MongoDB :: Order Search result depend on search condition - mongodb

Question

I have a data
[{ "name":"BS",
"keyword":"key1",
"city":"xyz"
},
{ "name":"AGS",
"keyword":"Key2",
"city":"xyz1"
},
{ "name":"QQQ",
"keyword":"key3",
"city":"xyz"
},
{ "name":"BS",
"keyword":"Keyword",
"city":"city"
}]
and i need to search records which have name= "BS" OR keyword="key2" with the help of query
db.collection.find({"$OR" : [{"name":"BS"}, {"keyword":"Key2"}]});
These records i need in the sequence
[{ "name":"BS",
"keyword":"key1",
"city":"xyz"
},
{ "name":"BS",
"keyword":"Keyword",
"city":"city"
},
{ "name":"AGS",
"keyword":"Key2",
"city":"xyz1"
}]
but i am getting in following sequences:
[{ "name":"BS",
"keyword":"key1",
"city":"xyz"
},
{ "name":"AGS",
"keyword":"Key2",
"city":"xyz1"
},
{ "name":"BS",
"keyword":"Keyword",
"city":"city"
}]
Please provide some suggestion i am stuck with this problem since 2 days.
Thanks

Answer 1

The order of results returned by MongoDB is not guaranteed unless you explicitly sort your data using the sort function. For smaller datasets you maybe "lucky" in the sense that the results are always returned in the same order, however, for bigger datasets and in particular when you have sharded Mongo clusters this is very unlikely. As proposed by Yathish you need to explicitly order your results using the sort function. Based on the suggested output, it seems you want to sort by name in descending order so I have set the sorting flag to -1 for the field name.
db.collection.find({"$or" : [{"name":"BS"}, {"keyword":"Key2"}]}).sort({"name" : -1});
If you need a more complex sorting algorithm as specified in your comment, you can convert your results to a Javascript array and create a custom sort function. This sort function will first list documents with a name equal to "BS" and then documents containing the keyword "Key2"
db.data.find({
"$or": [{
"name": "BS"
}, {
"keyword": "Key2"
}]
}).toArray().sort(function(doc1, doc2) {
if (doc1.name == "BS" && doc2.keyword == "Key2") {
return -1
} else if (doc2.name == "BS" && doc1.keyword == "Key2") {
return 1
} else {
return doc1.name < doc2.name
}
});