Sorting embedded arrays

[Sam]

Hi all,

Sorting doesn't work correctly in the example below:

> db.foo.save({thread: [ { name: 'apple', timestamp: 1 }, { name: 'orange', timestamp: 5} ]})
> db.foo.save({thread: [ { name: 'banana', timestamp: 10 } ] })

The following sorts return records in the same order (don't know
if MongoDB is actually sorting).
> db.foo.find().sort({'thread.timestamp' : 1})
> db.foo.find().sort({'thread.timestamp' : -1})

Is sorting in embedded arrays not supported? Thanks.

Sam

[Eliot Horowitz]

There is currently a bug where sorting by fields in arrays doesn't
work without an index.
See this case: http://jira.mongodb.org/browse/SERVER-480 for more
notes and a discussion on the "correct" behavior.

> --
>
> You received this message because you are subscribed to the Google Groups "mongodb-user" group.
> To post to this group, send email to mongod...@googlegroups.com.
> To unsubscribe from this group, send email to mongodb-user...@googlegroups.com.
> For more options, visit this group at http://groups.google.com/group/mongodb-user?hl=en.
>
>
>

[Kfir Shay]

on the topic of sorting.

while these two queries return the correct sorted result set:
db.coll_name.find().sort( { created_at : -1 } ).limit(1)
db.coll_name.find().sort( { created_at : 1 } ).limit(1)

all these three queries return the same result set:
db.coll_name.find().sort( { created_at : 'ascending' } ).limit(1)
db.coll_name.find().sort( { created_at : 'descending' } ).limit(1)
db.coll_name.find().sort( { created_at : 'whatever' } ).limit(1)

[Eliot Horowitz]

the string there is ignored since its invalid.

[Kfir Shay]

oh, I thought '(ascending|descending)' was replacing -1|1

[Kfir Shay]

am I missing something what is wrong with the syntax?
db.coll_name.find().sort( { created_at : 'descending' } ).limit(1)
db.coll_name.find().sort( { created_at : 'ascending' } ).limit(1)

[Michael Dirolf]

you should use -1 and 1 to specify direction, the shell doesn't interpret "descending" and "ascending" iirc

[Kfir Shay]

ok yet when doing the same queries using the ruby driver on Solaris I
get a log message telling me the -1, 1 syntax has been deprecated

[Kyle Banker]

which version of the ruby driver are you using?  in the latest, this produces no warnings:

@collection.find().sort([ [created_at, 1] ]).limit(1).to_a

[Kfir Shay]

got the code from github

(git clone git://github.com/mongodb/mongo-ruby-driver.git)

[Michael Dirolf]

it's also different in the ruby driver - :ascending and :descending
should work there IIRC. your first example looked like the shell,
where 1 and -1 are the only options.

[Geir Magnusson Jr.]

why not make them consistent?

[Michael Dirolf]

As kyle points out, 1 and -1 work in the ruby driver as well. Since
ruby provides symbols, which are sort of a perfect fit here, I think
it makes sense to extend the API and let developers do it either way.
There's nothing like symbols in JS for the shell, so can't do it
there.

[Geir Magnusson Jr.]

there are strings...

Just wondering, as this led to a bit of confusion here - we thought it was part of standard things you could pass as values for sort direcion.

geir

[Michael Dirolf]

Yeah the sorting APIs are a bit inconsistent right now. It's
compounded by the fact that JS objects are ordered and Ruby hashes /
Python dicts aren't - so the API in Ruby and Python takes a list of
tuples while in JS it takes an object.

I guess that's probably the reason for the naming inconsistency -
since the Ruby driver is already doing some extra work to translate
the sort specifier we added in the :ascending thing as well.

I do think it's okay for the APIs to differ somewhat when it makes
sense to be idiomatic, though. Open to suggestions for how to improve
things.