How to work with the API - An example

Note

The API is enable for the following schmemas only:

  • model_draft
  • sandbox

Authenticate

The OpenEnergy Platform API uses token authentication. Each user has a unique token assigned to it that will be used as an authentication password. You can access you token by visiting you profile on the OEP. In order to issue PUT or POST request you have to include this token in the Authorization-field of your request:

  • Authorization: Token your-token

Create table

We want to create the following table with primary key id:

In order to do so, we send the following PUT request:

PUT oep.iks.cs.ovgu.de/api/v0/schema/sandbox/tables/example_table/
{
    "query": {
        "columns": [
            {
                "name":"id",
                "data_type": "Bigserial",
                "is_nullable": "NO"
            },{
                "name":"name",
                "data_type": "varchar",
                "character_maximum_length": "50"
            },{
                "name":"geom",
                "data_type": "geometry(point)"
            }
        ],
        "constraints": [
            {
                "constraint_type": "PRIMARY KEY",
                "constraint_parameter": "id",
            }
        ]
    }
}

and include the following headers:

  • Content-Type: application/json
  • Authorization: Token your-token

You can use any tool that can send HTTP-requests. E.g. you could use the linux tool curl:

curl
    -X PUT
    -H 'Content-Type: application/json'
    -H 'Authorization: Token <your-token>'
    -d '{
            "query": {
                "columns": [
                    {
                        "name":"id",
                        "data_type": "bigsersial",
                        "is_nullable": "NO"
                    },{
                        "name":"name",
                        "data_type": "varchar",
                        "character_maximum_length": "50"
                    },{
                        "name":"geom",
                        "data_type": "geometry(point)"
                    }
                ],
                "constraints": [
                    {
                        "constraint_type": "PRIMARY KEY",
                        "constraint_parameter": "id",
                    }
                ]
            }
        }'
    oep.iks.cs.ovgu.de/api/v0/schema/sandbox/tables/example_table/

or python:

>>> import requests
>>> data = { "query": { "columns": [ { "name":"id", "data_type": "bigserial", "is_nullable": "NO" },{ "name":"name", "data_type": "varchar", "character_maximum_length": "50" },{ "name":"geom", "data_type": "geometry(point)" } ], "constraints": [ { "constraint_type": "PRIMARY KEY", "constraint_parameter": "id" } ] } }
>>> requests.put(oep_url+'/api/v0/schema/sandbox/tables/example_table/', json=data, headers={'Authorization': 'Token %s'%your_token} )
<Response [201]>

If everything went right, you will receive a 201-Resonse and the table has been created.

Note

The OEP will automatically grant the ‘admin’-permissions on this table to your user.

>>> result = requests.get(oep_url+'/api/v0/schema/sandbox/tables/example_table/columns')
>>> result.status_code
200
>>> json_result = result.json()
>>> json_result['id'] == {'character_maximum_length': None, 'maximum_cardinality': None, 'is_nullable': False, 'data_type': 'bigint', 'numeric_precision': 64, 'character_octet_length': None, 'interval_type': None, 'dtd_identifier': '1', 'interval_precision': None, 'numeric_scale': 0, 'is_updatable': True, 'datetime_precision': None, 'ordinal_position': 1, 'column_default': "nextval('sandbox.example_table_id_seq'::regclass)", 'numeric_precision_radix': 2}
True
>>> json_result['geom'] == {'column_default': None, 'character_maximum_length': None, 'maximum_cardinality': None, 'is_nullable': True, 'data_type': 'USER-DEFINED', 'numeric_precision': None, 'character_octet_length': None, 'interval_type': None, 'dtd_identifier': '3', 'interval_precision': None, 'numeric_scale': None, 'is_updatable': True, 'datetime_precision': None, 'ordinal_position': 3, 'column_default': None, 'numeric_precision_radix': None}
True
>>> json_result['name'] == {'character_maximum_length': 50, 'maximum_cardinality': None, 'is_nullable': True, 'data_type': 'character varying', 'numeric_precision': None, 'character_octet_length': 200, 'interval_type': None, 'dtd_identifier': '2', 'interval_precision': None, 'numeric_scale': None, 'is_updatable': True, 'datetime_precision': None, 'ordinal_position': 2, 'column_default': None, 'numeric_precision_radix': None}
True

Note

A table must have a column ‘id’ of type ‘bigserial’.

