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Intern IndexFieldCapabilities Type String on Read #76405

Original file line number Diff line number Diff line change
@@ -11,6 +11,7 @@
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.common.io.stream.Writeable;
import org.elasticsearch.common.util.StringLiteralDeduplicator;

import java.io.IOException;
import java.util.Map;
@@ -50,7 +51,7 @@ public class IndexFieldCapabilities implements Writeable {

IndexFieldCapabilities(StreamInput in) throws IOException {
this.name = in.readString();
this.type = in.readString();
this.type = StringLiteralDeduplicator.INSTANCE.deduplicate(in.readString());
this.isMetadatafield = in.readBoolean();
this.isSearchable = in.readBoolean();
this.isAggregatable = in.readBoolean();
Original file line number Diff line number Diff line change
@@ -0,0 +1,55 @@
/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
package org.elasticsearch.common.util;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.elasticsearch.common.util.concurrent.ConcurrentCollections;

import java.util.Map;

/**
* A cache in front of Java's string interning. This method assumes that it is only called with strings that are already part of the
* JVM's string pool so that interning them does not grow the pool. Calling it with strings not in the interned string pool is not
* advisable as its performance may deteriorate to slower than outright calls to {@link String#intern()}.
*/
public final class StringLiteralDeduplicator {

private static final Logger logger = LogManager.getLogger(StringLiteralDeduplicator.class);

private static final int MAX_SIZE = 1000;
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This will start thrashing once we exceed 1000 strings. I worry about the reuse of this INSTANCE for other purposes. Can we instead make a single instance that is used solely for the field capabilities type field by making a private static instance in the IndexFieldCapabilities class? If other needs arise for this deduplicator, those would thereby be separated completely.

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++ made it a private static cache for now just limited to this class


public static final StringLiteralDeduplicator INSTANCE = new StringLiteralDeduplicator();
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private final Map<String, String> map = ConcurrentCollections.newConcurrentMapWithAggressiveConcurrency();

private StringLiteralDeduplicator() {
}

public String deduplicate(String string) {
final String res = map.get(string);
if (res != null) {
return res;
}
final String interned = string.intern();
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if (map.size() > MAX_SIZE) {
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boolean cleared = false;
synchronized (this) {
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I think exceeding the MAX_SIZE is unexpected. I would advocate not synchronizing in that case, since this runs on the transport thread and simply clear the map in all threads that enter this.

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Sure if we only use this in a limited case ++ to that, simplified as requested :)

if (map.size() > MAX_SIZE) {
map.clear();
cleared = true;
}
}
if (cleared) {
logger.debug("clearing intern cache");
}
}
map.put(interned, interned);
return interned;
}
}