Casbah (Scala) Generating a query statement with nested conditions ($OR $AND)

Question

Given items: [{ prop1 : "a", prop2 : "b" , prop3, "c",....},....] and patterns:[{ prop1 : "a", prop2 : "Any"},...]

I want to create a query to find all patterns that match the given items.

The resulting query is of form:

((A or B or C) AND (D or E or F) AND (G or H or J))
or
((A or B or C) AND (D or E or F) AND (G or H or J))
or
((A or B or C) AND (D or E or F) AND (G or H or J))
....

I've tried to build a DSL-form , but I get an ambiguous implicit error on the init:

Can this notation be used? Or how could I implement this with DBObject.Builder or MongoDbObjects?

Thanks, Eli

import com.mongodb.casbah.query.Imports._

/* test data */
val thing1 = Map[String,String]("thing_type" -> "PC", "os"-> "Windows", "vendor"-> "lenova")
val thing2 = Map[String,String]("thing_type" -> "Tablet", "os"-> "iOS", "vendor"-> "Apple")
"

val things_list = List(thing1, thing2)
/* end test data */

val atts_for_search = List("thing_type", "os", "vendor" )
var pattern_query = $or()                      // *causes a compilation error
things_list.foreach ( thing => {
    var att_and_list = $and()               // *causes a compilation error
    atts_for_search.foreach ( att => {
          att_and_list ++= $or(att $eq thing(att),att $exists false,att $eq "Any")

    }) // foreach attribute
    pattern_query  ++= att_and_list
})

score 0 · Answer 1 · answered May 15 '15 at 16:12

The $or and $and parts of the dsl require a traversable and can't initiated without one - hence the compile error.

If you can just delay the creation of the $and and $or parts of the query until you have built the traversable it works:

import com.mongodb.casbah.query.Imports._

/* test data */
val thing1 = Map[String,String]("thing_type" -> "PC", "os"-> "Windows", "vendor"-> "lenova")
val thing2 = Map[String,String]("thing_type" -> "Tablet", "os"-> "iOS", "vendor"-> "Apple")
val things_list = List(thing1, thing2)
/* end test data */

val atts_for_search = List("thing_type", "os", "vendor" )
val ors = scala.collection.mutable.ListBuffer[DBObject]()
things_list.foreach ( thing => {
    var ands = scala.collection.mutable.ListBuffer[DBObject]()
    atts_for_search.foreach ( att => {
          ands += $or(att $eq thing(att),att $exists false,att $eq "Any")

    }) // foreach attribute
    ands  += $and(ands)
})
val pattern_query = $or(ors)

This returns the following output:

{"$or": [{ "$and": [{ "$or": [ { "thing_type" : "PC"} , { "thing_type" : { "$exists" : false}} , { "thing_type" : "Any"}]} , 
                    { "$or": [ { "os" : "Windows"} , { "os" : { "$exists" : false}} , { "os" : "Any"}]} , 
                    { "$or": [ { "vendor" : "lenova"} , { "vendor" : { "$exists" : false}} , { "vendor" : "Any"}]}]} , 
         { "$and": [{ "$or": [ { "thing_type" : "Tablet"} , { "thing_type" : { "$exists" : false}} , { "thing_type" : "Any"}]} , 
                    { "$or": [ { "os" : "iOS"} , { "os" : { "$exists" : false}} , { "os" : "Any"}]} , 
                    { "$or": [ { "vendor" : "Apple"} , { "vendor" : { "$exists" : false}} , { "vendor" : "Any"}]}]}]}

Casbah (Scala) Generating a query statement with nested conditions ($OR $AND)

1 Answers1