>>> import requests
>>> data = { "query": { "columns": [ { "name":"name", "data_type": "varchar", "character_maximum_length": "50" }]} }
>>> response = requests.put(oep_url+'/api/v0/schema/sandbox/tables/faulty_table/', json=data, headers={'Authorization': 'Token %s'%your_token} )
>>> response.status_code
500
>>> response.json()['reason']
'Your table must have one column "id" of type "bigserial"'
>>> import requests
>>> data = { "query": { "columns": [ { "name":"id", "data_type": "integer"}]} }
>>> response = requests.put(oep_url+'/api/v0/schema/sandbox/tables/faulty_table/', json=data, headers={'Authorization': 'Token %s'%your_token} )
>>> response.status_code
500
>>> response.json()['reason']
'Your column "id" must have type "bigserial"'

Insert data

You can insert data into a specific table by sending a request to its /rows subresource. The query part of the sent data contians the row you want to insert in form of a JSON-dictionary::

{
    'name_of_column_1': 'value_in_column_1',
    'name_of_column_2': 'value_in_column_2',
    ...
}

If you the row you want to insert should have a specific id, send a PUT-request to the /rows/{id}/ subresource. In case the id should be generated automatically, just ommit the id field in the data dictionary and send a POST-request to the /rows/new subresource. If successful, the response will contain the id of the new row.

In the following example, we want to add a row containing just the name “John Doe”, but we do not want to set the the id of this entry.

curl:

curl
    -X POST
    -H "Content-Type: application/json"
    -H 'Authorization: Token <your-token>'
    -d '{"query": {"name": "John Doe"}}'
    oep.iks.cs.ovgu.de/api/v0/schema/sandbox/tables/example_table/rows/

python:

>>> import requests
>>> data = {"query": {"name": "John Doe"}}
>>> result = requests.post(oep_url+'/api/v0/schema/sandbox/tables/example_table/rows/new', json=data, headers={'Authorization': 'Token %s'%your_token} )
>>> result.status_code
201
>>> json_result = result.json()
>>> json_result['data'] # Show the id of the new row
[[1]]

Alternatively, we can specify that the new row should be stored under id 12:

python:

>>> import requests
>>> data = {"query": {"name": "Mary Doe XII"}}
>>> result = requests.put(oep_url+'/api/v0/schema/sandbox/tables/example_table/rows/12', json=data, headers={'Authorization': 'Token %s'%your_token} )
>>> result.status_code
201

Our database should have the following structure now:

id: int name: varchar(50) geom: geometry(Point)
1 John Doe NULL
12 Mary Doe XII NULL

Note

In order to insert new data, or perfom any other actions that alter the data state, you need the ‘write’-permission for the respective table. Permissions can be granted by a user with ‘admin’-permissions in the OEP web interface.

Select data

You can insert data into a specific table by sending a GET-request to its /rows subresource. No authorization is required to do so.

curl:

curl
    -X GET
    oep.iks.cs.ovgu.de/api/v0/schema/sandbox/tables/example_table/rows/

The data will be returned as list of JSON-dictionaries similar to the ones used when adding new rows:

[
    {
        "name": "John Doe",
        "geom": null,
        "id": 1
    }
]

python:

>>> result = requests.get(oep_url+'/api/v0/schema/sandbox/tables/example_table/rows/', )
>>> result.status_code
200
>>> json_result = result.json()
>>> json_result ==  [{'id': 1, 'name': 'John Doe', 'geom': None}, {'id': 12, 'name': 'Mary Doe XII', 'geom': None}]
True

There are also optional parameters for these GET-queries:

  • limit: Limit the number of returned rows

  • offset: Ignore the specified amount of rows

  • orderby: Name of a column to refer when ordering

  • column: Name of a column to include in the results. If not present, all

    columns are returned

  • where: Constraint fourmulated as VALUE+OPERATOR+VALUE with

    • VALUE: Constant or name of a column

    • OPERATOR: One of the following:

      • EQUALS or =,
      • GREATER or >,
      • LOWER or <,
      • NOTEQUAL or != or <>,
      • NOTGREATER or <=,
      • NOTLOWER or >=,
>>> result = requests.get(oep_url+"/api/v0/schema/sandbox/tables/example_table/rows/?where=name=John+Doe", )
>>> result.status_code
200
>>> json_result = result.json()
>>> json_result == [{'id': 1, 'name': 'John Doe', 'geom': None}]
True
>>> result = requests.get(oep_url+"/api/v0/schema/sandbox/tables/example_table/rows/1", )
>>> result.status_code
200
>>> json_result = result.json()
>>> json_result == {'id': 1, 'name': 'John Doe', 'geom': None}
True
>>> result = requests.get(oep_url+"/api/v0/schema/sandbox/tables/example_table/rows/?offset=1")
>>> result.status_code
200
>>> json_result = result.json()
>>> json_result == [{'id': 12, 'name': 'Mary Doe XII', 'geom': None}]
True
>>> result = requests.get(oep_url+"/api/v0/schema/sandbox/tables/example_table/rows/?column=name&column=id")
>>> result.status_code
200
>>> json_result = result.json()
>>> json_result == [{'id': 1, 'name': 'John Doe'},{'id': 12, 'name': 'Mary Doe XII'}]
True

