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perf: Add metric for time spent casting in native scan #919

Merged
merged 5 commits into from
Sep 10, 2024
Merged

perf: Add metric for time spent casting in native scan #919

merged 5 commits into from
Sep 10, 2024

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andygrove
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@andygrove andygrove commented Sep 6, 2024 •
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Which issue does this PR close?

N/A

Rationale for this change

Make it easy to see how much of the native ScanExec time is spent casting columns to different types (this usually means unpacking dictionaries).

Example from TPC-DS q9:

Screenshot from 2024-09-06 11-57-48

DataFusion metrics in native explain output:

metrics=[
  output_rows=2097152, 
  elapsed_compute=21.847892ms, 
  cast_time=21.631731ms]

Full plan:

AggregateExec: mode=Partial, gby=[], aggr=[count, avg, avg], metrics=[output_rows=1, elapsed_compute=9.481194ms]
  ProjectionExec: expr=[col_1@1 as col_0, col_2@2 as col_1], metrics=[output_rows=400519, elapsed_compute=50.596µs]
    FilterExec: col_0@0 IS NOT NULL AND col_0@0 >= 81 AND col_0@0 <= 100, metrics=[output_rows=400519, elapsed_compute=4.753725ms]
      ScanExec: source=[CometScan parquet  (unknown)], schema=[col_0: Int32, col_1: Decimal128(7, 2), col_2: Decimal128(7, 2)], metrics=[output_rows=2097152, elapsed_compute=21.847892ms, cast_time=21.631731ms]

What changes are included in this PR?

How are these changes tested?

@andygrove andygrove marked this pull request as draft September 6, 2024 16:58
@andygrove andygrove marked this pull request as ready for review September 9, 2024 20:54
@andygrove andygrove requested review from comphead and viirya September 9, 2024 22:29
viirya
viirya reviewed Sep 9, 2024
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spark/src/main/scala/org/apache/spark/sql/comet/CometMetricNode.scala Outdated
def scanMetrics(sc: SparkContext): Map[String, SQLMetric] = {
Map(
"cast_time" ->
SQLMetrics.createNanoTimingMetric(sc, "Total time for casting arrays"))
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"arrays" in "casting arrays" may be confused with Spark array type and considered as time spent on casting (Spark) "arrays".

Maybe "casting columns"?

comphead
comphead reviewed Sep 9, 2024
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native/core/src/execution/operators/scan.rs Outdated
@@ -345,16 +347,20 @@ struct ScanStream<'a> {
baseline_metrics: BaselineMetrics,
/// Cast options
cast_options: CastOptions<'a>,
/// Timer for cast operations
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is this elapsed time?

comphead
comphead reviewed Sep 9, 2024
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spark/src/main/scala/org/apache/spark/sql/comet/CometScanExec.scala Outdated
@@ -198,9 +198,12 @@ case class CometScanExec(
// Tracking scan time has overhead, we can't afford to do it for each row, and can only do
// it for each batch.
if (supportsColumnar) {
Some("scanTime" -> SQLMetrics.createNanoTimingMetric(sparkContext, "scan time"))
Seq(
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should be it a Map instead of Seq?

@andygrove
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@viirya @comphead I have addressed feedback. Thanks.

@andygrove andygrove changed the title perf: Add native metric for time spent casting in native scan perf: Ad metric for time spent casting in native scan Sep 10, 2024
@andygrove andygrove changed the title perf: Ad metric for time spent casting in native scan perf: Add metric for time spent casting in native scan Sep 10, 2024
comphead
comphead approved these changes Sep 10, 2024
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lgtm thanks @andygrove

@andygrove andygrove merged commit c0ec49b into apache:main Sep 10, 2024
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@andygrove andygrove deleted the scan-cast-timer branch September 10, 2024 23:22
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@comphead comphead comphead approved these changes

@viirya viirya viirya approved these changes

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3 participants
@andygrove @viirya @comphead