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Make the default ReadAdvice configurable by sysprop (#13264)

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Uwe Schindler 2024-04-04 18:42:31 +02:00 committed by GitHub
parent 4ea2bae119
commit f7db975fc4
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3 changed files with 26 additions and 7 deletions
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6
lucene/CHANGES.txt
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@ -163,9 +163,11 @@ Bug Fixes
Changes in Runtime Behavior
---------------------
* GITHUB#13244: IOContext now uses ReadAdvice#RANDOM by default for read
* GITHUB#13244, GITHUB#13264: IOContext now uses ReadAdvice#RANDOM by default for read
operations. An implication is that `MMapDirectory` will use POSIX_MADV_RANDOM
on POSIX systems. (Adrien Grand)
on POSIX systems. To fallback to OS default behaviour, pass system property via
`-Dorg.apache.lucene.store.defaultReadAdvice=normal`. This may be useful on systems
with lots of RAM as this increases read-ahead. (Adrien Grand, Uwe Schindler)
Changes in Backwards Compatibility Policy
-----------------------------------------

14
lucene/core/src/java/org/apache/lucene/store/IOContext.java
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@ -18,6 +18,7 @@ package org.apache.lucene.store;
import java.util.Arrays;
import java.util.Objects;
import org.apache.lucene.util.Constants;
/**
* IOContext holds additional details on the merge/search context. An IOContext object can never be
@ -48,15 +49,15 @@ public record IOContext(
/**
* A default context for normal reads/writes. Use {@link #withReadAdvice(ReadAdvice)} to specify
* another {@link ReadAdvice}.
*
* <p>It will use {@link ReadAdvice#RANDOM} by default, unless set by system property {@code
* org.apache.lucene.store.defaultReadAdvice}.
*/
public static final IOContext DEFAULT = new IOContext(ReadAdvice.RANDOM);
public static final IOContext DEFAULT = new IOContext(Constants.DEFAULT_READADVICE);
/** A default context for reads with {@link ReadAdvice#SEQUENTIAL}. */
public static final IOContext READONCE = new IOContext(ReadAdvice.SEQUENTIAL);
private static final IOContext[] DEFAULT_READADVICE_CACHE =
Arrays.stream(ReadAdvice.values()).map(IOContext::new).toArray(IOContext[]::new);
@SuppressWarnings("incomplete-switch")
public IOContext {
Objects.requireNonNull(context, "context must not be null");
@ -90,6 +91,9 @@ public record IOContext(
this(Context.MERGE, mergeInfo, null, ReadAdvice.SEQUENTIAL);
}
private static final IOContext[] READADVICE_TO_IOCONTEXT =
Arrays.stream(ReadAdvice.values()).map(IOContext::new).toArray(IOContext[]::new);
/**
* Return an updated {@link IOContext} that has the provided {@link ReadAdvice} if the {@link
* Context} is a {@link Context#DEFAULT} context, otherwise return this existing instance. This
@ -99,7 +103,7 @@ public record IOContext(
*/
public IOContext withReadAdvice(ReadAdvice advice) {
if (context == Context.DEFAULT) {
return DEFAULT_READADVICE_CACHE[advice.ordinal()];
return READADVICE_TO_IOCONTEXT[advice.ordinal()];
} else {
return this;
}

13
lucene/core/src/java/org/apache/lucene/util/Constants.java
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@ -18,7 +18,10 @@ package org.apache.lucene.util;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Locale;
import java.util.Optional;
import java.util.logging.Logger;
import org.apache.lucene.store.ReadAdvice;
/** Some useful constants. */
public final class Constants {
@ -152,6 +155,16 @@ public final class Constants {
return false;
}
/**
* The default {@link ReadAdvice} used for opening index files. It will be {@link
* ReadAdvice#RANDOM} by default, unless set by system property {@code
* org.apache.lucene.store.defaultReadAdvice}.
*/
public static final ReadAdvice DEFAULT_READADVICE =
Optional.ofNullable(getSysProp("org.apache.lucene.store.defaultReadAdvice"))
.map(a -> ReadAdvice.valueOf(a.toUpperCase(Locale.ROOT)))
.orElse(ReadAdvice.RANDOM);
private static String getSysProp(String property) {
try {
return doPrivileged(() -> System.getProperty(property));