Query DSL

Casbah provides a rich fluid query syntax, that allows you to construct DBObjects on the fly using MongoDB query operators.

Query Selectors

Comparison Operators

$all Matches arrays that contain all elements specified:
```
"size" $all ("S", "M", "L")
```
$eq Matches values that are equal to the value specified:
```
"price" $eq 10
```
$gt Matches values that are greater than the value specified in the query
$gte Matches values that are equal to or greater than the value specified:
```
"price" $gt 10
"price" $gte 10
```
$in Matches any of the values that exist in an array specified:
```
"size" $in ("S", "M", "L")
```
$lt Matches values that are less than the value specified in the query
$lte Matches values that are less than or equal to the value specified:
```
"price" $lt 100
"price" $lte 100
```
$ne Matches all values that are not equal to the value specified:
```
"price" $ne 1000
```
$nin Matches values that do not exist in an array specified:
```
"size" $nin ("S", "XXL")
```

Logical Operators

$or Joins query clauses with a logical OR returns all documents that match the conditions of either clause:
```
$or( "price" $lt 5 $gt 1, "promotion" $eq true )
$or( ( "price" $lt 5 $gt 1 ) :: ( "stock" $gte 1 ) )
```
$and Joins query clauses with a logical AND returns all documents that match the conditions of both clauses:
```
$and( "price" $lt 5 $gt 1, "stock" $gte 1 )
$and( ( "price" $lt 5 $gt 1 ) :: ( "stock" $gte 1 ) )
```
$not Inverts the effect of a query expression and returns documents that do not match the query expression:
```
"price" $not { _ $gte 5.1 }
```

$nor Joins query clauses with a logical NOR returns all documents that fail to match both clauses:

$nor( "price" $eq 1.99 , "qty" $lt 20, "sale" $eq true )
$nor( ( "price" $lt 5 $gt 1 ) :: ( "stock" $gte 1 ) )

Element Operators

$exists Matches documents that have the specified field:
```
"qty" $exists true
```
$mod Performs a modulo operation on the value of a field and selects documents with a specified result:
```
"qty" $mod (5, 0)
```
$type Selects documents if a field is of the specified type:
```
"size".$type[BasicDBList]
```

JavaScript Operators

$where Matches documents that satisfy a JavaScript expression:
```
$where("function () { this.credits == this.debits }")
```
$regex Selects documents where values match a specified regular expression. You can also use native regular expressions:
```
"foo" $regex "^bar$"
"foo" $eq "^bar$".r
```

Geospatial Operators

$geoWithin Selects geometries within a bounding GeoJSON geometry:

// Create a GeoJson geometry document
var geo = MongoDBObject("$geometry" ->
        MongoDBObject("$type" -> "polygon",
          "coordinates" -> (((GeoCoords(74.2332, -75.23452),
                              GeoCoords(123, 456),
                              GeoCoords(74.2332, -75.23452))))))


// Example $geoWithin Queries
"location" $geoWithin(geo)
"location" $geoWithin $box ((74.2332, -75.23452), (123, 456))
"location" $geoWithin $center ((50, 50), 10)
"location" $geoWithin $centerSphere ((50, 50), 10)

$geoIntersects Selects geometries that intersect with a GeoJSON geometry:

// Create a GeoJson geometry document
var geo = MongoDBObject("$geometry" ->
            MongoDBObject("$type" -> "polygon",
              "coordinates" -> (((GeoCoords(74.2332, -75.23452),
                                  GeoCoords(123, 456),
                                  GeoCoords(74.2332, -75.23452))))))
val near = "location" $geoIntersects geo

$near Returns geospatial objects in proximity to a point:
```
"location" $near (74.2332, -75.23452)
```
$nearSphere Returns geospatial objects in proximity to a point on a sphere:
```
"location" $nearSphere (74.2332, -75.23452)
```

Array Query Operators

$elemMatch Selects documents if element in the array field matches all the specified $elemMatch conditions:
```
"colour" $elemMatch (MongoDBObject("base" -> "red", "flash" -> "silver")
```
$size Selects documents if the array field is a specified size:
```
"comments" $size 12
```

Update DSL Operators

Field Operators

$inc Increments the value of the field by the specified amount:
```
$inc("sold" -> 1, "stock" -> -1)
```

$rename Renames a field:

$rename("color" -> "colour", "realize" -> "realise")

$setOnInsert Sets the value of a field upon documentation creation during an upsert. Has no effect on update operations that modify existing documents:
```
$setOnInsert("promotion" -> "new")
```
$set Sets the value of a field in an existing document:
```
$set("promotion" -> "sale", "qty" -> 100)
```
$unset Removes the specified field from an existing document:
```
$unset("promotion")
```
$currentDate Updates the specified fields to current server-side date or timestamp (the only allowed values):
```
$currentDate("lastUpdated" -> "date", "ts" -> "timestamp")
```

Array Update Operators

$addToSet Adds elements to an existing array only if they do not already exist in the set:

$addToSet("sizes" -> "L", "colours" -> "Blue")
$addToSet("sizes") $each ("S", "M", "L", "XL")

$pop Removes the first or last item of an array:
```
$pop("sizes" -> "L")
```
$pull Removes items from an array that match a query statement:
```
$pull("sizes" -> "L")
$pull("widgets" $gt 2 )
```
$pullAll Removes multiple values from an array:
```
$pullAll("sizes" -> ("S", "XL"))
```

$push Adds an item to an array:

$push("sizes" -> "L")
$push("widgets" $gt 2 )
$push("sizes") $each ("S", "M", "L", "XL")

$pushAll Deprecated. Adds several items to an array:
```
$pushAll("sizes" -> ("S", "XL"))
```

Bitwise Operators

$bit Performs bitwise AND and OR updates of integer values:
```
$bit("foo") and 5
```

For the full query syntax to MongoDB see the core docs at: docs.mongodb.org

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