Query Basics

MVOM allows consumers to execute queries against the database via the defined schema associated with a Model instance. Queries are constructed using MVOM's query language which are then translated into MultiValue queries. The results of the query are then returned as Model instances. MVOM exposes two static methods for issuing queries: find and findAndCount.

find Method

The find method accepts an MVOM query condition object and returns an array of Model instances which matched the query's conditions.

Syntax

static find(queryCondition: Filter, options?: ModelFindOptions): Promise<Model[]>

Parameters

Parameter	Type	Description
queryCondition	object	The query condition filter object
options	object	Options object

Options Object Properties

Property	Type	Description
skip	number	The number of matching records to skip when returning results. See pagination.
limit	number	The number of matching records to return in the result set. See pagination.
sort	[string, -1 | 1 ][]	The sort criteria for the query. See sorting.
projection	string[]	The projection of properties to return from the database
maxReturnPayloadSize	number	The maximum allowed return payload size in bytes. If this size is exceeded a DbServerError will be thrown. If omitted the value specified during connection creation is used.
requestId	string	A request/trace ID to be passed to MVIS as a request header with the key X-MVIS-Trace-Id
userDefined	object	The user defined options to pass to the database subroutines

findAndCount Method

The findAndCount method accepts an MVOM query condition object and returns an array of Model instances which matched the query's conditions as well as a count of the total number of records which matched the query's conditions. This count value can be useful when executing paginated queries.

Syntax

static findAndCount(queryCondition: Filter, options?: ModelFindOptions): Promise<ModelFindAndCountResult>

Parameters

The parameters for findAndCount are the same as for find.

Return Value

The return value of findAndCount is an object with the following properties:

Property	Type	Description
count	number	The total number of records which matched the query condition
documents	Model[]	The Model instances which were returned by the query

The Query Condition Filter Object

When issuing queries, a query condition filter object must be passed to the find or findAndCount methods. This query condition filter object has properties which correspond to the properties of the Schema which are assigned values which define the condition for the query. The general format of a query condition filter object is:

{
  propertyName1: {
    conditionalOperator: conditionalValue,
  },
  propertyName2: {
    conditionalOperator: conditionalValue,
  }
}

info

In order to use a property for a query it must either be a property defined in the schema with a specified dictionary value or a property defined in the dictionaries object of the schema options.

Example

Consider a scenario where you want to query for all items which have a price greater than 100. The following example code illustrates construction of a query to satisfy that requirement.

const schema = new Schema({
  description: { type: 'string', path: 1, dictionary: 'DESCRIPTION' },
  price: { type: 'number', path: 2, dbDecimals: 2, dictionary: 'PRICE' },
});

const Item = connection.model(schema, 'ITEM');

const items = await Item.find({ price: { $gt: 100 } });

In the above example, price is the schema property which is being queried against. $gt is the greater than operator and 100 is the value to be compared.

The query which will be executed on the MultiValue database is:

select ITEM with PRICE > "100"

tip

If you provide a logger to your Connection, the transformed MultiValue query will be passed to the debug method.