SERVER-9856 check in-progress indexes for duplicates in prepareToBuildIndex()

4 files changed, 30 insertions, 8 deletions

diff --git a/jstests/slowNightly/dup_bgindex.js b/jstests/slowNightly/dup_bgindex.js
new file mode 100644
index 00000000000..fbfb8a8a322
--- /dev/null
+++ b/jstests/slowNightly/dup_bgindex.js
@@ -0,0 +1,16 @@
+// Try to create two identical indexes, via background. Shouldn't be allowed by the server.
+// This test runs fairly quickly but cannot be in /jstests/. So it lives in slowNightly for now.
+var t = db.duplIndexTest;
+t.drop();
+for (var i=0; i<10000; i++) {
+  t.insert( { name : "foo" , z : { a : 17 , b : 4}, i: i } );
+}
+var cmd = "db.duplIndexTest.ensureIndex( { i : 1 }, {background:true} );"
+var join1 = startParallelShell(cmd);
+var join2 = startParallelShell(cmd);
+t.ensureIndex( { i : 1 }, {background:true} );
+assert.eq(1, t.find({i:1}).count(), "Should find only one doc");
+t.dropIndex({ i : 1 });
+assert.eq(1, t.find({i:1}).count(), "Should find only one doc");
+join1();
+join2();
diff --git a/src/mongo/db/index.cpp b/src/mongo/db/index.cpp
index 377679806a4..f7346978313 100644
--- a/src/mongo/db/index.cpp
+++ b/src/mongo/db/index.cpp
@@ -369,11 +369,14 @@ namespace mongo {
             verify( sourceCollection );
         }
 
-        if ( sourceCollection->findIndexByName(name) >= 0 ) {
+        // Check both existing and in-progress indexes (2nd param = true)
+        if ( sourceCollection->findIndexByName(name, true) >= 0 ) {
             // index already exists.
             return false;
         }
-        if( sourceCollection->findIndexByKeyPattern(key) >= 0 ) {
+
+        // Check both existing and in-progress indexes (2nd param = true)
+        if( sourceCollection->findIndexByKeyPattern(key, true) >= 0 ) {
             LOG(2) << "index already exists with diff name " << name << ' ' << key.toString() << endl;
             return false;
         }
diff --git a/src/mongo/db/namespace_details-inl.h b/src/mongo/db/namespace_details-inl.h
index 0e64b961ba8..9e8ccbb37e6 100644
--- a/src/mongo/db/namespace_details-inl.h
+++ b/src/mongo/db/namespace_details-inl.h
@@ -56,8 +56,9 @@ namespace mongo {
         return -1;
     }
 
-    inline int NamespaceDetails::findIndexByKeyPattern(const BSONObj& keyPattern) {
-        IndexIterator i = ii();
+    inline int NamespaceDetails::findIndexByKeyPattern(const BSONObj& keyPattern,
+                                                       bool includeBackgroundInProgress) {
+        IndexIterator i = ii(includeBackgroundInProgress);
         while( i.more() ) {
             if( i.next().keyPattern() == keyPattern )
                 return i.pos()-1;
@@ -83,8 +84,9 @@ namespace mongo {
     }
 
     // @return offset in indexes[]
-    inline int NamespaceDetails::findIndexByName(const char *name) {
-        IndexIterator i = ii();
+    inline int NamespaceDetails::findIndexByName(const char *name,
+                                                 bool includeBackgroundInProgress) {
+        IndexIterator i = ii(includeBackgroundInProgress);
         while( i.more() ) {
             if ( strcmp(i.next().info.obj().getStringField("name"),name) == 0 )
                 return i.pos()-1;
diff --git a/src/mongo/db/namespace_details.h b/src/mongo/db/namespace_details.h
index 28416f4abf0..0e7e324da67 100644
--- a/src/mongo/db/namespace_details.h
+++ b/src/mongo/db/namespace_details.h
@@ -291,10 +291,11 @@ namespace mongo {
         }
 
         // @return offset in indexes[]
-        int findIndexByName(const char *name);
+        int findIndexByName(const char *name, bool includeBackgroundInProgress = false);
 
         // @return offset in indexes[]
-        int findIndexByKeyPattern(const BSONObj& keyPattern);
+        int findIndexByKeyPattern(const BSONObj& keyPattern, 
+                                  bool includeBackgroundInProgress = false);
 
         void findIndexByType( const string& name , vector<int>& matches ) {
             IndexIterator i = ii();