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Speed up ordinal lookups in composite aggregation #78313

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Oct 6, 2021
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Speed up ordinal lookups in composite aggregation #78313

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6c2744b
Speed up ordinal lookups in composte aggregation
jimczi Sep 27, 2021
18ee058
apply review comments
jimczi Sep 27, 2021
f54398f
remove noop if
jimczi Sep 27, 2021
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145 changes: 101 additions & 44 deletions ...main/java/org/elasticsearch/search/aggregations/bucket/composite/OrdinalValuesSource.java
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,12 @@
import org.elasticsearch.search.aggregations.LeafBucketCollector;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.LongConsumer;

import static org.apache.lucene.index.SortedSetDocValues.NO_MORE_ORDS;
Expand All @@ -50,6 +56,9 @@ class OrdinalValuesSource extends SingleDimensionValuesSource<BytesRef> {
private final LongConsumer breakerConsumer; // track how much bytes are stored in the values array
private final CheckedFunction<LeafReaderContext, SortedSetDocValues, IOException> docValuesFunc;

// doc-values lookup, cached by LeafReaderContext ordinal
private final Map<Integer, SortedSetDocValues> dvsLookup = new HashMap<>();

private SortedSetDocValues lookup; // current ordinals lookup
private int leafReaderOrd = -1; // current LeafReaderContext ordinal

Expand Down Expand Up @@ -245,22 +254,32 @@ BytesRef toComparable(int slot) throws IOException {
LeafBucketCollector getLeafCollector(LeafReaderContext context, LeafBucketCollector next) throws IOException {
final boolean leafReaderContextChanged = context.ord != leafReaderOrd;
assert leafReaderContextChanged == false || invariant(); // for performance reasons only check invariant upon change
final SortedSetDocValues dvs = docValuesFunc.apply(context);
if (leafReaderContextChanged) {
remapOrdinals(lookup, dvs);
// use a separate instance for ordinal and term lookups, that is cached per segment
// to speed up sorted collections that call getLeafCollector once per term (see above)
final SortedSetDocValues newLookup = dvsLookup.computeIfAbsent(context.ord, k -> {
try {
return docValuesFunc.apply(context);
} catch (IOException e) {
throw new UncheckedIOException(e);
}
});
remapOrdinals(lookup, newLookup);
lookup = newLookup;
leafReaderOrd = context.ord;
}
lookup = dvs;

// and creates a SortedSetDocValues to iterate over the values
final SortedSetDocValues it = docValuesFunc.apply(context);
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assert leafReaderContextChanged == false || invariant(); // for performance reasons only check invariant upon change
return new LeafBucketCollector() {
@Override
public void collect(int doc, long bucket) throws IOException {
// caller of getLeafCollector ensures that collection happens before requesting a new leaf collector
// this is important as ordinals only make sense in the context of the current lookup
assert dvs == lookup;
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we could still assert that they have same leaf reader context ordinal? i.e. that the ordinal-based operations here make sense.

if (dvs.advanceExact(doc)) {
if (it.advanceExact(doc)) {
long ord;
while ((ord = dvs.nextOrd()) != NO_MORE_ORDS) {
while ((ord = it.nextOrd()) != NO_MORE_ORDS) {
currentValueOrd = ord;
currentValueUnmapped = null;
next.collect(doc, bucket);
Expand All @@ -283,63 +302,101 @@ LeafBucketCollector getLeafCollector(Comparable<BytesRef> value, LeafReaderConte
throw new IllegalArgumentException("Expected BytesRef, got " + value.getClass());
}
BytesRef term = (BytesRef) value;
final SortedSetDocValues dvs = docValuesFunc.apply(context);
if (leafReaderContextChanged) {
remapOrdinals(lookup, dvs);
leafReaderOrd = context.ord;
// use a separate instance for ordinal and term lookups, that is cached per segment
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This comment isn't right for this method. Here, after your refactoring, we don't have a separate instance as there is no iteration anymore.

// to speed up sorted collections that call getLeafCollector once per term
final SortedSetDocValues newLookup = dvsLookup.computeIfAbsent(context.ord, k -> {
try {
return docValuesFunc.apply(context);
} catch (IOException e) {
throw new UncheckedIOException(e);
}
});
remapOrdinals(lookup, newLookup);
lookup = newLookup;
}
lookup = dvs;
currentValueOrd = lookup.lookupTerm(term);
currentValueUnmapped = null;
leafReaderOrd = context.ord;
assert currentValueOrd >= 0;
assert leafReaderContextChanged == false || invariant(); // for performance reasons only check invariant upon change
return new LeafBucketCollector() {
boolean currentValueIsSet = false;
return next;
}

