does not affect 2.3?

As I mentioned somehow it does, but no one complained so far. I won't fix it, let's move forward.

[uklotzde]

I don't want to apply this to 2.3, too risky. We are even installing a custom sqliteLike() function for handling UTF-16. Not sure how SUBSTR behaves compared to LIKE or if it matters. Edit: The sqliteLike() might still be needed for i18n-aware filtering, not sure. Strings are in fact stored as UTF-8 by SQLite.

We cannot fix all the issues for each and every version. Hopefully we can get rid of the legacy database code and Qt UTF-16 strings someday.

[uklotzde]

The database code is completely broken because the LIKE operator is tweaked unconditionally for searching, i.e. by treating 'ä' like 'a'. But we also used it for exact file path prefix matches which obviously doesn't work as intended and could cause false positives.

[uklotzde]

The modified test even succeeds for 2.3.

[Holzhaus]

We usually don't explain the obvious in comments, but in this case it might be good to add a comment that 1 refers to the first character in the string (i.e. it's not 0-based like arrays/lists/whatever in C/C++ are).

[Holzhaus]

Another way to implement something like STARTSWITH() would be

INSTR(track_locations.location, :oldDirectoryPrefix) = 1

but I guess that would be less performant.

[uklotzde]

I won't replicate the same comment at 3 different locations. This can be looked up in the SQLite docs.

Using INSTR is less chatty, we should probably use that!

[uklotzde]

The naming of the variables clearly reveals the purpose, so there is no need to explain the 1-based indexing.

Thinking about the performance implications SUBSTR might in fact be faster than INSTR, because you have to know the outer context for optimizing the INSTR operation. I will keep using it in the aoide backend.

[Holzhaus]

LGTM, thank you!