Filtering results

Orion Context Broker implements several filters that can be used to filter the results in NGSI10 query operations. These filters are typically used with queryContext with patterns or the convenience operation to get all entities.

As a general rule, filters used in standard operation use a scope element:

  (curl localhost:1026/v1/queryContext -s -S --header 'Content-Type: application/json' --header 'Accept: application/json' -d @- | python -mjson.tool) <<EOF
  {
  "entities": [
      {
      "type": "myEntityType",
      "isPattern": "true",
      "id": ".*"
      }
  ],
  "restriction": {
      "scopes": [
      {
          "type": "FIWARE::Filter::foobar",
          "value": ""
      }
      ]
  }
  }
  EOF

while filters in convenience operations are included as parameters in the URL:

curl localhost:1026/v1/contextEntities?filter=value -s -S --header 'Content-Type: application/json' --header 'Accept: application/json' | python -mjson.tool

Filters are cumulative. In other words, you can use several scopes in the same restriction (in the case of standard operations) or several URL argument separated by '&' in order to specify several filters. The result is a logic "and" between all of them.

Existence type filter

The scope correspoding to this type is "FIWARE::Filter::Existence".

  ...                                                           
  {
  "restriction": {
      "scopes": [
      {
          "type": "FIWARE::Filter::Existence",
          "value": "entity::type"
      }
      ]
  }
  }
  ...

The URL parameter corresponding to this filter is 'exist'.

curl localhost:1026/v1/contextEntities?exist=entity::type ...

In the current version, the only parameter than can be checked for existence is the entity type, corresponding to "entity::type".

No-Existence type filter

The scope corresponding to this type is "FIWARE::Filter::Not::Existence".

  ...                                                                
  {
  "restriction": {
      "scopes": [
      {
          "type": "FIWARE::Filter::Not::Existence",
          "value": "entity::type"
      }
      ]
  }
  }
  ...

The URL parameter corresponding to this filter is '!exist'.

curl localhost:1026/v1/contextEntities?!exist=entity::type ...

In the current version, the only parameter than can be checked for no-existence is the entity type, corresponding to "entity::type". Note that this is the only way of selecting an "entity without type" (given that queries without type resolve to "any type", as explained in the following section).

Entity type filter

There is no scope corresponding to this filter, given that you can use the usual entity type:

---

JSON

---

  ...                                            
  {
  "type": "Room",
  "isPattern": "...",
  "id": "..."
  }
  ...

---

The URL parameter corresponding to this filter is 'entity::type'.

curl localhost:1026/v1/contextEntities?entity::type=Room ...

Geo-location filter

The scope corresponding to this type is "FIWARE::Location". It is described in detail in the following section.

In the current version of Orion, there is no equivalent convenience operation filter.