[fix](cache stat) add builder stat to scanner (#56165)

[dataroaring]

What problem does this PR solve?

Issue Number: close #xxx

Related PR: #xxx

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[hello-stephen]

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[Copilot]

Pull request overview

This PR adds builder statistics tracking to the scanner by modifying the get_segment_num_rows method to accept and populate an OlapReaderStatistics parameter. This enables collection of file cache statistics during segment metadata loading.

Key Changes:

• Added get_segment_num_rows method to BetaRowset class with statistics parameter support
• Modified ParallelScannerBuilder to track and expose builder statistics via builder_stats() accessor
• Updated OlapScanOperator to report file cache statistics from the scanner builder to metrics and profiles

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
be/src/olap/rowset/beta_rowset.h	Added get_segment_num_rows method declaration and member variables for caching segment rows using thread-safe DorisCallOnce pattern
be/src/olap/rowset/beta_rowset.cpp	Implemented get_segment_num_rows method with lazy initialization of segment row counts and statistics tracking
be/src/olap/rowset/beta_rowset_reader.cpp	Refactored to call BetaRowset::get_segment_num_rows instead of accessing internal state directly
be/src/olap/parallel_scanner_builder.h	Added _builder_stats member and builder_stats() accessor method
be/src/olap/parallel_scanner_builder.cpp	Updated to use new get_segment_num_rows API and pass statistics parameter
be/src/pipeline/exec/olap_scan_operator.cpp	Added file cache profile reporting and metrics updates from builder statistics
be/test/olap/segcompaction_test.cpp	Updated test calls to use new BetaRowset::get_segment_num_rows API with statistics parameter
be/test/olap/segcompaction_mow_test.cpp	Updated test calls to use new BetaRowset::get_segment_num_rows API with statistics parameter
be/test/olap/rowid_conversion_test.cpp	Updated test calls to use new BetaRowset::get_segment_num_rows API with statistics parameter

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[Copilot]

The method call custom_profile() appears to be undefined. Looking at the surrounding code in this file, profile counters are typically added to _runtime_profile, _scanner_profile, or _segment_profile. The method custom_profile() is not defined in the base classes (PipelineXLocalStateBase, ScanLocalState, etc.) and this will likely cause a compilation error. This should probably be _runtime_profile instead to match the pattern used in line 69 and elsewhere in the codebase.

Suggested change

	_scan_rows = ADD_COUNTER(custom_profile(), "ScanRows", TUnit::UNIT);
	_scan_rows = ADD_COUNTER(_runtime_profile, "ScanRows", TUnit::UNIT);

[dataroaring]

run buildall