t = db.slice1; t.drop(); t.insert({_id:1, a:[0,1,2,3,4,5,-5,-4,-3,-2,-1], b:1, c:1}); // first three out = t.findOne({}, {a:{$slice:3}}); assert.eq(out.a , [0,1,2], '1'); // last three out = t.findOne({}, {a:{$slice:-3}}); assert.eq(out.a , [-3, -2, -1], '2'); // skip 2, limit 3 out = t.findOne({}, {a:{$slice:[2, 3]}}); assert.eq(out.a , [2,3,4], '3'); // skip to fifth from last, limit 4 out = t.findOne({}, {a:{$slice:[-5, 4]}}); assert.eq(out.a , [-5, -4, -3, -2], '4'); // skip to fifth from last, limit 10 out = t.findOne({}, {a:{$slice:[-5, 10]}}); assert.eq(out.a , [-5, -4, -3, -2, -1], '5'); // interaction with other fields out = t.findOne({}, {a:{$slice:3}}); assert.eq(out.a , [0,1,2], 'A 1'); assert.eq(out.b , 1, 'A 2'); assert.eq(out.c , 1, 'A 3'); out = t.findOne({}, {a:{$slice:3}, b:true}); assert.eq(out.a , [0,1,2], 'B 1'); assert.eq(out.b , 1, 'B 2'); assert.eq(out.c , undefined); out = t.findOne({}, {a:{$slice:3}, b:false}); assert.eq(out.a , [0,1,2]); assert.eq(out.b , undefined); assert.eq(out.c , 1); t.drop() t.insert({comments: [{id:0, text:'a'},{id:1, text:'b'},{id:2, text:'c'},{id:3, text:'d'}], title:'foo'}) out = t.findOne({}, {comments:{$slice:2}, 'comments.id':true}); assert.eq(out.comments , [{id:0}, {id:1}]); assert.eq(out.title , undefined); out = t.findOne({}, {comments:{$slice:2}, 'comments.id':false}); assert.eq(out.comments , [{text: 'a'}, {text: 'b'}]); assert.eq(out.title , 'foo'); //nested arrays t.drop(); t.insert({_id:1, a:[[1,1,1], [2,2,2], [3,3,3]], b:1, c:1}); out = t.findOne({}, {a:{$slice:1}}); assert.eq(out.a , [[1,1,1]], 'n 1'); out = t.findOne({}, {a:{$slice:-1}}); assert.eq(out.a , [[3,3,3]], 'n 2'); out = t.findOne({}, {a:{$slice:[0,2]}}); assert.eq(out.a , [[1,1,1],[2,2,2]], 'n 2');