@Override
public void collect(int doc, long bucket) throws IOException {
// caller of getLeafCollector ensures that collection happens before requesting a new leaf collector
// this is important as ordinals only make sense in the context of the current lookup
assert dvs == lookup;
if (currentValueIsSet == false) {
if (dvs.advanceExact(doc)) {
long ord;
while ((ord = dvs.nextOrd()) != NO_MORE_ORDS) {
if (term.equals(dvs.lookupOrd(ord))) {
currentValueIsSet = true;
currentValueOrd = ord;
currentValueUnmapped = null;
break;
}
}
}
}
assert currentValueIsSet;
next.collect(doc, bucket);
private static class Slot implements Comparable<Slot> {
final int index;
final long ord;
final BytesRef unmapped;

private Slot(int index, long ord, BytesRef unmapped) {
assert ord >= 0 || unmapped != null;
this.index = index;
this.ord = ord;
this.unmapped = unmapped;
}

@Override
public int compareTo(Slot other) {
if (ord < 0 && ord == other.ord) {
assert unmapped != null && other.unmapped != null;
// compare by original term if both ordinals are insertion points (negative value)
return unmapped.compareTo(other.unmapped);
}
};
long norm1 = ord < 0 ? -ord - 1 : ord;
long norm2 = other.ord < 0 ? -other.ord - 1 : other.ord;
int cmp = Long.compare(norm1, norm2);
return cmp == 0 ? Long.compare(ord, other.ord) : cmp;
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}
}

/**
* Remaps ordinals when switching LeafReaders. It's possible that a term is not mapped for the new LeafReader,
* in that case remember the term so that future remapping steps can accurately be done.
*/
private void remapOrdinals(SortedSetDocValues oldMapping, SortedSetDocValues newMapping) throws IOException {
// speed up the lookups by sorting ordinals first
List<Slot> sorted = new ArrayList<>();
for (int i = 0; i < numSlots; i++) {
final long oldOrd = valuesOrd.get(i);
if (oldOrd != Long.MIN_VALUE) {
final long newOrd;
if (oldOrd >= 0) {
final BytesRef newVal = oldMapping.lookupOrd(oldOrd);
newOrd = newMapping.lookupTerm(newVal);
long ord = valuesOrd.get(i);
if (ord != Long.MIN_VALUE) {
sorted.add(new Slot(i, ord, ord < 0 ? valuesUnmapped.get(i) : null));
}
}
Collections.sort(sorted);

long lastOldOrd = Long.MIN_VALUE;
long lastNewOrd = Long.MIN_VALUE;
BytesRef lastUnmapped = null;
for (Slot slot : sorted) {
final long index = slot.index;
final long oldOrd = slot.ord;
final BytesRef unmapped = slot.unmapped;
final long newOrd;
if (oldOrd >= 0) {
if (lastOldOrd == oldOrd) {
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newOrd = lastNewOrd;
if (newOrd < 0) {
setValueWithBreaking(i, BytesRef.deepCopyOf(newVal));
setValueWithBreaking(index, lastUnmapped);
}
} else {
newOrd = newMapping.lookupTerm(valuesUnmapped.get(i));
if (newOrd >= 0) {
setValueWithBreaking(i, null);
final BytesRef newVal = oldMapping.lookupOrd(oldOrd);
newOrd = newMapping.lookupTerm(newVal);
if (newOrd < 0) {
setValueWithBreaking(index, BytesRef.deepCopyOf(newVal));
}
}
valuesOrd.set(i, newOrd);
} else {
// the original term is missing in the dictionary
assert unmapped != null;
newOrd = newMapping.lookupTerm(unmapped);
if (newOrd >= 0) {
setValueWithBreaking(index, null);
}
}
lastOldOrd = oldOrd;
lastNewOrd = newOrd;
lastUnmapped = valuesUnmapped.get(index);
valuesOrd.set(index, newOrd);
}

if (currentValueOrd != null) {
Expand Down
11 changes: 9 additions & 2 deletions ...java/org/elasticsearch/search/aggregations/bucket/composite/CompositeAggregatorTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.index.NoMergePolicy;
import org.apache.lucene.index.RandomIndexWriter;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.DocValuesFieldExistsQuery;
Expand Down Expand Up @@ -2836,17 +2837,23 @@ private void executeTestCase(
config.setIndexSort(indexSort);
config.setCodec(TestUtil.getDefaultCodec());
}
if (forceMerge == false) {
config.setMergePolicy(NoMergePolicy.INSTANCE);
}
try (RandomIndexWriter indexWriter = new RandomIndexWriter(random(), directory, config)) {
Document document = new Document();
int id = 0;
for (Map<String, List<Object>> fields : dataset) {
document.clear();
addToDocument(id, document, fields);
indexWriter.addDocument(document);
if (frequently()) {
indexWriter.commit();
}
id++;
}
if (forceMerge || rarely()) {
// forceMerge randomly or if the collector-per-leaf testing stuff would break the tests.
if (forceMerge) {
// forceMerge if the collector-per-leaf testing stuff would break the tests.
indexWriter.forceMerge(1);
} else {
if (dataset.size() > 0) {
Expand Down