Apache
/
lucene
mirror of https://github.com/apache/lucene.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Use IndexInput#prefetch for postings, skip data and impacts (#13364) 

This uses the `IndexInput#prefetch` API for postings. This relies on heuristics, as we don't know ahead of time what data we will need from a postings list:
 - Postings lists are prefetched entirely when they are short (< 16kB).
 - Impacts enums also prefetch the first page of skip data.
 - Postings enums prefetc skip data on the first call to advance().

Positions, offsets and payloads are never prefetched.

Putting the `IndexInput#prefetch` call in `TermsEnum#postings` and `TermsEnum#impacts` works well because `BooleanQuery` will first create postings/impacts enums for all clauses before it starts unioning/intersecting them. This allows the prefetching logic to run in parallel across all clauses of the same query on the same segment.
This commit is contained in:
Adrien Grand 2024-05-17 09:07:07 +02:00 committed by GitHub
parent 3d671a0fbe
commit c5331df1c4
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
1 changed files with 102 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

143
lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99PostingsReader.java
View File

@ -53,6 +53,9 @@ import org.apache.lucene.util.IOUtils;
*/
public final class Lucene99PostingsReader extends PostingsReaderBase {
/** Maximum byte size of a postings list to be fully prefetched. */
private static final int MAX_POSTINGS_SIZE_FOR_FULL_PREFETCH = 16_384;
private final IndexInput docIn;
private final IndexInput posIn;
private final IndexInput payIn;
@ -321,6 +324,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
private Lucene99SkipReader skipper;
private boolean skipped;
private boolean prefetchedSkipData;
final IndexInput startDocIn;
@ -393,7 +397,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
// lazy init
docIn = startDocIn.clone();
}
docIn.seek(docTermStartFP);
seekAndPrefetchPostings(docIn, termState);
}
doc = -1;
@ -409,6 +413,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
nextSkipDoc = BLOCK_SIZE - 1; // we won't skip if target is found in first block
docBufferUpto = BLOCK_SIZE;
skipped = false;
prefetchedSkipData = false;
return this;
}
@ -501,44 +506,52 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
public int advance(int target) throws IOException {
// current skip docID < docIDs generated from current buffer <= next skip docID
// we don't need to skip if target is buffered already
if (docFreq > BLOCK_SIZE && target > nextSkipDoc) {
if (docFreq > BLOCK_SIZE) {
if (target <= nextSkipDoc) {
// We don't need skip data yet, but we have evidence that advance() is called, so let's
// prefetch skip data in the background.
if (prefetchedSkipData == false) {
prefetchSkipData(docIn, docTermStartFP, skipOffset);
prefetchedSkipData = true;
}
} else {
if (skipper == null) {
// Lazy init: first time this enum has ever been used for skipping
skipper =
new Lucene99SkipReader(
docIn.clone(), MAX_SKIP_LEVELS, indexHasPos, indexHasOffsets, indexHasPayloads);
}
if (skipper == null) {
// Lazy init: first time this enum has ever been used for skipping
skipper =
new Lucene99SkipReader(
docIn.clone(), MAX_SKIP_LEVELS, indexHasPos, indexHasOffsets, indexHasPayloads);
if (!skipped) {
assert skipOffset != -1;
// This is the first time this enum has skipped
// since reset() was called; load the skip data:
skipper.init(docTermStartFP + skipOffset, docTermStartFP, 0, 0, docFreq);
skipped = true;
}
// always plus one to fix the result, since skip position in Lucene99SkipReader
// is a little different from MultiLevelSkipListReader
final int newDocUpto = skipper.skipTo(target) + 1;
if (newDocUpto >= blockUpto) {
// Skipper moved
assert newDocUpto % BLOCK_SIZE == 0 : "got " + newDocUpto;
blockUpto = newDocUpto;
// Force to read next block
docBufferUpto = BLOCK_SIZE;
accum = skipper.getDoc(); // actually, this is just lastSkipEntry
docIn.seek(skipper.getDocPointer()); // now point to the block we want to search
// even if freqBuffer were not read from the previous block, we will mark them as read,
// as we don't need to skip the previous block freqBuffer in refillDocs,
// as we have already positioned docIn where in needs to be.
isFreqsRead = true;
}
// next time we call advance, this is used to
// foresee whether skipper is necessary.
nextSkipDoc = skipper.getNextSkipDoc();
}
if (!skipped) {
assert skipOffset != -1;
// This is the first time this enum has skipped
// since reset() was called; load the skip data:
skipper.init(docTermStartFP + skipOffset, docTermStartFP, 0, 0, docFreq);
skipped = true;
}
// always plus one to fix the result, since skip position in Lucene99SkipReader
// is a little different from MultiLevelSkipListReader
final int newDocUpto = skipper.skipTo(target) + 1;
