fix: Optimize not to call getNullCount as much as possible

[kazuyukitanimura]

Which issue does this PR close?

Rationale for this change

This PR reduces to call getNullCount as much as possible

What changes are included in this PR?

Calling getNullCount is expensive so reusing the number rather than re-calculating

How are these changes tested?

Existing test

[kazuyukitanimura]

Before

After

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 5.22388% with 127 lines in your changes missing coverage. Please review.

Project coverage is 54.02%. Comparing base (4fe43ad) to head (a773832). Report is 9 commits behind head on main.

Files	Patch %	Lines
...in/java/org/apache/arrow/c/CometArrayExporter.java	0.00%	54 Missing :warning:
...n/java/org/apache/comet/vector/CometMapVector.java	0.00%	16 Missing :warning:
...main/java/org/apache/comet/vector/CometVector.java	0.00%	13 Missing :warning:
...ava/org/apache/comet/vector/CometStructVector.java	0.00%	9 Missing :warning:
...ain/scala/org/apache/comet/vector/NativeUtil.scala	0.00%	8 Missing :warning:
.../java/org/apache/comet/vector/CometLazyVector.java	0.00%	6 Missing :warning:
...in/java/org/apache/comet/parquet/ColumnReader.java	0.00%	4 Missing :warning:
.../src/main/java/org/apache/comet/parquet/Utils.java	20.00%	4 Missing :warning:
...org/apache/comet/vector/CometDictionaryVector.java	0.00%	4 Missing :warning:
.../java/org/apache/comet/vector/CometListVector.java	0.00%	3 Missing :warning:
... and 4 more

Additional details and impacted files

@@              Coverage Diff              @@
##               main     #820       +/-   ##
=============================================
+ Coverage     33.94%   54.02%   +20.07%     
+ Complexity      874      854       -20     
=============================================
  Files           112      110        -2     
  Lines         42916    10559    -32357     
  Branches       9464     2000     -7464     
=============================================
- Hits          14567     5704     -8863     
+ Misses        25379     3857    -21522     
+ Partials       2970      998     -1972     

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[kazuyukitanimura]

@andygrove @comphead @huaxingao @parthchandra @viirya

[kazuyukitanimura]

Somehow Run codecov/codecov-action@v3 keeps failing, seems not related but not sure why

[andygrove]

I am now running benchmarks with this PR

[andygrove]

I ran my local TPC-DS benchmark and it doesn't show any improvement for that benchmark.

@kazuyukitanimura Do you see an improvement with any of the microbenchmark queries?

[kazuyukitanimura]

Thanks @andygrove hmmm how many iteration was used for your local benchmark?

I used q27. I will try to run some microbenchmarks to showcase...

[andygrove]

Thanks @andygrove hmmm how many iteration was used for your local benchmark?

I used q27. I will try to run some microbenchmarks to showcase...

This was the average of 3 runs for all 99 TPC-DS queries @ 100 GB scale factor

[kazuyukitanimura]

@andygrove I ran q27 30 times. The improvement is not as big as I hoped but it is improving

Before

OpenJDK 64-Bit Server VM 17.0.11+9-LTS on Mac OS X 14.6.1
Apple M1 Max
TPCDS Micro Benchmarks:                   Best Time(ms)   Avg Time(ms)   Stdev(ms)    Rate(M/s)   Per Row(ns)   Relative
------------------------------------------------------------------------------------------------------------------------
q27: Comet (Scan, Exec)                            4001           4183          98         72.5          13.8       1.0X

After

OpenJDK 64-Bit Server VM 17.0.11+9-LTS on Mac OS X 14.6.1
Apple M1 Max
TPCDS Micro Benchmarks:                   Best Time(ms)   Avg Time(ms)   Stdev(ms)    Rate(M/s)   Per Row(ns)   Relative
------------------------------------------------------------------------------------------------------------------------
q27: Comet (Scan, Exec)                            3847           4104         122         75.4          13.3       1.0X

[kazuyukitanimura]

Thanks, I realized there might be a better way to do this. Please hold merging.

[kazuyukitanimura]

opened https://github.com/apache/datafusion-comet/pull/1055 instead