feat(native): Split IndexLookupJoin stats for IndexSource

[zacw7]

IndexLookupJoin embeds IndexSource as a single Velox operator, but Presto's plan has them as two separate logical plan nodes. This change expands IndexLookupJoin's operator stats using its StatsSplitter so that the Presto coordinator sees stats for both plan nodes.

== NO RELEASE NOTE ==

Summary by Sourcery

Enhancements:

• Add expansion of IndexLookupJoin operator stats using its StatsSplitter so that embedded IndexSource statistics are reported as separate plan node metrics to the Presto coordinator.

[sourcery-ai]

Reviewer's Guide

Adds an expansion step for operator stats so that IndexLookupJoin, which embeds IndexSource, reports separate stats entries corresponding to Presto’s logical plan nodes.

Class diagram for OperatorStats and expandOperatorStats

classDiagram
  class OperatorStats {
    +string operatorType
    +optional StatsSplitter statsSplitter
  }

  class StatsSplitter {
    +vector~OperatorStats~ operator() (OperatorStats opStats)
  }

  class PrestoTaskHelpers {
    +vector~OperatorStats~ expandOperatorStats(vector~OperatorStats~ operatorStats)
  }

  OperatorStats --> StatsSplitter : uses
  PrestoTaskHelpers ..> OperatorStats : processes
  PrestoTaskHelpers ..> StatsSplitter : invokes when
  note for PrestoTaskHelpers "expandOperatorStats expands IndexLookupJoin stats into multiple OperatorStats entries, including a separate one for IndexSource"

Loading

File-Level Changes

Change	Details	Files
Introduce an operator-stats expansion helper so IndexLookupJoin emits separate stats for its embedded IndexSource logical node.	Add expandOperatorStats helper that iterates over collected OperatorStats and conditionally expands IndexLookupJoin using its statsSplitter functor when present Reserve capacity in the expanded stats vector based on the original operator stats size to avoid reallocations Preserve existing operator stats behavior for all operators other than IndexLookupJoin by passing them through unchanged	presto-native-execution/presto_cpp/main/PrestoTask.cpp

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[sourcery-ai]

Hey - I've reviewed your changes and they look great!

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[tanjialiang]

Are there followups for this PR? Maybe some comments on this one:

• should we add tests to this utility?
• how is this method used? the PR does not show its callsite.

[tanjialiang]

Thanks LGTM

[xiaoxmeng]

@zacw7 LGTM % use split to be consistent in naming as in Velox? Thanks!