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* the Apache License, Version 2.0 (the "License"); you may
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* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
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package org.elasticsearch.index.shard;
import org.apache.lucene.index.CodecReader;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.MergePolicy;
import org.apache.lucene.index.MergeTrigger;
import org.apache.lucene.index.SegmentCommitInfo;
import org.apache.lucene.index.SegmentInfos;
import org.apache.lucene.store.Directory;
import org.elasticsearch.Version;
import org.elasticsearch.common.logging.ESLogger;
import org.elasticsearch.common.logging.Loggers;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
/**
* A {@link MergePolicy} that upgrades segments and can upgrade merges.
*
* It can be useful to use the background merging process to upgrade segments,
* for example when we perform internal changes that imply different index
* options or when a user modifies his mapping in non-breaking ways: we could
* imagine using this merge policy to be able to add doc values to fields after
* the fact or on the opposite to remove them.
*
* For now, this {@link MergePolicy} takes care of moving versions that used to
* be stored as payloads to numeric doc values.
*/
public final class ElasticsearchMergePolicy extends MergePolicy {
private static ESLogger logger = Loggers.getLogger(ElasticsearchMergePolicy.class);
private final MergePolicy delegate;
// True if the next merge request should do segment upgrades:
private volatile boolean upgradeInProgress;
// True if the next merge request should only upgrade ancient (an older Lucene major version than current) segments;
private volatile boolean upgradeOnlyAncientSegments;
private static final int MAX_CONCURRENT_UPGRADE_MERGES = 5;
/** @param delegate the merge policy to wrap */
public ElasticsearchMergePolicy(MergePolicy delegate) {
this.delegate = delegate;
}
/** Return an "upgraded" view of the reader. */
static CodecReader filter(CodecReader reader) throws IOException {
// convert 0.90.x _uid payloads to _version docvalues if needed
reader = VersionFieldUpgrader.wrap(reader);
// TODO: remove 0.90.x/1.x freqs/prox/payloads from _uid?
// the previous code never did this, so some indexes carry around trash.
return reader;
}
static class IndexUpgraderOneMerge extends OneMerge {
public IndexUpgraderOneMerge(List segments) {
super(segments);
}
@Override
public List getMergeReaders() throws IOException {
final List newReaders = new ArrayList<>();
for (CodecReader reader : super.getMergeReaders()) {
newReaders.add(filter(reader));
}
return newReaders;
}
}
static class IndexUpgraderMergeSpecification extends MergeSpecification {
@Override
public void add(OneMerge merge) {
super.add(new IndexUpgraderOneMerge(merge.segments));
}
@Override
public String segString(Directory dir) {
return "IndexUpgraderMergeSpec[" + super.segString(dir) + "]";
}
}
static MergeSpecification upgradedMergeSpecification(MergeSpecification spec) {
if (spec == null) {
return null;
}
MergeSpecification upgradedSpec = new IndexUpgraderMergeSpecification();
for (OneMerge merge : spec.merges) {
upgradedSpec.add(merge);
}
return upgradedSpec;
}
@Override
public MergeSpecification findMerges(MergeTrigger mergeTrigger,
SegmentInfos segmentInfos, IndexWriter writer) throws IOException {
return upgradedMergeSpecification(delegate.findMerges(mergeTrigger, segmentInfos, writer));
}
private boolean shouldUpgrade(SegmentCommitInfo info) {
org.apache.lucene.util.Version old = info.info.getVersion();
org.apache.lucene.util.Version cur = Version.CURRENT.luceneVersion;
// Something seriously wrong if this trips:
assert old.major <= cur.major;
if (cur.major > old.major) {
// Always upgrade segment if Lucene's major version is too old
return true;
}
if (upgradeOnlyAncientSegments == false && cur.minor > old.minor) {
// If it's only a minor version difference, and we are not upgrading only ancient segments,
// also upgrade:
return true;
}
// Version matches, or segment is not ancient and we are only upgrading ancient segments:
return false;
}
@Override
public MergeSpecification findForcedMerges(SegmentInfos segmentInfos,
int maxSegmentCount, Map segmentsToMerge, IndexWriter writer)
throws IOException {
if (upgradeInProgress) {
MergeSpecification spec = new IndexUpgraderMergeSpecification();
for (SegmentCommitInfo info : segmentInfos) {
if (shouldUpgrade(info)) {
// TODO: Use IndexUpgradeMergePolicy instead. We should be comparing codecs,
// for now we just assume every minor upgrade has a new format.
logger.debug("Adding segment " + info.info.name + " to be upgraded");
spec.add(new OneMerge(Collections.singletonList(info)));
}
// TODO: we could check IndexWriter.getMergingSegments and avoid adding merges that IW will just reject?
if (spec.merges.size() == MAX_CONCURRENT_UPGRADE_MERGES) {
// hit our max upgrades, so return the spec. we will get a cascaded call to continue.
logger.debug("Returning " + spec.merges.size() + " merges for upgrade");
return spec;
}
}
// We must have less than our max upgrade merges, so the next return will be our last in upgrading mode.
if (spec.merges.isEmpty() == false) {
logger.debug("Returning " + spec.merges.size() + " merges for end of upgrade");
return spec;
}
// Only set this once there are 0 segments needing upgrading, because when we return a
// spec, IndexWriter may (silently!) reject that merge if some of the segments we asked
// to be merged were already being (naturally) merged:
upgradeInProgress = false;
// fall through, so when we don't have any segments to upgrade, the delegate policy
// has a chance to decide what to do (e.g. collapse the segments to satisfy maxSegmentCount)
}
return upgradedMergeSpecification(delegate.findForcedMerges(segmentInfos, maxSegmentCount, segmentsToMerge, writer));
}
@Override
public MergeSpecification findForcedDeletesMerges(SegmentInfos segmentInfos, IndexWriter writer)
throws IOException {
return upgradedMergeSpecification(delegate.findForcedDeletesMerges(segmentInfos, writer));
}
@Override
public boolean useCompoundFile(SegmentInfos segments, SegmentCommitInfo newSegment, IndexWriter writer) throws IOException {
return delegate.useCompoundFile(segments, newSegment, writer);
}
/**
* When upgrade is true, running a force merge will upgrade any segments written
* with older versions. This will apply to the next call to
* {@link IndexWriter#forceMerge} that is handled by this {@link MergePolicy}, as well as
* cascading calls made by {@link IndexWriter}.
*/
public void setUpgradeInProgress(boolean upgrade, boolean onlyAncientSegments) {
this.upgradeInProgress = upgrade;
this.upgradeOnlyAncientSegments = onlyAncientSegments;
}
@Override
public String toString() {
return getClass().getSimpleName() + "(" + delegate + ")";
}
}