perf: Improve conditional expression microbenchmarks

[andygrove]

Which issue does this PR close?

Closes #.

Rationale for this change

The existing benchmarks were minimal.

What changes are included in this PR?

Improvements Made

1. Improved Test Data (prepareTestTable)

• c1: Random long values (full range) - original data
• c2: Values 0-99 (ABS(value % 100)) - ensures even distribution across branches for multi-branch tests
• c3: Secondary long column (value * 2) - for non-literal result expressions
• c4: String column - for potential string result tests

2. New Benchmark Cases (8 total, up from 2)

Benchmark	Description
caseWhenLiteralBenchmark	3-branch CASE WHEN with string literal results
caseWhenManyBranchesLiteralBenchmark	10-branch CASE WHEN with string literal results
caseWhenColumnResultBenchmark	3-branch CASE WHEN with column/expression results
caseWhenManyBranchesColumnResultBenchmark	10-branch CASE WHEN with column/expression results
ifLiteralBenchmark	Simple IF with string literal results
ifColumnResultBenchmark	Simple IF with column/expression results
nestedIfBenchmark	Nested IF (4 outcomes) with string literals
nestedIfColumnResultBenchmark	Nested IF (4 outcomes) with column/expression results

3. Key Test Dimensions

• Branch count: 3 vs 10 branches (tests scalability)
• Result type: Literals vs column expressions (tests materialization overhead)
• Expression style: CASE WHEN vs IF vs nested IF

The benchmark now provides much better coverage of real-world conditional expression patterns.

How are these changes tested?

[andygrove]

OpenJDK 64-Bit Server VM 17.0.17+10-Ubuntu-122.04 on Linux 6.8.0-90-generic
AMD Ryzen 9 7950X3D 16-Core Processor
Case When Literal (3 branches):           Best Time(ms)   Avg Time(ms)   Stdev(ms)    Rate(M/s)   Per Row(ns)   Relative
------------------------------------------------------------------------------------------------------------------------
Spark                                                48             52           2         21.9          45.7       1.0X
Comet (Scan)                                         46             51           3         22.7          44.1       1.0X
Comet (Scan + Exec)                                  57             60           2         18.4          54.3       0.8X

OpenJDK 64-Bit Server VM 17.0.17+10-Ubuntu-122.04 on Linux 6.8.0-90-generic
AMD Ryzen 9 7950X3D 16-Core Processor
Case When Literal (10 branches):          Best Time(ms)   Avg Time(ms)   Stdev(ms)    Rate(M/s)   Per Row(ns)   Relative
------------------------------------------------------------------------------------------------------------------------
Spark                                                48             51           1         21.6          46.2       1.0X
Comet (Scan)                                         48             49           1         21.8          45.8       1.0X
Comet (Scan + Exec)                                  67             69           1         15.8          63.4       0.7X

OpenJDK 64-Bit Server VM 17.0.17+10-Ubuntu-122.04 on Linux 6.8.0-90-generic
AMD Ryzen 9 7950X3D 16-Core Processor
Case When Column Result (3 branches):     Best Time(ms)   Avg Time(ms)   Stdev(ms)    Rate(M/s)   Per Row(ns)   Relative
------------------------------------------------------------------------------------------------------------------------
Spark                                                37             40           1         28.0          35.7       1.0X
Comet (Scan)                                         39             42           4         26.9          37.1       1.0X
Comet (Scan + Exec)                                  45             47           3         23.6          42.4       0.8X

OpenJDK 64-Bit Server VM 17.0.17+10-Ubuntu-122.04 on Linux 6.8.0-90-generic
AMD Ryzen 9 7950X3D 16-Core Processor
Case When Column Result (10 branches):    Best Time(ms)   Avg Time(ms)   Stdev(ms)    Rate(M/s)   Per Row(ns)   Relative
------------------------------------------------------------------------------------------------------------------------
Spark                                                55             56           1         19.2          52.0       1.0X
Comet (Scan)                                         47             50           2         22.3          44.8       1.2X
Comet (Scan + Exec)                                  73             76           1         14.3          69.9       0.7X

OpenJDK 64-Bit Server VM 17.0.17+10-Ubuntu-122.04 on Linux 6.8.0-90-generic
AMD Ryzen 9 7950X3D 16-Core Processor
If Literal:                               Best Time(ms)   Avg Time(ms)   Stdev(ms)    Rate(M/s)   Per Row(ns)   Relative
------------------------------------------------------------------------------------------------------------------------
Spark                                                40             43           4         25.9          38.6       1.0X
Comet (Scan)                                         40             42           2         26.1          38.2       1.0X
Comet (Scan + Exec)                                  45             46           1         23.3          42.9       0.9X

OpenJDK 64-Bit Server VM 17.0.17+10-Ubuntu-122.04 on Linux 6.8.0-90-generic
AMD Ryzen 9 7950X3D 16-Core Processor
If Column Result:                         Best Time(ms)   Avg Time(ms)   Stdev(ms)    Rate(M/s)   Per Row(ns)   Relative
------------------------------------------------------------------------------------------------------------------------
Spark                                                33             35           1         31.8          31.4       1.0X
Comet (Scan)                                         33             35           1         31.7          31.5       1.0X
Comet (Scan + Exec)                                  39             41           2         26.8          37.3       0.8X

OpenJDK 64-Bit Server VM 17.0.17+10-Ubuntu-122.04 on Linux 6.8.0-90-generic
AMD Ryzen 9 7950X3D 16-Core Processor
Nested If Literal (4 outcomes):           Best Time(ms)   Avg Time(ms)   Stdev(ms)    Rate(M/s)   Per Row(ns)   Relative
------------------------------------------------------------------------------------------------------------------------
Spark                                                40             43           2         26.0          38.5       1.0X
Comet (Scan)                                         41             42           1         25.8          38.8       1.0X
Comet (Scan + Exec)                                  52             55           1         20.0          49.9       0.8X

OpenJDK 64-Bit Server VM 17.0.17+10-Ubuntu-122.04 on Linux 6.8.0-90-generic
AMD Ryzen 9 7950X3D 16-Core Processor
Nested If Column Result (4 outcomes):     Best Time(ms)   Avg Time(ms)   Stdev(ms)    Rate(M/s)   Per Row(ns)   Relative
------------------------------------------------------------------------------------------------------------------------
Spark                                                42             45           2         24.9          40.2       1.0X
Comet (Scan)                                         42             44           2         24.8          40.4       1.0X
Comet (Scan + Exec)                                  50             52           2         21.1          47.5       0.8X

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.55%. Comparing base (f09f8af) to head (d53ff5c).
⚠️ Report is 811 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #3024      +/-   ##
============================================
+ Coverage     56.12%   59.55%   +3.43%     
- Complexity      976     1379     +403     
============================================
  Files           119      167      +48     
  Lines         11743    15496    +3753     
  Branches       2251     2569     +318     
============================================
+ Hits           6591     9229    +2638     
- Misses         4012     4970     +958     
- Partials       1140     1297     +157     

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[mbutrovich]

Comet being slower with Exec enabled is alarming, but gotta start somewhere by measuring it. Thanks @andygrove!