1 

     2 .. _Getting Data:

     3 

     4 Getting Data

     5 ------------

     6 

     7 You might have spotted this in the explanations about the views, to

     8 get data, when not using a toplevel method, you will execute an RQL

     9 query over the request. For more details about RQL, head out to the

    10 `RQL chapter`

    11 

    12 Basic cases

    13 ```````````

    14 In a similiar way that you might be used to in SQL, to obtain data

    15 from the RQL backend, you will execute an RQL command and obtain a

    16 resultset ::

    17 

    18    rset = self.req.execute(rql_command)

    19 

    20 Then, you can use the data from the rset.

    21 

    22 XXX complete section with examples

    23 

    24 Use of the cache for RQL execution

    25 ``````````````````````````````````

    26 Let's say you want to get T which is in configuration C, this translates to ::

    27 

    28          self.req.execute('Any T WHERE T in_conf C, C eid "%s"' % entity.eid)

    29 

    30 But it can also be written in a syntax that will benefit from the use

    31 of a cache on the RQL server side. ::

    32 

    33           self.req.execute('Any T WHERE T in_conf C, C eid %(x)s', {'x': entity.eid}, 'x')

    34 

    35 The syntax tree is build once for the "generic" RQL and can be re-used

    36 with a number of different eid. Alternativelly, some of the common

    37 data related to an entity can be obtained from the top-level

    38 `entity.related()` method. The above would then be translated to ::

    39 

    40     entity.related('in_conf', 'object')

    41 

    42 The `related()` method makes extensive use of the cache mechanisms so

    43 you don't have to worry about them. Additionnaly this use will get you

    44 commonly used attributes that you will be able to use in your view

    45 generation without having to ask the data backend.

    46