backport of SERVER-4612 - fix chhunk boundary checking on idhack queries

db/ops/query.cpp

@@ -916,6 +916,19 @@ namespace mongo {
             Client& c = cc();
             bool found = Helpers::findById( c, ns , query , resObject , &nsFound , &indexFound );
             if ( nsFound == false || indexFound == true ) {
+
+                if ( shardingState.needShardChunkManager( ns ) ) {
+                    ShardChunkManagerPtr m = shardingState.getShardChunkManager( ns );
+                    if ( m && ! m->belongsToMe( resObject ) ) {
+                        // I have something this _id
+                        // but it doesn't belong to me
+                        // so return nothing
+                        resObject = BSONObj();
+                        found = false;
+                    }
+                }
+
+
                 BufBuilder bb(sizeof(QueryResult)+resObject.objsize()+32);
                 bb.skip(sizeof(QueryResult));
 

jstests/sharding/shard3.js

@@ -61,14 +61,20 @@ function doCounts( name , total , onlyItCounts ){
 }
 
 var total = doCounts( "before wrong save" )
-secondary.save( { num : -3 } );
+secondary.save( { _id : 111 , num : -3 } );
 printjson( secondary.getDB().getLastError() )
 doCounts( "after wrong save" , total , true )
 e = a.find().explain();
 assert.eq( 3 , e.n , "ex1" )
 assert.eq( 4 , e.nscanned , "ex2" )
 assert.eq( 1 , e.nChunkSkips , "ex3" )
 
+
+// SERVER-4612 
+// make sure idhack obeys chunks
+x = a.findOne( { _id : 111 } )
+assert( ! x , "idhack didn't obey chunk boundaries " + tojson(x) );
+
 // --- move all to 1 ---
 print( "MOVE ALL TO 1" );