Basic

This page describes basic queries and how to create a new query policy.

Basic queries

Basic queries are read-only queries that return records to the client. A client application makes an API request to start a read-only query. This request in turn initiates parallel requests to each node in the cluster. The result returns the current version of each record to the client.

Policies

Query policies can be passed on a per-request basis. Policy values can be set to create a filter expression, to determine whether bin data is included with the response, identify a short versus long query, and more.

The following example creates a new query policy that defines a Filter Expression that compares the length of the shape list in the report map and returns true if greater than 2.

// Create a query policy with Filter Expression
QueryPolicy queryPolicy = new QueryPolicy();
queryPolicy.filterExp = Exp.Build(
    Exp.GT
        ListExp.Size(
            MapExp.GetByKey(
                MapReturnType.VALUE,
                Exp.Type.LIST,
                Exp.Val("shape"),
                Exp.MapBin("report"))
        ),
        Exp.Val(2)
    )
);