t = db.index_check2;
t.drop();

// Include helpers for analyzing explain output.
load("jstests/libs/analyze_plan.js");

for ( var i=0; i<1000; i++ ){
    var a = [];
    for ( var j=1; j<5; j++ ){
        a.push( "tag" + ( i * j % 50 ));
    }
    t.save( { num : i , tags : a } );
}

q1 = { tags : "tag6" };
q2 = { tags : "tag12" };
q3 = { tags : { $all : [ "tag6" , "tag12" ] } }

assert.eq( 120 , t.find( q1 ).itcount() , "q1 a");
assert.eq( 120 , t.find( q2 ).itcount() , "q2 a" );
assert.eq( 60 , t.find( q3 ).itcount() , "q3 a");

t.ensureIndex( { tags : 1 } );

assert.eq( 120 , t.find( q1 ).itcount() , "q1 a");
assert.eq( 120 , t.find( q2 ).itcount() , "q2 a" );
assert.eq( 60 , t.find( q3 ).itcount() , "q3 a");

// We expect these queries to use index scans over { tags: 1 }.
assert( isIxscan(t.find(q1).explain().queryPlanner.winningPlan) , "e1" );
assert( isIxscan(t.find(q2).explain().queryPlanner.winningPlan) , "e2" );
assert( isIxscan(t.find(q3).explain().queryPlanner.winningPlan) , "e3" );

scanned1 = t.find(q1).explain("executionStats").executionStats.totalKeysExamined;
scanned2 = t.find(q2).explain("executionStats").executionStats.totalKeysExamined;
scanned3 = t.find(q3).explain("executionStats").executionStats.totalKeysExamined;

//print( "scanned1: " + scanned1 + " scanned2: " + scanned2 + " scanned3: " + scanned3 );

// $all should just iterate either of the words
assert( scanned3 <= Math.max( scanned1 , scanned2 ) , "$all makes query optimizer not work well" );