mongodb query multiple pairs using $in - sql

Question

I have a collection names with data (_id is omitted):
{first:"John", last:"Smith"},
{first:"Alice", last:"Johnson"},
{first:"Bob", last:"Williams"},
...
and {first, last} is a unique index.
I want to find a lot of names in names like:
db.names.find({$or: [{first:"Alice", last:"Brown"}, {first:"Bob", last:"White"}, ...]}
Can I use $in instead of $or to simplify this query?
===
I know in MySQL this following query:
SELECT * FROM names WHERE (first = 'Alice' AND last = 'Brown') OR (first = 'Bob' AND last = 'White') OR ...
can be simplified as:
SELECT * FROM names WHERE (first, last) IN (('Alice', 'Brown'), ('Bob','White') OR ...)
But I am unable to find the equivalent query syntax in MongoDB.

Answer 1

The following query can get us the expected output:
db.names.find({
$expr:{
$in:[
{
"first":"$first",
"last":"$last"
},
[
{
"first" : "Alice",
"last" : "Johnson"
},
{
"first" : "Bob",
"last" : "Williams"
}
]
]
}
}).pretty()
Data set:
{
"_id" : ObjectId("5d81c3b7a832f81a9e02337b"),
"first" : "John",
"last" : "Smith"
}
{
"_id" : ObjectId("5d81c3b7a832f81a9e02337c"),
"first" : "Alice",
"last" : "Johnson"
}
{
"_id" : ObjectId("5d81c3b7a832f81a9e02337d"),
"first" : "Bob",
"last" : "Williams"
}
Output:
{
"_id" : ObjectId("5d81c3b7a832f81a9e02337c"),
"first" : "Alice",
"last" : "Johnson"
}
{
"_id" : ObjectId("5d81c3b7a832f81a9e02337d"),
"first" : "Bob",
"last" : "Williams"
}
Query Analysis: This query won't use the unique index you have created and I would recommend to go with the $or query.
Following are the winning plans:
$or query:
{
"stage" : "COLLSCAN",
"filter" : {
"$expr" : {
"$in" : [
{
"first" : "$first",
"last" : "$last"
},
{
"$const" : [
{
"first" : "Alice",
"last" : "Johnson"
},
{
"first" : "Bob",
"last" : "Williams"
}
]
}
]
}
},
"direction" : "forward"
}
$in query:
{
"stage" : "SUBPLAN",
"inputStage" : {
"stage" : "FETCH",
"inputStage" : {
"stage" : "OR",
"inputStages" : [
{
"stage" : "IXSCAN",
"keyPattern" : {
"first" : 1,
"last" : 1
},
"indexName" : "first_1_last_1",
"isMultiKey" : false,
"multiKeyPaths" : {
"first" : [ ],
"last" : [ ]
},
"isUnique" : true,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"first" : [
"[\"Alice\", \"Alice\"]"
],
"last" : [
"[\"Brown\", \"Brown\"]"
]
}
},
{
"stage" : "IXSCAN",
"keyPattern" : {
"first" : 1,
"last" : 1
},
"indexName" : "first_1_last_1",
"isMultiKey" : false,
"multiKeyPaths" : {
"first" : [ ],
"last" : [ ]
},
"isUnique" : true,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"first" : [
"[\"Bob\", \"Bob\"]"
],
"last" : [
"[\"White\", \"White\"]"
]
}
}
]
}
}
}
You can see that the index is properly utilized in $or query and not used in the $in query.

Answer 2

For this mysql query
SELECT * FROM names
WHERE (first = 'Alice' AND last = 'Brown')
OR (first = 'Bob' AND last = 'White')
OR ...
can be use in mongodb as
db.names.find({
$or: [
{ first: "Alice", last: "Brown" },
{ first: "Bob", last: "White" },
...
]})
For below mysql query
SELECT * FROM names
WHERE (first, last) IN (('Alice', 'Brown'), ('Bob','White') OR ...)
You can not create mongodb $in query
db.names.find({
$or: [
{ first: { $in: ["John", "Alice", "Bob"] } },
{ last: { $in: ["Smith", "Johnson", "Williams" ] } },
]})
Because it pass this result too
("John", "Johnson"),("John", "Williams"),("John", "Smith"),("John", "Williams")..
the best way is $or as ask in question
db.names.find({
$or: [
{ first: "Alice", last: "Brown" },
{ first: "Bob", last: "White" },
...
]})
May be better solution present out there. I will update my answer if find any. Thanks

Answer 3

Yes, it's possible to use $in to query MongoDb collections based on multiple values.
Try using the below syntax:
db.names.find.({ field: { $in: [<value1>, <value2>, ... <valueN> ] } })
for example in your case it looks like:
db.names.find({first: {$in: ["Alice","Brown","Bob", "White"]}})