Move $match in front of $group if condition is on group key

In case of views created on results of a $group, if the subsequent query is filtering on _id field then it should be possible to push that $match in front of $group transforming it into filter against whatever field is being grouped.

Example:

Vew definition:

[ {$group:{_id:"$city", ...}} ] 

Query on view:

{$match: {_id:{$in:["NY", "SF"]}}}

Pipeline transformation:

// from

[ {$group:{_id:"$city", ...}}, {$match: {_id:{$in:["NY", "SF"]}}} ] 

// to

[{$match: {city:{$in:["NY", "SF"]}}}, {$group:{_id:"$city", ...}} ]