fix: Dynamically adjust NestedLoopJoinProbe output batch size to prevent OOM

[zhangxffff]

What problem does this PR solve?

NestedLoopJoinProbe OOMs when build-side rows are wide (e.g., containing complex nested types like ARRAY, MAP, or large VARCHAR columns). The fixed outputBatchSize_ causes two OOM scenarios:

1. Inside NLJ: copyBuildValues() → copyRanges on nested types triggers buffer doubling that requests huge single allocations, exceeding the memory pool cap.
2. Downstream: PartialProject flattens the dictionary-wrapped probe columns via ensureFlatten, allocating numOutputRows × avgRowSize which also exceeds memory limits for large batches.

Issue Number: close #401

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 🚀 Performance improvement (optimization)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)
• 🔨 Refactoring (no logic changes)
• 🔧 Build/CI or Infrastructure changes
• 📝 Documentation only

Description

The root cause is that outputBatchSize_ is set once in the constructor via outputBatchRows() (no arguments → returns preferredOutputBatchRows) and never adjusted based on actual row size.

This PR adds dynamic batch size adjustment in:

1. prepareOutput() — pre-allocation estimate: Before creating the output vectors and before any copyBuildValues call, estimate avgRowSize from probe + build data and call outputBatchRows(avgRowSize) to compute a byte-budget-aware batch size. This prevents the first batch from OOM.

2. getOutput() — post-output refinement: After each output batch is produced, refine the batch size based on actual output->estimateFlatSize():

Performance Impact

• No Impact: This change does not affect the critical path (e.g., build system, doc, error handling).

• Positive Impact: I have run benchmarks.

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  Paste your google-benchmark or TPC-H results here.
  Before: 10.5s
  After:   8.2s  (+20%)
  

• Negative Impact: Explained below (e.g., trade-off for correctness).

Release Note

Please describe the changes in this PR

Release Note:

Release Note:
- Fixed a crash in `substr` when input is null.
- optimized `group by` performance by 20%.

Checklist (For Author)

• I have added/updated unit tests (ctest).
• I have verified the code with local build (Release/Debug).
• I have run clang-format / linters.
• (Optional) I have run Sanitizers (ASAN/TSAN) locally for complex C++ changes.
• No need to test or manual test.

Breaking Changes

• No

• Yes (Description: ...)

  Click to view Breaking Changes

  Breaking Changes:
  - Description of the breaking change.
  - Possible solutions or workarounds.
  - Any other relevant information.