bugfix: Columns alias expanding

[systay]

Description

We were not rewriting column aliases correctly. The rules that MySQL 8.0.x follows are not well documented, and in some cases we have found that the manual is not agreeing with our experiments.

This PR changes the alias rewriting rules to make sure to rewrite aliases early in the planning process, and removes the complex column lookup logic, which is no longer needed.

Related Issue(s)

Fixes #14869

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

[vitess-bot]

Review Checklist

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General

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• vtctl command output order should be stable and awk-able.

[codecov]

Codecov Report

Attention: 93 lines in your changes are missing coverage. Please review.

Comparison is base (eddb39e) 47.29% compared to head (1a1ec81) 47.25%.
Report is 4 commits behind head on main.

Files	Patch %	Lines
go/vt/vtgate/semantics/early_rewriter.go	85.90%	22 Missing and 10 partials ⚠️
...tgate/planbuilder/operators/aggregation_pushing.go	0.00%	25 Missing ⚠️
...vt/vtgate/planbuilder/operators/queryprojection.go	0.00%	20 Missing ⚠️
go/vt/vtgate/planbuilder/operators/aggregator.go	0.00%	8 Missing ⚠️
.../vtgate/planbuilder/operators/horizon_expanding.go	0.00%	2 Missing ⚠️
go/vt/vtgate/planbuilder/operators/phases.go	0.00%	2 Missing ⚠️
.../vt/vtgate/planbuilder/operators/query_planning.go	0.00%	2 Missing ⚠️
go/vt/vtgate/planbuilder/operators/SQL_builder.go	0.00%	1 Missing ⚠️
go/vt/vtgate/planbuilder/operators/distinct.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #14935      +/-   ##
==========================================
- Coverage   47.29%   47.25%   -0.05%     
==========================================
  Files        1137     1137              
  Lines      238684   238681       -3     
==========================================
- Hits       112895   112781     -114     
- Misses     117168   117304     +136     
+ Partials     8621     8596      -25     

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[systay]

The codecov report doesn't seem to take into account the unit tests we have in the planbuilder package, that also cover the planbuilder/operators package 🤷

[harshit-gangal]

what is the expectation where order by and group by has alias referencing to a subquery

[systay]

found a wrong plan output

me and @harshit-gangal looked at this, and it's a real issue, but unrelated to these changes. I'll work on fixing this separately: #14950

does not need to block this PR

[frouioui]

The codecov report doesn't seem to take into account the unit tests we have in the planbuilder package, that also cover the planbuilder/operators package 🤷

We should look into that @mattlord. I can see the base branch reports 0.00% of coverage for these paths.