commit 569f8dca84dcfd469244a0983ba07d6ee381d814
author Shawn Pearce <sop@google.com> Fri Sep 13 15:12:20 2013 -0700
committer Shawn Pearce <sop@google.com> Fri Sep 13 15:12:20 2013 -0700
tree e35d2ac135b4a00adc3b298bfe06616fd51b61d1
parent 44a6a5a2090096ac38bc1966151c0c564d133a65

Run parallel queries asynchronously

Dave Borowitz suggested changing the calling convention for the
rewriter to delay starting the query until read() is invoked on
ChangeDataSource. This allows creating index predicates that are
discarded and replaced by other rewrite steps.

Change-Id: I4f9e0f8407340b5b489adad971990e710b8121f0

gerrit-server/src/main/java/com/google/gerrit/server/query/change/QueryProcessor.java

diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/QueryProcessor.java b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/QueryProcessor.java
index 72c7138..0bf13b4 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/QueryProcessor.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/QueryProcessor.java
@@ -33,6 +33,7 @@
 import com.google.gerrit.server.query.QueryParseException;
 import com.google.gson.Gson;
 import com.google.gwtorm.server.OrmException;
+import com.google.gwtorm.server.ResultSet;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
 
@@ -229,7 +230,7 @@
     final Predicate<ChangeData> visibleToMe = queryBuilder.is_visible();
     int cnt = queries.size();
 
-    // Begin all queries, possibly asynchronously.
+    // Parse and rewrite all queries.
     List<Integer> limits = Lists.newArrayListWithCapacity(cnt);
     List<ChangeDataSource> sources = Lists.newArrayListWithCapacity(cnt);
     for (int i = 0; i < cnt; i++) {
@@ -251,9 +252,16 @@
       sources.add(a);
     }
 
+    // Run each query asynchronously, if supported.
+    List<ResultSet<ChangeData>> matches = Lists.newArrayListWithCapacity(cnt);
+    for (ChangeDataSource s : sources) {
+      matches.add(s.read());
+    }
+    sources = null;
+
     List<List<ChangeData>> out = Lists.newArrayListWithCapacity(cnt);
     for (int i = 0; i < cnt; i++) {
-      List<ChangeData> results = Lists.newArrayList(sources.get(i).read());
+      List<ChangeData> results = Lists.newArrayList(matches.get(i).toList());
       Collections.sort(results, sortkeyAfter != null ? cmpAfter : cmpBefore);
       if (results.size() > maxLimit) {
         moreResults = true;