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https://issues.apache.org/jira/browse/COUCHDB-1868?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13737127#comment-13737127
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Jan Lehnardt commented on COUCHDB-1868:
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[~dedalo] I totally get why returning null rows is a nice convenience :)
My reasoning is this:
1. _all_docs should behave like regular views if at all possible.
2. Regular views do not send empty rows when requested with multiple keys (in
fact, in terms of ranges, that can be an unbounded result, so we need to be
careful here that this only applies to POST {keys:[...]} and maybe other
caveats)
3. I haven’t looked at the code, but I assume the easiest thing to do is remove
the null-rows code from _all_docs, rather than adding sending null-rows to
regular views. Hence, the minimum thing we should do to achieve behaviour
parity is remove null-rows from all docs (or make it optional with a query
parameter).
4. If anyone feels like sitting down allowing both _all_docs and regular views
to have null-rows off by default and on-by-query-parameter, that is what I
think we should go for, but I am happy to get parity by sacrificing null-rows
on just _all_docs as a first step.
> Using multiple keys, the _all_docs built-in view acts differently then a user
> defined view
> ------------------------------------------------------------------------------------------
>
> Key: COUCHDB-1868
> URL: https://issues.apache.org/jira/browse/COUCHDB-1868
> Project: CouchDB
> Issue Type: Bug
> Components: View Server Support
> Reporter: Filippo Fadda
>
> When you query a view using multiple keys, the _all_docs built-in view acts
> differently then a user defined view:
> 1) in the first case CouchDB returns "not_found" for every not found key;
> 2) querying a user defined view produces, instead, an empty array.
> In the first case you obtain error="not_found" for every key, when you query
> a user defined view you simply don't get any rows, just the total rows for
> the view.
> See: http://pastebin.com/D7NExJrd
> Now, regarding 'keys' the documentation says something like: "Used to
> retrieve just the view rows matching that set of keys. Rows are returned in
> the order of the specified keys."
> In a normal case, CouchDB should return just a row for each matched key, but
> it will really help, having an option to return a row for every key, even
> there if not found, because it's more easy, cycle through results.
> Let's suppose the application I'm doing gets the last 30 blog posts,
> displaying for each one, information that are stored into related documents.
> The application will query, using as keys the posts' identifiers, other views
> to get, for example, if a post has been starred from the current logged-in
> user, etc.
> If a view always returns a number of rows equals to the number of keys, the
> application can cycle from 0 to 29 and display all the related information
> for a post.
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