$slice works in a different way compared to mongodb about mingo HOT 9 CLOSED

There is an issue with this implementation as well. It still doesn't behave as the original mongodb specification is.

For reference here are the tests for the $slice in mongodb jstests code.

from mingo.

Yes. The reason for reopening the issue. Updating with a fix and some test cases.

from mingo.

There is one more issue with $slice. It currently excludes all other fields from the document.
$slice should just affect the property that is being "sliced", and not interfere in any way with the exlusion or inclusion of other fields.

from mingo.

can you provide an example of this behaviour. MongoDB only includes the projected fields in the result.

from mingo.

Sure.

Example document:
{
Text: "MyText",
Array: [1,2,3]
}

Fetching this document with a fields expression of:
{
Array: { $slice: 1 }
}

should return
{
Text: "MyText",
Array: [1],
_id: <....>
}

Notice that the Text and _id field will be included.
Furthermore, you can mix $slice with field exclusion and inclusion without affecting them:

Ex.
{
Array: { $slice: 1 },
Text: 0
}

{
Array: { $slice: 1 }
Text: 1,
_id: 0
}

etc.

Current implementation of mingo returns only the Array field when $slice is used.

from mingo.

Thanks. I am a bit surprised. This looks like a special case in MongoDB. The other projection operator $elemMatch does not behave the same way.

from mingo.

That IS surprising. Didn't know about $elemMatch. I would have expected that it works the same as $slice.

from mingo.

anyway. I have a fix coming up.

from mingo.

issue resolve in release 0.3.3

from mingo.