How-To: Query state

Use the Query API for querying state stores

With the state query API, you can retrieve, filter, and sort the key/value data stored in state store components. The query API is not a replacement for a complete query language.

Even though the state store is a key/value store, the value might be a JSON document with its own hierarchy, keys, and values. The query API allows you to use those keys/values to retrieve corresponding documents.

Querying the state

Submit query requests via HTTP POST/PUT or gRPC. The body of the request is the JSON map with 3 optional entries:

  • filter
  • sort
  • page

filter

The filter specifies the query conditions in the form of a tree, where each node represents either unary or multi-operand operation.

The following operations are supported:

Operator Operands Description
EQ key:value key == value
IN key:[]value key == value[0] OR key == value[1] OR … OR key == value[n]
AND []operation operation[0] AND operation[1] AND … AND operation[n]
OR []operation operation[0] OR operation[1] OR … OR operation[n]

The key in the operand is similar to the JSONPath notation. Each dot in the key indicates a nested JSON structure. For example, consider this structure:

{
  "shape": {
    "name": "rectangle",
    "dimensions": {
      "height": 24,
      "width": 10
    },
    "color": {
      "name": "red",
      "code": "#FF0000"
    }
  }
}

To compare the value of the color code, the key will be shape.color.code.

If the filter section is omitted, the query returns all entries.

sort

The sort is an ordered array of key:order pairs, where:

  • key is a key in the state store
  • order is an optional string indicating sorting order:
    • "ASC" for ascending
    • "DESC" for descending
      If omitted, ascending order is the default.

page

The page contains limit and token parameters.

  • limit sets the page size.
  • token is an iteration token returned by the component, used in subsequent queries.

Behind the scenes, this query request is translated into the native query language and executed by the state store component.

Example data and query

Let’s look at some real examples, ranging from simple to complex.

As a dataset, consider a collection of employee records containing employee ID, organization, state, and city. Notice that this dataset is an array of key/value pairs, where:

  • key is the unique ID
  • value is the JSON object with employee record.

To better illustrate functionality, organization name (org) and employee ID (id) are a nested JSON person object.

Get started by creating an instance of MongoDB, which is your state store.

docker run -d --rm -p 27017:27017 --name mongodb mongo:5

Next, start a Dapr application. Refer to the component configuration file, which instructs Dapr to use MongoDB as its state store.

dapr run --app-id demo --dapr-http-port 3500 --components-path query-api-examples/components/mongodb

Populate the state store with the employee dataset, so you can query it later.

curl -X POST -H "Content-Type: application/json" -d @query-api-examples/dataset.json http://localhost:3500/v1.0/state/statestore

Once populated, you can examine the data in the state store. In the image below, a section of the MongoDB UI displays employee records.

Sample dataset

Each entry has the _id member as a concatenated object key, and the value member containing the JSON record.

The query API allows you to select records from this JSON structure.

Now you can run the example queries.

Example 1

First, find all employees in the state of California and sort them by their employee ID in descending order.

This is the query:

{
    "filter": {
        "EQ": { "state": "CA" }
    },
    "sort": [
        {
            "key": "person.id",
            "order": "DESC"
        }
    ]
}

An equivalent of this query in SQL is:

SELECT * FROM c WHERE
  state = "CA"
ORDER BY
  person.id DESC

Execute the query with the following command:


curl -s -X POST -H "Content-Type: application/json" -d @query-api-examples/query1.json http://localhost:3500/v1.0-alpha1/state/statestore/query | jq .

Invoke-RestMethod -Method Post -ContentType 'application/json' -InFile query-api-examples/query1.json -Uri 'http://localhost:3500/v1.0-alpha1/state/statestore/query'

The query result is an array of matching key/value pairs in the requested order:

{
  "results": [
    {
      "key": "3",
      "data": {
        "person": {
          "org": "Finance",
          "id": 1071
        },
        "city": "Sacramento",
        "state": "CA"
      },
      "etag": "44723d41-deb1-4c23-940e-3e6896c3b6f7"
    },
    {
      "key": "7",
      "data": {
        "city": "San Francisco",
        "state": "CA",
        "person": {
          "id": 1015,
          "org": "Dev Ops"
        }
      },
      "etag": "0e69e69f-3dbc-423a-9db8-26767fcd2220"
    },
    {
      "key": "5",
      "data": {
        "state": "CA",
        "person": {
          "org": "Hardware",
          "id": 1007
        },
        "city": "Los Angeles"
      },
      "etag": "f87478fa-e5c5-4be0-afa5-f9f9d75713d8"
    },
    {
      "key": "9",
      "data": {
        "person": {
          "org": "Finance",
          "id": 1002
        },
        "city": "San Diego",
        "state": "CA"
      },
      "etag": "f5cf05cd-fb43-4154-a2ec-445c66d5f2f8"
    }
  ]
}

Example 2

Now, find all employees from the “Dev Ops” and “Hardware” organizations.

This is the query:

{
    "filter": {
        "IN": { "person.org": [ "Dev Ops", "Hardware" ] }
    }
}

An equivalent of this query in SQL is:

SELECT * FROM c WHERE
  person.org IN ("Dev Ops", "Hardware")

Execute the query with the following command:


curl -s -X POST -H "Content-Type: application/json" -d @query-api-examples/query2.json http://localhost:3500/v1.0-alpha1/state/statestore/query | jq .

