Query-like aggregation

[njoyard]

As a followup to #1400, here is my take on more Query-like features for aggregation.

I added an Aggregate constructor with chainable methods; an Aggregate is created when calling Model.aggregate (but the previous syntax still works).

// Previous syntax
Model.aggregate(
  { $group: { _id: null, maxAge: { $max: '$age' } } }
, { $project: { _id: 0, maxAge: 1 } }
, function (err, docs) { ... });

// New syntax
Model.aggregate() // instanceof Aggregate
  .group({ _id: null, maxAge: { $max: '$age' } })
  .select("-_id maxAge") // or  .project({ _id: 0, maxAge: 1 })
  .exec(function (err, docs) { ... }) // instanceof Promise

// Arbitrary operators
Model.aggregate()
  .append(
    { $group: { _id: null, maxAge: { $max: '$age' } } }
  , { $project: { _id: 0, maxAge: 1 } }
  ).exec(callback);

I created methods for each existing operator: group, project (with a Query-like select alternative), skip, limit, geoNear, group, unwind, match and sort.

Everything has jsdoc and tests (in model.aggregate.test.js and aggregate.test.js) that all pass as of my last commit (njoyard@19ce303).

Things that might be useful to add:

• Query-like where/in/lt/gt/... methods to create $match operators. Would be nice to find a way to reuse Query code without actually duplicating it.
• Casting aggregated docs to a matching Schema

Thanks for your feedback !

[aheckmann]

Sounds good. Will review next week.

On Thu, Mar 28, 2013 at 2:13 AM, Nicolas Joyard notifications@git.luolix.topwrote:

Here is my take on more Query-like features for aggregation.

I added an Aggregate constructor with chainable methods; an Aggregate is
created when calling Model.aggregate (but the previous syntax still works).

// Previous syntaxModel.aggregate(
{ $group: { _id: null, maxAge: { $max: '$age' } } }, { $project: { _id: 0, maxAge: 1 } }, function (err, docs) { ... });
// New syntaxModel.aggregate() // instanceof Aggregate
.group({ _id: null, maxAge: { $max: '$age' } })
.select("-_id maxAge") // or .project({ _id: 0, maxAge: 1 })
.exec(function (err, docs) { ... }) // instanceof Promise
// Arbitrary operatorsModel.aggregate()
.append(
{ $group: { _id: null, maxAge: { $max: '$age' } } }
, { $project: { _id: 0, maxAge: 1 } }
).exec(callback);

I created methods for each existing operator: group, project (with a
query-like select alternative), skip, limit, geoNear, group, unwind, match
and sort.

Everything has jsdoc and tests (in model.aggregate.test.js and
aggregate.test.js) that all pass as of my last commit (njoyard/mongoose@19ce303njoyard@19ce303
).

Things that might be useful to add:

• Query-like where/in/lt/gt/... methods to create $match operators.
  Would be nice to find a way to reuse Query code without actually
  duplicating it.
• Casting aggregated docs to a matching Schema

Thanks for your feedback !

You can merge this Pull Request by running

git pull https://github.com/njoyard/mongoose master

Or view, comment on, or merge it at:

#1404
Commit Summary

• Basic Aggregate implementation
• Added jsdoc to Aggregate
• Rename #cast to #bind, more descriptive of what it actually does
• Added #unwind #sort and #match
• Merge identical methods
• Add links to doc, add missing tests
• Fix minor doc issues
• Plug Aggregate into Model.aggregate()
• More Model.aggregate() tests

File Changes

• A lib/aggregate.jshttps://github.com/Query-like aggregation #1404/files#diff-0(368)
• M lib/model.jshttps://github.com/Query-like aggregation #1404/files#diff-1(49)
• A test/aggregate.test.jshttps://github.com/Query-like aggregation #1404/files#diff-2(477)
• M test/model.aggregate.test.jshttps://github.com/Query-like aggregation #1404/files#diff-3(28)

Patch Links:

• https://github.com/LearnBoost/mongoose/pull/1404.patch
• https://github.com/LearnBoost/mongoose/pull/1404.diff

Aaron
@aaronheckmann https://twitter.com/#!/aaronheckmann

[aheckmann]

merged for 3.7. Thanks!