Speed up ContentProvider.query() in simple case by ~30%

When query() uses bulkQuery() and we know we're going to need some
metadata right afterwards (number of rows and column index of _id, if
present), just asked for it in the initial binder transaction instead
of immediately fetching it again.

Also, this defers loading column names until the client asks for them.

This gets down the simpler (and very common) use cases of
ContentProvider.query() down to 3 binder calls:

   QUERY_TRANSACTION to android.content.ContentProvider$Transport
   GET_CURSOR_WINDOW_TRANSACTION to android.database.CursorToBulkCursorAdaptor
   CLOSE_TRANSACTION to android.database.CursorToBulkCursorAdaptor

More can still be done, but this is a good bite-sized first piece.

Change-Id: I7ad45949f53e0097ff18c2478d659f0f36929693

1 files changed, 54 insertions, 9 deletions

diff --git a/core/java/android/content/ContentProviderNative.java b/core/java/android/content/ContentProviderNative.java
index de52e65f52f7..fdb3d20c9f99 100644
--- a/core/java/android/content/ContentProviderNative.java
+++ b/core/java/android/content/ContentProviderNative.java
@@ -73,7 +73,10 @@ abstract public class ContentProviderNative extends Binder implements IContentPr
                 case QUERY_TRANSACTION:
                 {
                     data.enforceInterface(IContentProvider.descriptor);
+
                     Uri url = Uri.CREATOR.createFromParcel(data);
+
+                    // String[] projection
                     int num = data.readInt();
                     String[] projection = null;
                     if (num > 0) {
@@ -82,6 +85,8 @@ abstract public class ContentProviderNative extends Binder implements IContentPr
                             projection[i] = data.readString();
                         }
                     }
+
+                    // String selection, String[] selectionArgs...
                     String selection = data.readString();
                     num = data.readInt();
                     String[] selectionArgs = null;
@@ -91,19 +96,33 @@ abstract public class ContentProviderNative extends Binder implements IContentPr
                             selectionArgs[i] = data.readString();
                         }
                     }
+
                     String sortOrder = data.readString();
                     IContentObserver observer = IContentObserver.Stub.
                         asInterface(data.readStrongBinder());
                     CursorWindow window = CursorWindow.CREATOR.createFromParcel(data);
 
+                    // Flag for whether caller wants the number of
+                    // rows in the cursor and the position of the
+                    // "_id" column index (or -1 if non-existent)
+                    // Only to be returned if binder != null.
+                    boolean wantsCursorMetadata = data.readInt() != 0;
+
                     IBulkCursor bulkCursor = bulkQuery(url, projection, selection,
                             selectionArgs, sortOrder, observer, window);
                     reply.writeNoException();
                     if (bulkCursor != null) {
                         reply.writeStrongBinder(bulkCursor.asBinder());
+
+                        if (wantsCursorMetadata) {
+                            reply.writeInt(bulkCursor.count());
+                            reply.writeInt(BulkCursorToCursorAdaptor.findRowIdColumnIndex(
+                                bulkCursor.getColumnNames()));
+                        }
                     } else {
                         reply.writeStrongBinder(null);
                     }
+
                     return true;
                 }
 
@@ -266,9 +285,12 @@ final class ContentProviderProxy implements IContentProvider
         return mRemote;
     }
 
-    public IBulkCursor bulkQuery(Uri url, String[] projection,
-            String selection, String[] selectionArgs, String sortOrder, IContentObserver observer,
-            CursorWindow window) throws RemoteException {
+    // Like bulkQuery() but sets up provided 'adaptor' if not null.
+    private IBulkCursor bulkQueryInternal(
+        Uri url, String[] projection,
+        String selection, String[] selectionArgs, String sortOrder,
+        IContentObserver observer, CursorWindow window,
+        BulkCursorToCursorAdaptor adaptor) throws RemoteException {
         Parcel data = Parcel.obtain();
         Parcel reply = Parcel.obtain();
 
@@ -297,6 +319,12 @@ final class ContentProviderProxy implements IContentProvider
         data.writeStrongBinder(observer.asBinder());
         window.writeToParcel(data, 0);
 
+        // Flag for whether or not we want the number of rows in the
+        // cursor and the position of the "_id" column index (or -1 if
+        // non-existent).  Only to be returned if binder != null.
+        final boolean wantsCursorMetadata = (adaptor != null);
+        data.writeInt(wantsCursorMetadata ? 1 : 0);
+
         mRemote.transact(IContentProvider.QUERY_TRANSACTION, data, reply, 0);
 
         DatabaseUtils.readExceptionFromParcel(reply);
@@ -305,26 +333,43 @@ final class ContentProviderProxy implements IContentProvider
         IBinder bulkCursorBinder = reply.readStrongBinder();
         if (bulkCursorBinder != null) {
             bulkCursor = BulkCursorNative.asInterface(bulkCursorBinder);
+
+            if (wantsCursorMetadata) {
+                int rowCount = reply.readInt();
+                int idColumnPosition = reply.readInt();
+                if (bulkCursor != null) {
+                    adaptor.set(bulkCursor, rowCount, idColumnPosition);
+                }
+            }
         }
-        
+
         data.recycle();
         reply.recycle();
-        
+
         return bulkCursor;
     }
 
+    public IBulkCursor bulkQuery(Uri url, String[] projection,
+            String selection, String[] selectionArgs, String sortOrder, IContentObserver observer,
+            CursorWindow window) throws RemoteException {
+        return bulkQueryInternal(
+            url, projection, selection, selectionArgs, sortOrder,
+            observer, window,
+            null /* BulkCursorToCursorAdaptor */);
+    }
+
     public Cursor query(Uri url, String[] projection, String selection,
             String[] selectionArgs, String sortOrder) throws RemoteException {
         //TODO make a pool of windows so we can reuse memory dealers
         CursorWindow window = new CursorWindow(false /* window will be used remotely */);
         BulkCursorToCursorAdaptor adaptor = new BulkCursorToCursorAdaptor();
-        IBulkCursor bulkCursor = bulkQuery(url, projection, selection, selectionArgs, sortOrder,
-                adaptor.getObserver(), window);
-
+        IBulkCursor bulkCursor = bulkQueryInternal(
+            url, projection, selection, selectionArgs, sortOrder,
+            adaptor.getObserver(), window,
+            adaptor);
         if (bulkCursor == null) {
             return null;
         }
-        adaptor.set(bulkCursor);
         return adaptor;
     }