From a4a53664446b5f6a466b386773d89ff992093617 Mon Sep 17 00:00:00 2001
From: Gustaf Lundh <gustaf.lundh@sonymobile.com>
Date: Tue, 19 Nov 2013 17:21:28 +0100
Subject: [PATCH] Performance Fix: Minimize number of advertisedHaves

While we set up hooks in ReceiveCommits to minimize the number of
advertised refs (for instance filtering out refs/changes and
refs/cache-automerge refs), their objectIds will still be added to
BaseReceivePack.advertisedHaves (JGit), leading to an unnecessarily
complex commit graph for JGit to traverse when checking for commit
connectivity in BaseReceivePack.checkConnectivity().

By filtering the refs before the objectIds are added to advertisedHaves,
lots of time can be saved when pushing to complex Gits.

Push times for one of our Gits (warm caches):

Before fix:
real	0m42.926s

After fix:
real	0m6.325s

This Git has around 90k change/ps refs.

Change-Id: I2f0a0830bd733f908f0aeaf1eaf0412dae428a16
---
 .../google/gerrit/server/git/ReceiveCommits.java | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/git/ReceiveCommits.java b/gerrit-server/src/main/java/com/google/gerrit/server/git/ReceiveCommits.java
index bcc30144fc..897b53a81c 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/git/ReceiveCommits.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/git/ReceiveCommits.java
@@ -18,7 +18,6 @@ import static com.google.gerrit.reviewdb.client.Change.INITIAL_PATCH_SET_ID;
 import static com.google.gerrit.server.git.MultiProgressMonitor.UNKNOWN;
 import static com.google.gerrit.server.mail.MailUtil.getRecipientsFromApprovals;
 import static com.google.gerrit.server.mail.MailUtil.getRecipientsFromFooters;
-
 import static org.eclipse.jgit.lib.Constants.R_HEADS;
 import static org.eclipse.jgit.transport.ReceiveCommand.Result.NOT_ATTEMPTED;
 import static org.eclipse.jgit.transport.ReceiveCommand.Result.OK;
@@ -114,6 +113,7 @@ import org.eclipse.jgit.transport.AdvertiseRefsHook;
 import org.eclipse.jgit.transport.AdvertiseRefsHookChain;
 import org.eclipse.jgit.transport.BaseReceivePack;
 import org.eclipse.jgit.transport.ReceiveCommand;
+import org.eclipse.jgit.transport.RefFilter;
 import org.eclipse.jgit.transport.ReceiveCommand.Result;
 import org.eclipse.jgit.transport.ReceivePack;
 import org.eclipse.jgit.transport.UploadPack;
@@ -363,6 +363,20 @@ public class ReceiveCommits {
     rp.setAllowDeletes(true);
     rp.setAllowNonFastForwards(true);
     rp.setCheckReceivedObjects(true);
+    rp.setRefFilter(new RefFilter() {
+      @Override
+      public Map<String, Ref> filter(Map<String, Ref> refs) {
+        Map<String, Ref> filteredRefs = Maps.newHashMapWithExpectedSize(refs.size());
+        for (Map.Entry<String, Ref> e : refs.entrySet()) {
+          String name = e.getKey();
+          if (!name.startsWith("refs/changes/")
+              && !name.startsWith(GitRepositoryManager.REFS_CACHE_AUTOMERGE)) {
+            filteredRefs.put(name, e.getValue());
+          }
+        }
+        return filteredRefs;
+      }
+    });
 
     if (!projectControl.allRefsAreVisible()) {
       rp.setCheckReferencedObjectsAreReachable(config.checkReferencedObjectsAreReachable);