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Improve positionsArrayToSelectedPositions #8624

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Jul 21, 2021
Merged

Improve positionsArrayToSelectedPositions #8624

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16 changes: 8 additions & 8 deletions core/trino-main/src/main/java/io/trino/operator/project/PageFilter.java
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Original file line number Diff line number Diff line change
Expand Up @@ -29,9 +29,9 @@ static SelectedPositions positionsArrayToSelectedPositions(boolean[] selectedPos
int selectedCount = 0;
for (int i = 0; i < size; i++) {
boolean selectedPosition = selectedPositions[i];
if (selectedPosition) {
selectedCount++;
}
// Avoid branching by casting boolean to integer.
// This improves CPU utilization by avoiding branch mispredictions.
selectedCount += selectedPosition ? 1 : 0;
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}

if (selectedCount == 0 || selectedCount == size) {
Expand All @@ -40,11 +40,11 @@ static SelectedPositions positionsArrayToSelectedPositions(boolean[] selectedPos

int[] positions = new int[selectedCount];
int index = 0;
for (int position = 0; position < size; position++) {
if (selectedPositions[position]) {
positions[index] = position;
index++;
}
for (int position = 0; index < selectedCount; position++) {
// Improve CPU utilization by avoiding setting of position conditionally.
// This improves CPU utilization by avoiding branch mispredictions.
positions[index] = position;
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index += selectedPositions[position] ? 1 : 0;
}
return SelectedPositions.positionsList(positions, 0, selectedCount);
}
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