From 15b81c91f776397b7b564cf3179be5226bd2ad55 Mon Sep 17 00:00:00 2001
From: mikemccand <mail@mikemccandless.com>
Date: Mon, 7 Jul 2014 11:34:46 -0400
Subject: [PATCH] Core: remove per-ID locking when ID was auto-generated

When we know the ID for the document we are about to index was
auto-generated, we don't need to acquire/release the per-ID lock,
which might provide small speedups during highly concurrent indexing.

Closes #6584
---
 .../index/engine/internal/InternalEngine.java | 82 ++++++++++---------
 1 file changed, 43 insertions(+), 39 deletions(-)

diff --git a/src/main/java/org/elasticsearch/index/engine/internal/InternalEngine.java b/src/main/java/org/elasticsearch/index/engine/internal/InternalEngine.java
index c8f0cfd9d87..2c8ee66d30f 100644
--- a/src/main/java/org/elasticsearch/index/engine/internal/InternalEngine.java
+++ b/src/main/java/org/elasticsearch/index/engine/internal/InternalEngine.java
@@ -402,13 +402,13 @@ public class InternalEngine extends AbstractIndexShardComponent implements Engin
     }
 
     private void innerCreate(Create create, IndexWriter writer) throws IOException {
-        synchronized (dirtyLock(create.uid())) {
-            final long currentVersion;
-            final VersionValue versionValue;
-            if (optimizeAutoGenerateId && create.autoGeneratedId() && !create.canHaveDuplicates()) {
-                currentVersion = Versions.NOT_FOUND;
-                versionValue = null;
-            } else {
+        if (optimizeAutoGenerateId && create.autoGeneratedId() && !create.canHaveDuplicates()) {
+            // We don't need to lock because this ID cannot be concurrently updated:
+            innerCreateNoLock(create, writer, Versions.NOT_FOUND, null);
+        } else {
+            synchronized (dirtyLock(create.uid())) {
+                final long currentVersion;
+                final VersionValue versionValue;
                 versionValue = versionMap.getUnderLock(create.uid().bytes());
                 if (versionValue == null) {
                     currentVersion = loadCurrentVersionFromIndex(create.uid());
@@ -419,51 +419,55 @@ public class InternalEngine extends AbstractIndexShardComponent implements Engin
                         currentVersion = versionValue.version();
                     }
                 }
+                innerCreateNoLock(create, writer, currentVersion, versionValue);
             }
+        }
+    }
 
-            // same logic as index
-            long updatedVersion;
-            long expectedVersion = create.version();
-            if (create.versionType().isVersionConflictForWrites(currentVersion, expectedVersion)) {
-                if (create.origin() == Operation.Origin.RECOVERY) {
-                    return;
-                } else {
-                    throw new VersionConflictEngineException(shardId, create.type(), create.id(), currentVersion, expectedVersion);
-                }
+    private void innerCreateNoLock(Create create, IndexWriter writer, long currentVersion, VersionValue versionValue) throws IOException {
+
+        // same logic as index
+        long updatedVersion;
+        long expectedVersion = create.version();
+        if (create.versionType().isVersionConflictForWrites(currentVersion, expectedVersion)) {
+            if (create.origin() == Operation.Origin.RECOVERY) {
+                return;
+            } else {
+                throw new VersionConflictEngineException(shardId, create.type(), create.id(), currentVersion, expectedVersion);
             }
-            updatedVersion = create.versionType().updateVersion(currentVersion, expectedVersion);
+        }
+        updatedVersion = create.versionType().updateVersion(currentVersion, expectedVersion);
 
-            // if the doc does not exist or it exists but is not deleted
-            if (versionValue != null) {
-                if (!versionValue.delete()) {
-                    if (create.origin() == Operation.Origin.RECOVERY) {
-                        return;
-                    } else {
-                        throw new DocumentAlreadyExistsException(shardId, create.type(), create.id());
-                    }
-                }
-            } else if (currentVersion != Versions.NOT_FOUND) {
-                // its not deleted, its already there
+        // if the doc does not exist or it exists but is not deleted
+        if (versionValue != null) {
+            if (!versionValue.delete()) {
                 if (create.origin() == Operation.Origin.RECOVERY) {
                     return;
                 } else {
                     throw new DocumentAlreadyExistsException(shardId, create.type(), create.id());
                 }
             }
-
-            create.updateVersion(updatedVersion);
-
-            if (create.docs().size() > 1) {
-                writer.addDocuments(create.docs(), create.analyzer());
+        } else if (currentVersion != Versions.NOT_FOUND) {
+            // its not deleted, its already there
+            if (create.origin() == Operation.Origin.RECOVERY) {
+                return;
             } else {
-                writer.addDocument(create.docs().get(0), create.analyzer());
+                throw new DocumentAlreadyExistsException(shardId, create.type(), create.id());
             }
-            Translog.Location translogLocation = translog.add(new Translog.Create(create));
-
-            versionMap.putUnderLock(create.uid().bytes(), new VersionValue(updatedVersion, translogLocation));
-
-            indexingService.postCreateUnderLock(create);
         }
+
+        create.updateVersion(updatedVersion);
+
+        if (create.docs().size() > 1) {
+            writer.addDocuments(create.docs(), create.analyzer());
+        } else {
+            writer.addDocument(create.docs().get(0), create.analyzer());
+        }
+        Translog.Location translogLocation = translog.add(new Translog.Create(create));
+
+        versionMap.putUnderLock(create.uid().bytes(), new VersionValue(updatedVersion, translogLocation));
+
+        indexingService.postCreateUnderLock(create);
     }
 
     @Override