Thanks for the pointer. This seems a little bit different to me, as the
fetched document is an older version that wouldn't match the view in the first
place. There is no change to the document after it matches the view.
If I have a document:
{
"_id": "1234"
"_rev": 1-
"match": false
}
And a view defined as:
if(doc.match) {
emit();
}
Revision 1 of the document does not match the view.
If I write:
{
"_id": "1234"
"_rev": 2-
"match": true
}
At about the same time (within a few ms) as I query the view, I get a return
showing the document now matches, however the included "doc": {} is "_rev": 1-
There are no additional changes made to the document, and if I add a few more
ms between the write, and the query the included document is correctly "_rev":
2-
Either way it sounds like calling the view without include_docs, then retriving
using the _all_docs with a keys = [] is a better way to go?
-----Original Message-----
From: Robert Newson [mailto:[email protected]]
Sent: 2013, October, 31 9:39 AM
To: [email protected]
Subject: Re: Views with include_docs=true including old or incomplete results.
https://wiki.apache.org/couchdb/HTTP_view_API
The include_docs option will include the associated document. However, the user
should keep in mind that there is a race condition when using this option. It
is possible that between reading the view data and fetching the corresponding
document that the document has changed. If you want to alleviate such concerns
you should emit an object with a _rev attribute as in emit(key, {"_rev":
doc._rev}). This alleviates the race condition but leaves the possibility that
the returned document has been deleted (in which case, it includes the
"_deleted":
true attribute). Note: include_docs will cause a single document lookup per
returned view result row. This adds significant strain on the storage system if
you are under high load or return a lot of rows per request. If you are
concerned about this, you can emit the full doc in each row; this will increase
view index time and space requirements, but will make view reads optimally fast.
B.
On 31 October 2013 13:09, Mclean, Adam <[email protected]> wrote:
> I have a busy database that I'm querying with a view like
> "_design/[doc]/_view/[view]?include_docs=true"
>
> I'm having trouble with old or incomplete documents being included in the
> result.
>
> I see that either:
> a) include_docs is including the previous version of the document - a version
> of the document that wouldn't actually match the view.
> b) include_docs is not including the document. It includes the 'key', and
> 'value', but the 'doc' is empty in output.
>
> This only occurs if I'm querying the view at roughly the same time (within a
> few ms) of the incorrectly included document being written. The document
> being written/updated DOES match the view criteria, however the include_docs
> seems to have a timing issue where it retrieves an old copy of the document,
> or doesn't include anything in the "doc": {} portion of the result.
>
> So in summary I think the view logic is fine, but include_docs seems to
> retrieve incorrect documents when the timing lines up.
>
> I'm using CouchDB 1.3.1 with ERL R15B02 and Spidermonkey 1.8.5 on Linux.
>
> Is this a caveat of using include_docs? Would I be smarter to get the keys,
> then make a second query to couch to get the documents? Was this something
> 'known' in 1.3.1 and fixed in 1.4?
>
> Thanks!
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