Lookup join without boxing

[richardstartin]

We still see a large number of boxed integers when joining on an INT column, this replaces PrimaryKey with JoinKey which has a specialised implementation when all the keys are fixed width.

[codecov-commenter]

Codecov Report

Merging #8208 (a2614bc) into master (916d807) will decrease coverage by 6.67%.
The diff coverage is 64.22%.

@@             Coverage Diff              @@
##             master    #8208      +/-   ##
============================================
- Coverage     71.02%   64.35%   -6.68%     
- Complexity     4314     4315       +1     
============================================
  Files          1626     1584      -42     
  Lines         84929    83153    -1776     
  Branches      12783    12596     -187     
============================================
- Hits          60325    53517    -6808     
- Misses        20462    25786    +5324     
+ Partials       4142     3850     -292     

Flag	Coverage Δ
integration1	?
integration2	?
unittests1	67.37% <64.22%> (-0.02%)	⬇️
unittests2	14.12% <0.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...pache/pinot/core/data/manager/offline/JoinKey.java	20.00% <20.00%> (ø)
...ore/data/manager/offline/VariableWidthJoinKey.java	58.33% <58.33%> (ø)
...t/core/data/manager/offline/FixedWidthJoinKey.java	71.42% <71.42%> (ø)
...or/transform/function/LookupTransformFunction.java	74.64% <72.97%> (-4.41%)	⬇️
...ata/manager/offline/DimensionTableDataManager.java	83.58% <78.94%> (-2.70%)	⬇️
...a/org/apache/pinot/common/metrics/MinionMeter.java	0.00% <0.00%> (-100.00%)	⬇️
...g/apache/pinot/common/metrics/ControllerMeter.java	0.00% <0.00%> (-100.00%)	⬇️
.../apache/pinot/common/metrics/BrokerQueryPhase.java	0.00% <0.00%> (-100.00%)	⬇️
.../apache/pinot/common/metrics/MinionQueryPhase.java	0.00% <0.00%> (-100.00%)	⬇️
...ache/pinot/server/access/AccessControlFactory.java	0.00% <0.00%> (-100.00%)	⬇️
... and 380 more

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[richardstartin]

I can't establish whether this actually improves performance or not, though it definitely reduces allocation rate. I'm closing this in favour of delaying joins until after group by evaluation. It can be reopened later if necessary.