Add UnionArray compute functions

[connortsui20]

Rationale for this change

Depends on #8834. Tracking issue: #8769.

This is the deferred compute layer for UnionArray and remains a draft for later review.

What changes are included in this PR?

• Adds UnionArray filter, take, slice, and mask execution.
• Adds constant and chunked canonicalization.
• Adds Union casting, uncompressed-size accounting, and recursive compression.
• Adds focused tests for structural operations and canonicalization.

Nullable-index take remains explicitly unsupported and needs resolution before this layer is ready.

What APIs are changed? Are there any user-facing changes?

No additional public array representation APIs beyond #8834. This layer wires UnionArray into existing compute paths.

[github-actions]

Polar Signals Profiling Results

Latest Run

Status	Commit	Job	Attempt	Link
🟢 Done	ec92eef		1	Explore Profiling Data

Previous Runs (7)

Status	Commit	Job	Attempt	Link
🟢 Done	ab33ec0		1	Explore Profiling Data
🟢 Done	f2427ce		1	Explore Profiling Data
🟢 Done	e32db9e		1	Explore Profiling Data
🟢 Done	98f8f06		1	Explore Profiling Data
🟢 Done	1e867dd		1	Explore Profiling Data
🟢 Done	a6b7e6c		1	Explore Profiling Data
🟢 Done	6fe53ba		1	Explore Profiling Data

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Powered by Polar Signals Cloud

[github-actions]

Benchmarks: Vortex queries 📖

Verdict: No clear signal (low confidence)
Attributed Vortex impact: +1.2%
Engines: DataFusion No clear signal (+4.0%, low confidence) · DuckDB No clear signal (-1.5%, low confidence)
Vortex (geomean): 1.014x ➖
Parquet (geomean): 1.008x ➖
Shifts: Parquet (control) +0.8% · Median polish +0.8%

How to read Verdict and Engines

• Verdict: Overall PR-level signal after subtracting baseline drift estimated from Parquet control rows. It can be Likely improvement, Likely regression, or No clear signal.
• Engines: Per-engine attribution. DataFusion is compared against DataFusion/Parquet controls; DuckDB is compared against DuckDB/Parquet controls. This answers whether each engine improved or regressed independently.
• Confidence: Based on directional consistency, share of rows above the noise floor, and control-run noise.

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datafusion / vortex-file-compressed (1.045x ➖, 0↑ 0↓)

name	PR ec92eef (ns)	base 57962f4 (ns)	ratio (PR/base)
vortex_q00/datafusion:vortex-file-compressed	8414693	8197567	1.03
vortex_q01/datafusion:vortex-file-compressed	5201551	4885078	1.06

datafusion / parquet (1.006x ➖, 0↑ 0↓)

name	PR ec92eef (ns)	base 57962f4 (ns)	ratio (PR/base)
vortex_q00/datafusion:parquet	20201445	20638806	0.98
vortex_q01/datafusion:parquet	4731033	4580085	1.03

duckdb / vortex-file-compressed (0.996x ➖, 0↑ 0↓)

name	PR ec92eef (ns)	base 57962f4 (ns)	ratio (PR/base)
vortex_q00/duckdb:vortex-file-compressed	9982079	10061599	0.99
vortex_q01/duckdb:vortex-file-compressed	6163313	6167184	1.00

duckdb / parquet (1.010x ➖, 0↑ 0↓)

name	PR ec92eef (ns)	base 57962f4 (ns)	ratio (PR/base)
vortex_q00/duckdb:parquet	23447372	23195009	1.01
vortex_q01/duckdb:parquet	9434025	9340266	1.01

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No file size changes detected.

[codspeed-hq]

Merging this PR will improve performance by 28.39%

⚡ 1 improved benchmark
✅ 1846 untouched benchmarks
⏩ 46 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	decode_varbin[(1000, 8)]	34.3 µs	26.7 µs	+28.39%

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing ct/union-array-compute (ec92eef) with ct/union-array (772b738)²}

Footnotes

1. 46 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on ct/union-array (f51f2dd) during the generation of this report, so 8307911 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[codecov]

Codecov Report

❌ Patch coverage is 74.09910% with 115 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.13%. Comparing base (cd92358) to head (98f8f06).

Files with missing lines	Patch %	Lines
...rtex-array/src/arrays/constant/vtable/canonical.rs	49.42%	44 Missing ⚠️
vortex-array/src/scalar_fn/fns/cast/mod.rs	0.00%	17 Missing ⚠️
vortex-array/src/arrays/union/tests.rs	93.59%	13 Missing ⚠️
...gregate_fn/fns/uncompressed_size_in_bytes/union.rs	0.00%	11 Missing ⚠️
vortex-array/src/arrays/masked/execute.rs	0.00%	10 Missing ⚠️
vortex-compressor/src/compressor/cascade.rs	0.00%	8 Missing ⚠️
vortex-array/src/arrays/filter/execute/mod.rs	0.00%	6 Missing ⚠️
vortex-array/src/arrays/dict/execute.rs	0.00%	3 Missing ⚠️
...aggregate_fn/fns/uncompressed_size_in_bytes/mod.rs	0.00%	1 Missing ⚠️
...ortex-array/src/arrays/chunked/vtable/canonical.rs	97.14%	1 Missing ⚠️
... and 1 more

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