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From David Zülke (JIRA) <j...@apache.org>
Subject [jira] [Created] (COUCHDB-1188) View query option defaults
Date Mon, 06 Jun 2011 14:46:59 GMT
View query option defaults
--------------------------

                 Key: COUCHDB-1188
                 URL: https://issues.apache.org/jira/browse/COUCHDB-1188
             Project: CouchDB
          Issue Type: New Feature
          Components: JavaScript View Server
    Affects Versions: 1.0.2
            Reporter: David Zülke
            Priority: Minor
             Fix For: 1.1.1


Currently, it's necessary to have intimate-ish knowledge of the inner workings of a view when
calling it, e.g.:

http://localhost:5984/mydb/_design/burp/_view/count-laser-beams?group_level=2

If the group level was different, the results returned by the view might be useless.

Other good examples are "include_docs", "inclusive_end" or "descending". For instance, views
that pull in foreign documents by emitting {_id: ...} as a value will only produce useful
results when called with "include_docs" set to true.

I'd suggest a feature where inside a view definition, a new key "query_defaults" alongside
"map" or "reduce" contains a hash map of query option keys and values that will be used when
calling the view unless one of the pre-defined options is passed as a query argument, in which
case the explicitly given query argument would take precedence.

Example:

"views": {
   "talks-by-room": {
       "map": "function(doc) {\n\tif(doc.type == 'talk' && doc.date_start) {\n\t\temit([doc.room,
doc.date_start, 0], doc.name);\n\t\tif(doc.speaker) {\n\t\t\temit([doc.room, doc.date_start,
1], {_id: doc.speaker});\n\t\t}\n\t}\n};",
       "query_defaults": {
           "include_docs": true
       }
   }
}

http://localhost:5984/couchcamp/_design/burp/_view/talks-by-room would be run with include_docs=true,
but the doc inclusion could be suppressed by requesting http://localhost:5984/couchcamp/_design/burp/_view/talks-by-room?include_docs=false

Alternative names for the new key are "query_options" or "query_option_defaults". Whilst I
prefer "query_options", I think "query_defaults" will be the better choice as it underlines
the nature of the functionality - namely, that the options defined therein may be overridden
by the caller.

Someone on the dev list suggested to use _rewrite, but the idea is that the defaults also
apply when invoking a list function. So you'd need two rewrites, one for the view if you want
to call it standalone, and one for the list function. And then you'd still have the issue
that the behavior of the view is changed by the rewrite, which is confusing to anyone looking
at the view code - you have to look at the rewrite as well to get the whole picture. Not good.

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