Invoke-RestMethod -Method Post -ContentType 'application/json' -InFile query-api-examples/query2.json -Uri 'http://localhost:3500/v1.0-alpha1/state/statestore/query'

Similar to the previous example, the result is an array of matching key/value pairs.

Example 3

In this example, find:

  • All employees from the “Dev Ops” department.
  • Employees from the “Finance” departing residing in the states of Washington and California.

In addition, sort the results first by state in descending alphabetical order, then by employee ID in ascending order. Let’s process up to 3 records at a time.

This is the query:

{
    "filter": {
        "OR": [
            {
                "EQ": { "person.org": "Dev Ops" }
            },
            {
                "AND": [
                    {
                        "EQ": { "person.org": "Finance" }
                    },
                    {
                        "IN": { "state": [ "CA", "WA" ] }
                    }
                ]
            }
        ]
    },
    "sort": [
        {
            "key": "state",
            "order": "DESC"
        },
        {
            "key": "person.id"
        }
    ],
    "page": {
        "limit": 3
    }
}

An equivalent of this query in SQL is:

SELECT * FROM c WHERE
  person.org = "Dev Ops" OR
  (person.org = "Finance" AND state IN ("CA", "WA"))
ORDER BY
  state DESC,
  person.id ASC
LIMIT 3

Execute the query with the following command:


curl -s -X POST -H "Content-Type: application/json" -d @query-api-examples/query3.json http://localhost:3500/v1.0-alpha1/state/statestore/query | jq .

Invoke-RestMethod -Method Post -ContentType 'application/json' -InFile query-api-examples/query3.json -Uri 'http://localhost:3500/v1.0-alpha1/state/statestore/query'

Upon successful execution, the state store returns a JSON object with a list of matching records and the pagination token:

{
  "results": [
    {
      "key": "1",
      "data": {
        "person": {
          "org": "Dev Ops",
          "id": 1036
        },
        "city": "Seattle",
        "state": "WA"
      },
      "etag": "6f54ad94-dfb9-46f0-a371-e42d550adb7d"
    },
    {
      "key": "4",
      "data": {
        "person": {
          "org": "Dev Ops",
          "id": 1042
        },
        "city": "Spokane",
        "state": "WA"
      },
      "etag": "7415707b-82ce-44d0-bf15-6dc6305af3b1"
    },
    {
      "key": "10",
      "data": {
        "person": {
          "org": "Dev Ops",
          "id": 1054
        },
        "city": "New York",
        "state": "NY"
      },
      "etag": "26bbba88-9461-48d1-8a35-db07c374e5aa"
    }
  ],
  "token": "3"
}

The pagination token is used “as is” in the subsequent query to get the next batch of records:

{
    "filter": {
        "OR": [
            {
                "EQ": { "person.org": "Dev Ops" }
            },
            {
                "AND": [
                    {
                        "EQ": { "person.org": "Finance" }
                    },
                    {
                        "IN": { "state": [ "CA", "WA" ] }
                    }
                ]
            }
        ]
    },
    "sort": [
        {
            "key": "state",
            "order": "DESC"
        },
        {
            "key": "person.id"
        }
    ],
    "page": {
        "limit": 3,
        "token": "3"
    }
}

curl -s -X POST -H "Content-Type: application/json" -d @query-api-examples/query3-token.json http://localhost:3500/v1.0-alpha1/state/statestore/query | jq .

Invoke-RestMethod -Method Post -ContentType 'application/json' -InFile query-api-examples/query3-token.json -Uri 'http://localhost:3500/v1.0-alpha1/state/statestore/query'

And the result of this query is:

{
  "results": [
    {
      "key": "9",
      "data": {
        "person": {
          "org": "Finance",
          "id": 1002
        },
        "city": "San Diego",
        "state": "CA"
      },
      "etag": "f5cf05cd-fb43-4154-a2ec-445c66d5f2f8"
    },
    {
      "key": "7",
      "data": {
        "city": "San Francisco",
        "state": "CA",
        "person": {
          "id": 1015,
          "org": "Dev Ops"
        }
      },
      "etag": "0e69e69f-3dbc-423a-9db8-26767fcd2220"
    },
    {
      "key": "3",
      "data": {
        "person": {
          "org": "Finance",
          "id": 1071
        },
        "city": "Sacramento",
        "state": "CA"
      },
      "etag": "44723d41-deb1-4c23-940e-3e6896c3b6f7"
    }
  ],
  "token": "6"
}

That way you can update the pagination token in the query and iterate through the results until no more records are returned.

Limitations

The state query API has the following limitations:

  • To query actor states stored in a state store, you need to use the query API for the specific database. See querying actor state.
  • The API does not work with Dapr encrypted state stores capability. Since the encryption is done by the Dapr runtime and stored as encrypted data, then this effectively prevents server side querying.

You can find additional information in the related links section.


Last modified September 14, 2022: Upmerge to 1.9 (#2793) (a35f0dcd)