In code search, get code unit accessible repos in one (main) query

[hoitih]

Fix for #12849.

The slow search that non-Admin users experienced was in my opinion not caused by the fact that some queries were slow, but a lot of querying was done each time the 'explore/code' page was rendered or the 'search' was actually performed.
So in file routers/explore/web/code.go I added a check if a keyword to search for was present, otherwise the logic for searching is skipped. That fixed slow rendering of an empty page 'explore/code'.
When actually performing a search, first a list is created with Repository ID's where the user has access to (when the user is not an Admin or Guest user). That took quite a lot of time: first a list was retrieved using a db-query in method FindUserAccessibleRepoIDs() to which a user has general access, followed by logic to check for each repository if the user has access at Code level. This check for each repository leads to a lot of queries in case of a lot of repositories.

Since method FindUserAccessibleRepoIDs() was only used on the explore/code page, I changed it's name to FindUserCodeAccessibleRepoIDs() logic to return only repository ID's the user has access to at Code level and deleted the code in file routers/explore/web/code.go that checked this.

To make FindUserCodeAccessibleRepoIDs() only return repository ID's the user has access to at Code level, I changed generic method accessibleRepositoryCondition(user) to accept a second argument unit.Type. In this method I made sure it worked in the same way as before if an unit.TypeInvalid was passed as argument. In all other places this method was used I specified this unit.TypeInvalid. Only within method FindUserCodeAccessibleRepoIDs() I passed unit.TypeCode as second argument to accessibleRepositoryCondition(). Since only 'general' access to a repository is registered in db-table access, a query to this table cannot be used if looking for access given at the level of a specific unit.Type. That kind of access is registered in db-table team_unit. I added 'joins' for that in de db WHERE-condition. Since the level of Access to a unit.Type can be 'None' I added a check for this too, to making sure it is at least 'Read'. Furthermore I added a condition for adding repository ID's where the user is (external) collaborator in.

Tested for Admin and non-Admin users with Elastic as Code Indexer.
In development mode with SQLite on Windows10/WSL2 with go 1.17.7.

In bindata mode in a docker container (build with the provided Dockerfile) and with PostgreSQL as database.

[zeripath]

Heya!

Thanks for the PR.

I think it would be helpful if you updated your PR description to describe your changes and the reasoning behind them. I'm not saying you've done it wrong here - just that we need to get better at describing how your PR actually works and improves things.

This section of code is complex and difficult to review.

[hoitih]

Hello there!

Update the PR description.

[codecov-commenter]

Codecov Report

Merging #19764 (9be48b3) into main (ad551bf) will decrease coverage by 0.08%.
The diff coverage is 25.84%.

@@            Coverage Diff             @@
##             main   #19764      +/-   ##
==========================================
- Coverage   47.40%   47.31%   -0.09%     
==========================================
  Files         958      957       -1     
  Lines      133604   133334     -270     
==========================================
- Hits        63331    63084     -247     
+ Misses      62612    62583      -29     
- Partials     7661     7667       +6     

Impacted Files	Coverage Δ
routers/web/explore/code.go	0.00% <0.00%> (ø)
models/lfs.go	21.93% <50.00%> (ø)
models/repo_list.go	80.25% <60.60%> (-2.15%)	⬇️
models/issue.go	54.18% <100.00%> (-0.25%)	⬇️
models/org.go	62.99% <100.00%> (ø)
models/repo/user_repo.go	0.00% <0.00%> (-26.67%)	⬇️
models/db/context.go	70.10% <0.00%> (-14.90%)	⬇️
modules/queue/queue_channel.go	76.85% <0.00%> (-4.63%)	⬇️
models/organization/org_user.go	92.53% <0.00%> (-4.61%)	⬇️
models/repo/repo_indexer.go	47.69% <0.00%> (-3.74%)	⬇️
... and 85 more

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[zeripath]

I wonder if it would be helpful to add an alias for unit.TypeInvalid unit.TypeAny that we could use instead for these search conditions.

(I'm not sure about this though but it would look a bit better..)

[zeripath]

I was meaning that you should put the description of what the PR is doing from (#19764 (comment)) into the opening comment of the PR.

[lunny]

Please resolve the conflicts.

[hoitih]

Please resolve the conflicts.

Done