fix(backend): timeout when querying mentions

[zekexy]

What

I use a trick to avoid using primary key to solve a slow query problem. Is there any other better way?

Why

For queries like this, postgresql sometimes decides to scan the primary key instead of using the index on "visibleUserIds" field

EXPLAIN
SELECT
	"note"."id" AS "note_id"
FROM
	"note" "note"
WHERE
	'{"01GWCS86KKFQX39VH79KMD48JS"}' <@"note"."visibleUserIds"
ORDER BY
	"note"."id" DESC
LIMIT 10

However, postgresql doesn't know that sometimes users' data distribution is very uneven, which is the reason for the timeout problems some people have.

Additional info (optional)

Expected to be fast, actually very slow :

Satisfactory speed :

Checklist

• Read the contribution guide
• Test working in a local environment
• (If needed) Add story of storybook
• (If needed) Update CHANGELOG.md
• (If possible) Add tests

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.06% 🎉

Comparison is base (90b058e) 78.70% compared to head (022f99c) 78.77%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #11799      +/-   ##
===========================================
+ Coverage    78.70%   78.77%   +0.06%     
===========================================
  Files          926      924       -2     
  Lines        97860    97693     -167     
  Branches      7752     7777      +25     
===========================================
- Hits         77025    76960      -65     
+ Misses       20835    20733     -102     

Files Changed	Coverage Δ
...backend/src/server/api/endpoints/notes/mentions.ts	94.73% <100.00%> (+0.11%)	⬆️

... and 19 files with indirect coverage changes

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[syuilo]

🙏🙏🙏

[zekexy]

#7632 may be solved