Making search queries

Clients can make GET requests on individual instances of a model (for example, GET /api/person/1) and on collections of all instances of a model (GET /api/person). To get all instances of a model which meet some criteria, clients can make GET requests with a query parameter specifying a search. The search functionality in Flask-Restless is relatively simple, but should suffice for many cases.

If the allow_patch_many keyword argument is set to True when calling the APIManager.create_api() function, then PATCH requests will accept search queries as well. In this case, every instance of the model which meets the criteria of the search will be patched. For more information, see Enabling patching the result of a search.

Query format

The query parameter q must be a JSON string. It can have the following mappings, all of which are optional:

filters

A list of objects of one of the following forms:

{"name": <fieldname>, "op": <operatorname>, "val": <argument>}

or:

{"name": <fieldname>, "op": <operatorname>, "field": <fieldname>}

In the first form, <operatorname> is one of the strings described in the Operators section, the first <fieldname> is the name of the field of the model to which to apply the operator, <argument> is a value to be used as the second argument to the given operator. In the second form, the second <fieldname> is the field of the model which should be used as the second argument to the operator.

<fieldname> may alternately specify a field on a related model, if it is a string of the form <relationname>__<fieldname>.

The returned list of matching instances will include only those instances which satisfy all of the given filters.

limit

A positive integer which specified the maximum number of objects to return.

offset

A positive integer which specifies the offset into the result set of the returned list of instances.

order_by

A list of objects of the form:

{"field": <fieldname>, "direction": <directionname>}

where <fieldname> is a string corresponding to the name of a field of the requested model and <directionname> is either "asc" for ascending order or "desc" for descending order.

single

A boolean representing whether a single result is expected as a result of the search. If this is true and either no results or multiple results meet the criteria of the search, the server responds with an error message.

Operators

The operator strings recognized by the API incude:

• ==, eq, equals, equals_to
• !=, neq, does_not_equal, not_equal_to
• >, gt, <, lt
• >=, ge, gte, geq, <=, le, lte, leq
• in, not_in
• is_null, is_not_null
• like
• has
• any

These correspond to SQLAlchemy column operators as defined here.

Examples

Consider a Person model available at the URL /api/person, and suppose all of the following requests are GET /api/person requests with query parameter q.

Attribute greater than a value

If query parameter q has the value

{"filters": [{"name": "age", "op": "ge", "val": 10}]}

(represented as a string), then the response will include only those Person instances which have age attribute greater than or equal to 10.

HTTP/1.1 200 OK

{ "objects":
  [
    {"id": 1, "name": "Jeffrey", "age": 24},
    {"id": 2, "name": "John", "age": 13},
    {"id": 3, "name": "Mary", "age": 18}
  ]
}

Attribute between two values

If query parameter q has the value

{ "filters":
  [
    {"name": "age", "op": "ge", "val": 10},
    {"name": "age", "op": "le", "val": 20}
  ]
}

(represented as a string), then the response will include only those Person instances which have age attribute between 10 and 20, inclusive.

HTTP/1.1 200 OK

{ "objects":
  [
    {"id": 2, "name": "John", "age": 13},
    {"id": 3, "name": "Mary", "age": 18}
  ]
}

Expecting a single result

If query parameter q has the value

{
  "single": true,
  "filters":
  [
    {"name": "id", "op": "eq", "val": 1}
  ]
}

(represented as a string), then the response will the sole Person instance with id equal to 1.

HTTP/1.1 200 OK

{"id": 1, "name": "Jeffrey", "age": 24}

In the case that the search would return no results or more than one result, an error response is returned instead.

{
  "single": true,
  "filters":
  [
    {"name": "age", "op": "ge", "val": 10}
  ]
}

HTTP/1.1 400 Bad Request

{"message": "Multiple results found"}

{
  "single": true,
  "filters":
  [
    {"name": "id", "op": "eq", "val": -1}
  ]
}

HTTP/1.1 400 Bad Request

{"message": "No result found"}

Comparing two attributes

If query parameter q has the value

{"filters": [{"name": "age", "op": "ge", "field": "height"}]}

(represented as a string), then the response will include only those Person instances which have age attribute greater than or equal to the value of the height attribute.

HTTP/1.1 200 OK

{ "objects":
  [
    {"id": 1, "name": "John", "age": 80, "height": 65},
    {"id": 2, "name": "Mary", "age": 73, "height": 60}
  ]
}

Comparing attribute of a relation

If query parameter q has the value

{ "filters":
  [
    {"name": "computers__manufacturer", "val": "Dell", "op": "any"}
  ]
}

(represented as a string), then the response will include only those Person instances which are related to any Computer model which is manufactured by Apple.

HTTP/1.1 200 OK

{ "objects": [
    {
      "id": 1,
      "name": "John",
      "computers": [
        { "id": 1, "manufacturer": "Dell", "model": "Inspiron 9300"},
        { "id": 2, "manufacturer": "Apple", "model": "MacBook"}
      ]
    },
    {
      "id": 2,
      "name": "Mary",
      "computers": [
        { "id": 3, "manufacturer": "Apple", "model": "iMac"}
      ]
    }
  ]
}