Select index if query contains condition for first index fieldr0.2.1

2 files changed, 7 insertions, 8 deletions

diff --git a/db/query.cpp b/db/query.cpp
index 5195dea984a..0bb52368554 100644
--- a/db/query.cpp
+++ b/db/query.cpp
@@ -155,15 +155,8 @@ namespace mongo {
         for (int i = 0; i < d->nIndexes; i++ ) {
             BSONObj idxInfo = d->indexes[i].info.obj(); // { name:, ns:, key: }
             BSONObj idxKey = idxInfo.getObjectField("key");
-            set<string> keyFields;
-            idxKey.getFieldNames(keyFields);
 
-            bool subset = true;
-            for( set<string>::iterator j = queryFields.begin(); subset && j != queryFields.end(); ++j )
-                if ( keyFields.count( *j ) == 0 )
-                    subset = false;
-            
-            if ( subset ) {
+            if ( queryFields.count( idxKey.firstElement().fieldName() ) > 0 ) {
                 BSONObj q = query.extractFieldsUnDotted(idxKey);
                 assert(q.objsize() != 0); // guard against a seg fault if details is 0
                                                                                                                
diff --git a/jstests/index7.js b/jstests/index7.js
index bfbe9c8e07f..b5a308e79db 100644
--- a/jstests/index7.js
+++ b/jstests/index7.js
@@ -50,6 +50,12 @@ noIndex( f.find().sort( { b: 1, a: 1 } ) );
 noIndex( f.find() );
 noIndex( f.find( { c: 1 } ) );
 index( f.find( { a: 1 } ) );
+assert.eq( 1, f.find( { a: 1 } ).explain().startKey.a );
+assert.eq( 1, f.find( { a: 1 } ).explain().endKey.a );
+index( f.find( { a: 1, c: 1 } ) );
+assert.eq( 1, f.find( { a: 1, c: 1 } ).explain().startKey.a );
+assert.eq( 1, f.find( { a: 1, c: 1 } ).explain().endKey.a );
+noIndex( f.find( { b: 1 } ) );
 index( f.find( { a: 1, b: 1 } ) );
 index( f.find( { b: 1, a: 1 } ) );