Add columns table

>>> data = {'query':{'data_type': 'varchar', 'character_maximum_length': 30}}
>>> result = requests.put(oep_url+"/api/v0/schema/sandbox/tables/example_table/columns/first_name", json=data, headers={'Authorization': 'Token %s'%your_token})
>>> result.status_code
201
>>> result = requests.get(oep_url+"/api/v0/schema/sandbox/tables/example_table/columns/first_name")
>>> result.status_code
200
>>> result.json() == {'numeric_scale': None, 'numeric_precision_radix': None, 'is_updatable': True, 'maximum_cardinality': None, 'character_maximum_length': 30, 'character_octet_length': 120, 'ordinal_position': 4, 'is_nullable': True, 'interval_type': None, 'data_type': 'character varying', 'dtd_identifier': '4', 'column_default': None, 'datetime_precision': None, 'interval_precision': None, 'numeric_precision': None}
True

Alter data

Our current table looks as follows:

id: bigserial name: varchar(50) geom: geometry(Point) first_name: varchar(30)
1 John Doe NULL NULL
12 Mary Doe XII NULL NULL

Our next task is to distribute for and last name to the different columns:

>>> result = requests.get(oep_url+'/api/v0/schema/sandbox/tables/example_table/rows/') # Load the names via GET
>>> result.status_code
200
>>> for row in result.json():
...     first_name, last_name = str(row['name']).split(' ', 1) # Split the names at the first space
...     data = {'query': {'name': last_name, 'first_name': first_name}} # Build the data dictionary and post it to /rows/<id>
...     result = requests.post(oep_url+'/api/v0/schema/sandbox/tables/example_table/rows/{id}'.format(id=row['id']), json=data, headers={'Authorization': 'Token %s'%your_token})
...     result.status_code
200
200

Now, our table looks as follows:

id: int name: varchar(50) geom: geometry(Point) first_name: varchar(30)
1 Doe NULL John
12 Doe XII NULL Mary

Alter tables

Currently, rows are allowed that contain no first name. In order to prohibit such behaviour, we have to set column first_name to NOT NULL. Such ALTER TABLE commands can be executed by POST-ing a dictionary with the corresponding values to the column’s resource:

>>> data = {'query': {'is_nullable': False}}
>>> result = requests.post(oep_url+"/api/v0/schema/sandbox/tables/example_table/columns/first_name", json=data, headers={'Authorization': 'Token %s'%your_token} )
>>> result.status_code
200

We can check, whether your command worked by retrieving the corresponding resource:

>>> result = requests.get(oep_url+"/api/v0/schema/sandbox/tables/example_table/columns/first_name")
>>> result.status_code
200
>>> json_result = result.json()
>>> json_result['is_nullable']
False

After prohibiting null-values in the first name column, such rows can not be added anymore.

>>> import requests
>>> data = {"query": {"name": "McPaul"}}
>>> result = requests.post(oep_url+'/api/v0/schema/sandbox/tables/example_table/rows/new', json=data, headers={'Authorization': 'Token %s'%your_token} )
>>> result.status_code
500
>>> result.json()['reason']
'Action violates not-null constraint on first_name. Failing row was (McPaul)'

Delete rows

In order to delete rows, you need the ‘delete’-permission on the respective table. The permissions can be granted by an admin in the OEP web interface.

>>> import requests
>>> data = {"query": {"name": "McPaul"}}
>>> result = requests.delete(oep_url+'/api/v0/schema/sandbox/tables/example_table/rows/1', json=data, headers={'Authorization': 'Token %s'%your_token} )
>>> result.status_code
200
>>> result = requests.get(oep_url+'/api/v0/schema/sandbox/tables/example_table/rows/1')
>>> result.status_code
404

Delete tables

In order to delete rows, you need the ‘admin’-permission on the respective table. The permissions can be granted by an admin in the OEP web interface.

>>> import requests
>>> requests.delete(oep_url+'/api/v0/schema/sandbox/tables/example_table', headers={'Authorization': 'Token %s'%your_token} )
<Response [200]>
>>> requests.get(oep_url+'/api/v0/schema/sandbox/tables/example_table')
<Response [404]>

For more advanced commands read Advanced API features