ExportReviewNotes: Default to 2 threads

Not all systems have enough database connections in the connection
pool to support 2 threads per CPU. Exporting lots of changes doesn't
take that long, so 2 threads is acceptable.

Change-Id: I69bbade7f67023689ca54665833bc764d2d5503d
Signed-off-by: Shawn O. Pearce <sop@google.com>
diff --git a/Documentation/pgm-ExportReviewNotes.txt b/Documentation/pgm-ExportReviewNotes.txt
index b43989f..602c245 100644
--- a/Documentation/pgm-ExportReviewNotes.txt
+++ b/Documentation/pgm-ExportReviewNotes.txt
@@ -29,8 +29,7 @@
 	configuration data, supporting libaries and log files.
 
 \--threads::
-	Number of threads to perform the scan work with.  Defaults to
-	twice the number of CPUs available.
+	Number of threads to perform the scan work with.  Default: 2.
 
 CONTEXT
 -------
diff --git a/gerrit-pgm/src/main/java/com/google/gerrit/pgm/ExportReviewNotes.java b/gerrit-pgm/src/main/java/com/google/gerrit/pgm/ExportReviewNotes.java
index b8e4160..71512f2 100644
--- a/gerrit-pgm/src/main/java/com/google/gerrit/pgm/ExportReviewNotes.java
+++ b/gerrit-pgm/src/main/java/com/google/gerrit/pgm/ExportReviewNotes.java
@@ -63,7 +63,7 @@
 /** Export review notes for all submitted changes in all projects. */
 public class ExportReviewNotes extends SiteProgram {
   @Option(name = "--threads", usage = "Number of concurrent threads to run")
-  private int threads = 2 * Runtime.getRuntime().availableProcessors();
+  private int threads = 2;
 
   private final LifecycleManager manager = new LifecycleManager();
   private final TextProgressMonitor textMonitor = new TextProgressMonitor();