MongoDBRead

MongoDBRead performs read operations on a Mongo database.

Use ‘Row by row’ under ‘Return options’ for large datasets.

Properties

  • Collection

    The collection to read from.

  • Connection string

    A connection string to your database.

  • Fields

    Specifies which fields to return. Format is

    { field1: value, field2: value ... }

    where field = the field name and value = 1 to include and 0 to exclude. The parameter contains either include or exclude specifications, not both, unless the exclude is for the _id field.

  • Limit

    An integer indicating the maximum number of documents to return.

  • Pipelines

    Available when Operation = Aggregate.

    The aggregation pipelines should be specified as a JSON formatted array of aggregation objects.

    For example, if we have a collection of "People" documents with attributes "age" and "name", the aggregation pipeline:

    [     {          $sort: { age: -1 }      },     {          $group: {             total: { $sum: 1 },              eldest: { $first: "$name"}          }     }, ]

    will sort the documents in the collection by age, and group the results into a single document with attributes "total" (containing the total number of records in the collection) and "eldest" (the "name" attribute of the document with the greatest "age").

    More information on MongoDb’s aggregation pipeline and operations can be found here.

    An editor is provided to add database fields and variables to the aggregation pipeline.

  • Query

    A MongoDb query document. For example, if we select from a collection of documents with attributes "quantity" and "price", the criteria:

    {      $or: [             { quantity: { $gt: 100 } },             { price: { $lt: 9.95 } }         ] }

    will return all documents in the collection with fields "quantity" greater than 100 or "price" less than 9.95.

    More information can be found here.

  • Skip

    An integer indicating how many documents to skip before returning results.

  • Sort

    Specifies the order in which the query returns matching documents. Format is

    { field1: value, field2: value ... }

    where field = the field name and value = 1 to sort ascending and -1 to sort descending.

  • Operation

    • Find Selects documents in a collection.

    • Aggregate Calculates aggregate values for the data in a collection.
  • Output type

    The custom type that will be used to store the results from the database. The names of the fields in the custom type should match the field names of the documents returned from MongoDb.

    The custom type can optionally include a string field named "id" which will be populated by the document’s unique id attribute.

  • Return options

    • First row
      The function will return the first document returned by the query. If no data is returned by the query, an error will be reported.
    • First row, else empty row
      The function will return the first document returned by the query. If no data is returned by the query, the function will return a document containing default values.
    • List of rows
      The function will return all documents in one list. The list can then be used later in the process without having to execute the query again.
    • Row by row
      The function will automatically return one document at a time. You will see a "ForEachRow" loop icon as a child of this function. Any function you attach to the results will be inside of the loop. This is recommended whenever you expect to retrieve multiple items, but you don’t need the complete list of items all at once.

ID Attributes

Each document in a Mongo collection is uniquely identified by an Object ID field called "_id". When reading from the database, it is possible to retrieve this id by adding a string field named "id" or "_id" to the custom type specified in the return type property.

When using the object id as an element in the Query property, the string value will need to be converted back into a mongo object id. For example, a document with id "525bc19331eec126ecdcf199" can be retrieved using the query:

{      _id: ObjectId("525bc19331eec126ecdcf199") }

Links