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Optimize first_value and last_value functions with IGNORE NULLS #22092

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Merged
merged 1 commit into from
Jun 3, 2024
Merged

Optimize first_value and last_value functions with IGNORE NULLS #22092

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77 changes: 67 additions & 10 deletions core/trino-main/src/main/java/io/trino/operator/window/FirstValueFunction.java
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Original file line number Diff line number Diff line change
Expand Up @@ -28,37 +28,94 @@ public class FirstValueFunction
private final int argumentChannel;
private final boolean ignoreNulls;

// Record a frame start with corresponding first non-null position
// or last seen null position.
// The non-null position is valid for all frames starting from the recorded frame start or later,
// and ending at the recorded non-null position or later.
private int recordedFrameStart = -1;
private int recordedValuePosition = -1;
private int recordedNullPosition = -1;

public FirstValueFunction(List<Integer> argumentChannels, boolean ignoreNulls)
{
this.argumentChannel = getOnlyElement(argumentChannels);
this.ignoreNulls = ignoreNulls;
}

@Override
public void reset()
{
recordedFrameStart = -1;
recordedValuePosition = -1;
recordedNullPosition = -1;
}

@Override
public void processRow(BlockBuilder output, int frameStart, int frameEnd, int currentPosition)
{
// empty frame
if (frameStart < 0) {
output.appendNull();
return;
}

int valuePosition = frameStart;
if (!ignoreNulls) {
windowIndex.appendTo(argumentChannel, frameStart, output);
return;
}

if (ignoreNulls) {
while (valuePosition >= 0 && valuePosition <= frameEnd) {
if (!windowIndex.isNull(argumentChannel, valuePosition)) {
break;
if (recordedFrameStart >= 0 && frameStart >= recordedFrameStart) {
// try to use the recorded non-null position
if (recordedValuePosition >= 0 && frameStart <= recordedValuePosition) {
if (frameEnd < recordedValuePosition) {
// only nulls in the frame
output.appendNull();
return;
}
// use the recorded non-null position
windowIndex.appendTo(argumentChannel, recordedValuePosition, output);
return;
}
// try to use the recorded null position
if (recordedNullPosition >= 0 && frameStart <= recordedNullPosition) {
if (frameEnd <= recordedNullPosition) {
// only nulls in the frame
output.appendNull();
return;
}

valuePosition++;
}
}

if (valuePosition > frameEnd) {
output.appendNull();
return;
// there is no recorded position or the current frame is before / after the recorded frame
// find the first non-null or last null position for current the frame and record it for future reference
// try to optimize by using the recorded null position
int valuePosition;
if (recordedFrameStart >= 0 && recordedNullPosition >= 0 && frameStart >= recordedFrameStart && frameStart <= recordedNullPosition) {
valuePosition = recordedNullPosition;
}
else {
valuePosition = frameStart;
}

recordedFrameStart = frameStart;
recordedValuePosition = -1;
recordedNullPosition = -1;

while (valuePosition >= 0 && valuePosition <= frameEnd) {
if (!windowIndex.isNull(argumentChannel, valuePosition)) {
break;
}

valuePosition++;
}

if (valuePosition > frameEnd) {
recordedNullPosition = frameEnd;
output.appendNull();
return;
}

recordedValuePosition = valuePosition;
windowIndex.appendTo(argumentChannel, valuePosition, output);
}
}
77 changes: 67 additions & 10 deletions core/trino-main/src/main/java/io/trino/operator/window/LastValueFunction.java
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Original file line number Diff line number Diff line change
Expand Up @@ -28,37 +28,94 @@ public class LastValueFunction
private final int argumentChannel;
private final boolean ignoreNulls;

// Record a frame end with corresponding first non-null position
// or last seen null position (going backwards).
// The non-null position is valid for all frames starting from the recorded non-null position or before
// and ending at the recorded frame end or before.
private int recordedFrameEnd = -1;
private int recordedValuePosition = -1;
private int recordedNullPosition = -1;

public LastValueFunction(List<Integer> argumentChannels, boolean ignoreNulls)
{
this.argumentChannel = getOnlyElement(argumentChannels);
this.ignoreNulls = ignoreNulls;
}

@Override
public void reset()
{
recordedFrameEnd = -1;
recordedValuePosition = -1;
recordedNullPosition = -1;
}

@Override
public void processRow(BlockBuilder output, int frameStart, int frameEnd, int currentPosition)
{
// empty frame
if (frameStart < 0) {
output.appendNull();
return;
}

int valuePosition = frameEnd;
if (!ignoreNulls) {
windowIndex.appendTo(argumentChannel, frameEnd, output);
return;
}

if (ignoreNulls) {
while (valuePosition >= frameStart) {
if (!windowIndex.isNull(argumentChannel, valuePosition)) {
break;
if (recordedFrameEnd >= 0 && frameEnd <= recordedFrameEnd) {
// try to use the recorded non-null position
if (recordedValuePosition >= 0 && frameEnd >= recordedValuePosition) {
if (frameStart > recordedValuePosition) {
// only nulls in the frame
output.appendNull();
return;
}
// use the recorded non-null position
windowIndex.appendTo(argumentChannel, recordedValuePosition, output);
return;
}
// try to use the recorded null position
if (recordedNullPosition >= 0 && frameEnd >= recordedNullPosition) {
if (frameStart >= recordedNullPosition) {
// only nulls in the frame
output.appendNull();
return;
}

valuePosition--;
}
}

if (valuePosition < frameStart) {
output.appendNull();
return;
// there is no recorded position or the current frame is before / after the recorded frame
// find the first non-null or last null position for current the frame and record it for future reference
// try to optimize by using the recorded null position
int valuePosition;
if (recordedFrameEnd >= 0 && recordedNullPosition >= 0 && frameEnd <= recordedFrameEnd && frameEnd >= recordedNullPosition) {
valuePosition = recordedNullPosition;
}
else {
valuePosition = frameEnd;
}

recordedFrameEnd = frameEnd;
recordedValuePosition = -1;
recordedNullPosition = -1;

while (valuePosition >= frameStart) {
if (!windowIndex.isNull(argumentChannel, valuePosition)) {
break;
}

valuePosition--;
}

if (valuePosition < frameStart) {
recordedNullPosition = frameStart;
output.appendNull();
return;
}

recordedValuePosition = valuePosition;
windowIndex.appendTo(argumentChannel, valuePosition, output);
}
}