Using limit=0 and details=on to get only the count of elements

[fgalan]

(Feedback from ECFI 2015 at Hamburg)

Currenetly limit=0 returns an error:

fermin@neodeb:~/ecfi$ curl --header 'Accept: application/json' --header 'Fiware-service: devguide' 'localhost:1026/v1/contextEntities?limit=0&details=on'
{
  "orionError" : {
    "code" : "400",
    "reasonPhrase" : "Bad Request",
    "details" : "Bad pagination limit: /0/ [a value of ZERO is unacceptable]"
  }
}

However, ?limit=0&details=on has been suggested as a way of getting only the count for entities.

The "projection" of this idea in NGSIv2 could be taken into account.

[jmcanterafonseca]

in NGSIv2 we have options=count . so if we say limit=0&options=count then yes it should be a valid operation and return success

[fgalan]

We should suppport:

GET /v2/entities?limit=0&options=count

200 OK
Fiware-total-count: 2321
[]

and also this one (useless, but semantically correct):

GET /v2/entities?limit=0

200 OK
[]

[fgalan]

Out of the scope of NGSIv2, althouth it is a good idea that could (potentially) be included in a later version of the API (v2.1) in a backward compatible way.

CC: @jmcanterafonseca

[Anjali-NEC]

Hi @fgalan Sir,

I would like to work on this issue. please let me know if this issue still need to be fix?

[fgalan]

Thanks for your willingness to work on this issue!

As far as I understand, the issue is still valid. This comment contains and specification of what needs to be implemented: #1492 (comment)

[Anjali-NEC]

I have fixed this issue. Please review my PR #3994 if it is ok then please merge it into master.

[fgalan]

I have fixed this issue. Please review my PR #3994 if it is ok then please merge it into master.

Merged in prelanding branch, the work continues in PR #4104