MongoDb

Queries

find

• find({field:value}) // finde Objekt mit field === value)
• find({field: {$exists: true/false} }) // finde Objekt, dass Feld (nicht) hat
• pattern:
  • find({value: /pattern/})
• { $and: [ { expression1 }, { expression2 } , ... , { expressionN } ] }

update

• update({field:value}, {$set:{somefield:someValue}})
• update({field:value}, {$set:{somefield:someValue}}, false, true) // multiupdate

db.collection.update(
   <query>,
   <update>,
   {
     upsert: <boolean>,
     multi: <boolean>,
     writeConcern: <document>,
     collation: <document>,
     arrayFilters: [ <filterdocument1>, ... ],
     hint:  <document|string>        // Available starting in MongoDB 4.2
   }
)

Field comparsion

({$where:"this.fieldA == this.fieldB"})
({$where:"this.fieldA != this.fieldB"})
({$where:"this.fieldA >= this.fieldB"})

DateRange

{ 
  someDateField: {
    $gte:IsoDate(y-m-dTH:M:S),
    $lt:IsoDate(y-m-dTH:M:S)
  }
}

Indexing

index key ordering, blog

• Equality tests, in any order
• Sort fields, in the order requested by the query
• Range filters, in increasing order of cardinality

Java

Testing

• Mock mongoDb driver

• Query Unit tests