if (newDocUpto >= blockUpto) {
// Skipper moved
assert newDocUpto % BLOCK_SIZE == 0 : "got " + newDocUpto;
blockUpto = newDocUpto;
// Force to read next block
docBufferUpto = BLOCK_SIZE;
accum = skipper.getDoc(); // actually, this is just lastSkipEntry
docIn.seek(skipper.getDocPointer()); // now point to the block we want to search
// even if freqBuffer were not read from the previous block, we will mark them as read,
// as we don't need to skip the previous block freqBuffer in refillDocs,
// as we have already positioned docIn where in needs to be.
isFreqsRead = true;
}
// next time we call advance, this is used to
// foresee whether skipper is necessary.
nextSkipDoc = skipper.getNextSkipDoc();
}
if (docBufferUpto == BLOCK_SIZE) {
refillDocs();
@ -594,6 +607,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
private Lucene99SkipReader skipper;
private boolean skipped;
private boolean prefetchedSkipData;
final IndexInput startDocIn;
@ -715,7 +729,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
// lazy init
docIn = startDocIn.clone();
}
docIn.seek(docTermStartFP);
seekAndPrefetchPostings(docIn, termState);
}
posPendingFP = posTermStartFP;
payPendingFP = payTermStartFP;
@ -741,6 +755,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
}
docBufferUpto = BLOCK_SIZE;
skipped = false;
prefetchedSkipData = false;
return this;
}
@ -902,6 +917,13 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
payloadByteUpto = skipper.getPayloadByteUpto();
}
nextSkipDoc = skipper.getNextSkipDoc();
} else {
// We don't need skip data yet, but we have evidence that advance() is used, so prefetch it
// in the background.
if (prefetchedSkipData == false) {
prefetchSkipData(docIn, docTermStartFP, skipOffset);
prefetchedSkipData = true;
}
}
if (docBufferUpto == BLOCK_SIZE) {
refillDocs();
@ -1097,7 +1119,9 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
this.docIn = Lucene99PostingsReader.this.docIn.clone();
docFreq = termState.docFreq;
docIn.seek(termState.docStartFP);
seekAndPrefetchPostings(docIn, termState);
// Impacts almost certainly need skip data
prefetchSkipData(docIn, termState.docStartFP, termState.skipOffset);
doc = -1;
accum = 0;
@ -1318,7 +1342,8 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
posTermStartFP = termState.posStartFP;
payTermStartFP = termState.payStartFP;
totalTermFreq = termState.totalTermFreq;
docIn.seek(docTermStartFP);
seekAndPrefetchPostings(docIn, termState);
prefetchSkipData(docIn, termState.docStartFP, termState.skipOffset);
posPendingFP = posTermStartFP;
posPendingCount = 0;
if (termState.totalTermFreq < BLOCK_SIZE) {
@ -1672,7 +1697,8 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
posTermStartFP = termState.posStartFP;
payTermStartFP = termState.payStartFP;
totalTermFreq = termState.totalTermFreq;
docIn.seek(docTermStartFP);
seekAndPrefetchPostings(docIn, termState);
prefetchSkipData(docIn, termState.docStartFP, termState.skipOffset);
posPendingFP = posTermStartFP;
payPendingFP = payTermStartFP;
posPendingCount = 0;
@ -2049,6 +2075,41 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
}
}
private void seekAndPrefetchPostings(IndexInput docIn, IntBlockTermState state)
throws IOException {
if (docIn.getFilePointer() != state.docStartFP) {
// Don't prefetch if the input is already positioned at the right offset, which suggests that
// the caller is streaming the entire inverted index (e.g. for merging), let the read-ahead
// logic do its work instead. Note that this heuristic doesn't work for terms that have skip
// data, since skip data is stored after the last term, but handling all terms that have <128
// docs is a good start already.
docIn.seek(state.docStartFP);
if (state.skipOffset < 0) {
// This postings list is very short as it doesn't have skip data, prefetch the page that
// holds the first byte of the postings list.
docIn.prefetch(state.docStartFP, 1);
} else if (state.skipOffset <= MAX_POSTINGS_SIZE_FOR_FULL_PREFETCH) {
// This postings list is short as it fits on a few pages, prefetch it all, plus one byte to
// make sure to include some skip data.
docIn.prefetch(state.docStartFP, state.skipOffset + 1);
} else {
// Default case: prefetch the page that holds the first byte of postings. We'll prefetch
// skip data when we have evidence that it is used.
docIn.prefetch(state.docStartFP, 1);
}
}
// Note: we don't prefetch positions or offsets, which are less likely to be needed.
}
private void prefetchSkipData(IndexInput docIn, long docStartFP, long skipOffset)
throws IOException {
if (skipOffset > MAX_POSTINGS_SIZE_FOR_FULL_PREFETCH) {
// If skipOffset is less than this value, skip data was already prefetched when doing
// #seekAndPrefetchPostings
docIn.prefetch(docStartFP + skipOffset, 1);
}
}
@Override
public void checkIntegrity() throws IOException {
if (docIn != null) {