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Speed up IndexedDISI Sparse #AdvanceExactWithinBlock for tiny step advance #12324

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merged 4 commits into from
Jun 13, 2023
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Speed up IndexedDISI Sparse #AdvanceExactWithinBlock for tiny step advance #12324

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6a791d7
cache sparse next doc
gf2121 May 22, 2023
7ddde17
add CHANGES
gf2121 May 22, 2023
31c7c12
feedback fix: remove integer.max_value
gf2121 Jun 1, 2023
3823a25
feedback fix: 65536->BLOCK_SIZE
gf2121 Jun 2, 2023
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2 changes: 2 additions & 0 deletions lucene/CHANGES.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -131,6 +131,8 @@ Improvements
Optimizations
---------------------

* GITHUB#12324: Speed up Sparse block advanceExact with tiny step in IndexedDISI. (Guo Feng)

* GITHUB#12270 Don't generate stacktrace in CollectionTerminatedException. (Armin Braun)

* GITHUB#12286 Toposort use iterator to avoid stackoverflow. (Tang Donghai)
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13 changes: 12 additions & 1 deletion lucene/core/src/java/org/apache/lucene/codecs/lucene90/IndexedDISI.java
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Expand Up @@ -418,6 +418,7 @@ public static RandomAccessInput createJumpTable(

// SPARSE variables
boolean exists;
int nextExistDocInBlock = -1;
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// DENSE variables
long word;
Expand Down Expand Up @@ -495,6 +496,7 @@ private void readBlockHeader() throws IOException {
if (numValues <= MAX_ARRAY_LENGTH) {
method = Method.SPARSE;
blockEnd = slice.getFilePointer() + (numValues << 1);
nextExistDocInBlock = -1;
} else if (numValues == 65536) {
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Can we change this to BLOCK_SIZE just by the way?

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@gf2121 gf2121 Jun 1, 2023 •
edited
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Sorry, I'm not sure i've got your point. Do you mean change to nextExistDocInBlock = BLOCK_SIZE; ?
I think that will make SPARSE$advanceExact always return false.

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Oh sorry I (perhaps github webpage as well :)) didn't make it clear: I want to change 65536 to BLOCK_SIZE.
(Actually later on I found there's several more 65536 in this file, would you like to do a batch replacement?)

method = Method.ALL;
blockEnd = slice.getFilePointer();
Expand Down Expand Up @@ -550,32 +552,41 @@ boolean advanceWithinBlock(IndexedDISI disi, int target) throws IOException {
if (doc >= targetInBlock) {
disi.doc = disi.block | doc;
disi.exists = true;
disi.nextExistDocInBlock = doc;
return true;
}
}
disi.nextExistDocInBlock = Integer.MAX_VALUE;
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nit: I actually wonder whether we really need to set it to MAX_VALUE here (and below) since the next advance within the same block would be prevented by disi.index anyway. But set it to MAX_VALUE does no harm as well.

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Oh yes! disi.index should be enough :)

return false;
}

@Override
boolean advanceExactWithinBlock(IndexedDISI disi, int target) throws IOException {
final int targetInBlock = target & 0xFFFF;
// TODO: binary search
if (disi.nextExistDocInBlock > targetInBlock) {
assert !disi.exists;
return false;
}
if (target == disi.doc) {
return disi.exists;
}
for (; disi.index < disi.nextBlockIndex; ) {
int doc = Short.toUnsignedInt(disi.slice.readShort());
disi.index++;
if (doc >= targetInBlock) {
disi.nextExistDocInBlock = doc;
if (doc != targetInBlock) {
disi.index--;
disi.slice.seek(disi.slice.getFilePointer() - Short.BYTES);
break;
disi.exists = false;
return false;
}
disi.exists = true;
return true;
}
}
disi.nextExistDocInBlock = Integer.MAX_VALUE;
disi.exists = false;
return false;
}
Expand Down