Planner Bug: Joins inside derived table

[systay]

Description

In some situations, the vtgate planner was producing really bad plans around derived tables and columns.

In this PR I reworked a lot of the logic around derived tables and their columns.

Related Issue(s)

Fixes #14993

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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[codecov]

Codecov Report

Attention: 136 lines in your changes are missing coverage. Please review.

Comparison is base (eddb39e) 47.29% compared to head (57aed9b) 70.60%.
Report is 114 commits behind head on main.

Files	Patch %	Lines
go/vt/mysqlctl/builtinbackupengine.go	12.90%	54 Missing ⚠️
go/vt/mysqlctl/backupengine.go	0.00%	20 Missing ⚠️
go/vt/mysqlctl/xtrabackupengine.go	0.00%	15 Missing ⚠️
go/vt/schemadiff/column.go	70.83%	7 Missing ⚠️
go/mysql/conn.go	53.84%	6 Missing ⚠️
go/vt/mysqlctl/backup.go	37.50%	5 Missing ⚠️
go/mysql/capabilities/capability.go	91.48%	4 Missing ⚠️
go/mysql/query.go	77.77%	4 Missing ⚠️
go/vt/mysqlctl/schema.go	72.72%	3 Missing ⚠️
go/vt/schemadiff/schema.go	92.10%	3 Missing ⚠️
... and 10 more

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #14974       +/-   ##
===========================================
+ Coverage   47.29%   70.60%   +23.30%     
===========================================
  Files        1137     1379      +242     
  Lines      238684   183009    -55675     
===========================================
+ Hits       112895   129209    +16314     
+ Misses     117168    53800    -63368     
+ Partials     8621        0     -8621     

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[frouioui]

we do not have a proper clone function for DerivedTable?

[systay]

nope. I'll add one

[systay]

hmm... I changed my mind. Don't think we need one. This is the only place we try to clone it, and it's not a pure cloning anyway

[frouioui]

Besides that failing plan test and the comment I left, it looks good to me! That's a really good enhancement / bug fix, thank you 🙏🏻

Codecov is spanning a bunch of warnings in a lot of places in this PR, is this because of the cross-package coverage missing or is it due to actual missing plan tests?

[systay]

This last test will fail without the changes in this PR:

Error: Received unexpected error:
target: ks_union.-80.primary: vttablet: rpc error: code = NotFound desc = Unknown column 't2.id4' in 'field list' (errno 1054) (sqlstate 42S22) (CallerID: userData1): Sql: "select distinct t2.id4, 1, dt.`t2.id4` from (select t2.id4 as `t2.id4` from t2) as dt", BindVars: {}
target: ks_union.80-.primary: vttablet: rpc error: code = NotFound desc = Unknown column 't2.id4' in 'field list' (errno 1054) (sqlstate 42S22) (CallerID: userData1): Sql: "select distinct t2.id4, 1, dt.`t2.id4` from (select t2.id4 as `t2.id4` from t2) as dt", BindVars: {} (errno 1054) (sqlstate 42S22) during query: SELECT COUNT(*) FROM (SELECT DISTINCT t1.id1 FROM t1 JOIN t2 ON t1.id1 = t2.id4) dt