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How-To: Query state
alpha
The state query API is in alpha stage.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 entries:
filtersortpage
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:
keyis a key in the state storeorderis 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.
limitsets the page size.tokenis 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:
keyis the unique IDvalueis 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 --resources-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.
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.
Related links
- Refer to the query API reference.
- See the state store components that implement query support.
- View the state store query API implementation guide.
- See how to query Redis state store.
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