mquery

mquery is a fluent mongodb query builder designed to run in multiple environments.



Features

- fluent query builder api
- custom base query support
- MongoDB 2.4 geoJSON support
- method + option combinations validation
- node.js driver compatibility
- environment detection
- debug support
- separated collection implementations for maximum flexibility

Use

``js
const mongo = require('mongodb');

const client = new mongo.MongoClient(uri);
await client.connect();
// get a collection
const collection = client.collection('artists');

// pass it to the constructor
await mquery(collection).find({...});

// or pass it to the collection method
const docs = await mquery().find({...}).collection(collection);

// or better yet, create a custom query constructor that has it always set
const Artist = mquery(collection).toConstructor();
const docs = await Artist().find(...).where(...);
`

mquery requires a collection object to work with. In the example above we just pass the collection object created using the official MongoDB driver.

Fluent API

- mquery
- Features
- Use
- Fluent API
- Helpers
- find()
- findOne()
- countDocuments()
- estimatedDocumentCount()
- findOneAndUpdate()
- findOneAndUpdate() options
- findOneAndReplace()
- findOneAndReplace() options
- findOneAndRemove()
- findOneAndRemove() options
- distinct()
- updateMany()
- updateOne()
- replaceOne()
- deleteOne()
- deleteMany()
- exec()
- cursor()
- stream()
- all()
- and()
- box()
- circle()
- elemMatch()
- equals()
- eq()
- exists()
- geometry()
- gt()
- gte()
- in()
- intersects()
- lt()
- lte()
- maxDistance()
- mod()
- ne()
- nin()
- nor()
- near()
- Example
- or()
- polygon()
- regex()
- select()
- String syntax
- selected()
- selectedInclusively()
- selectedExclusively()
- size()
- slice()
- within()
- where()
- $where()
- batchSize()
- collation()
- comment()
- hint()
- j()
- limit()
- maxTime()
- skip()
- sort()
- read()
- Preferences:
- Preference Tags:
- readConcern()
- Read Concern Level:
- writeConcern()
- Write Concern:
- slaveOk()
- tailable()
- wtimeout()
- Helpers
- collection()
- then()
- merge(object)
- setOptions(options)
- setOptions() options
- setTraceFunction(func)
- mquery.setGlobalTraceFunction(func)
- mquery.canMerge(conditions)
- mquery.use$geoWithin
- Custom Base Queries
- Validation
- Debug support
- General compatibility
- ObjectIds
- Read Preferences
- Future goals
- Installation
- License

Helpers

- collection
- then
- merge
- setOptions
- setTraceFunction
- mquery.setGlobalTraceFunction
- mquery.canMerge
- mquery.use$geoWithin

$3

Declares this query a _find_ query. Optionally pass a match clause.

`js
mquery().find()
mquery().find(match)
await mquery().find()
const docs = await mquery().find(match);
assert(Array.isArray(docs));
`

$3

Declares this query a _findOne_ query. Optionally pass a match clause.

`js
mquery().findOne()
mquery().findOne(match)
await mquery().findOne()
const doc = await mquery().findOne(match);
if (doc) {
// the document may not be found
console.log(doc);
}
`

$3

Declares this query a _countDocuments_ query. Optionally pass a match clause.

`js
mquery().countDocuments()
mquery().countDocuments(match)
await mquery().countDocuments()
const number = await mquery().countDocuments(match);
console.log('we found %d matching documents', number);
`

$3

Declares this query an _estimatedDocumentCount_ query. Gets an estimated count of documents in a collection using collection metadata.

`js
mquery().estimatedDocumentCount()
const number = await mquery().estimatedDocumentCount();
console.log('estimated documents: %d', number);
`

$3

Declares this query a _findAndModify_ with update query. Optionally pass a match clause, update document, options.

When executed, the first matching document (if found) is modified according to the update document and passed back.

#### findOneAndUpdate() options

Options are passed to the setOptions() method.

- new: boolean - true to return the modified document rather than the original. defaults to false
- upsert: boolean - creates the object if it doesn't exist. defaults to false
- sort: if multiple docs are found by the match condition, sets the sort order to choose which doc to update

`js
query.findOneAndUpdate()
query.findOneAndUpdate(updateDocument)
query.findOneAndUpdate(match, updateDocument)
query.findOneAndUpdate(match, updateDocument, options)

// the following all execute the command
await query.findOneAndUpdate()
await query.findOneAndUpdate(updateDocument)
await query.findOneAndUpdate(match, updateDocument)
const doc = await query.findOneAndUpdate(match, updateDocument, options);
if (doc) {
// the document may not be found
console.log(doc);
}
`

$3

Declares this query a _findOneAndReplace_ query. Finds a matching document, replaces it with the provided replacement, and returns the found document (if any).

#### findOneAndReplace() options

Options are passed to the setOptions() method.

- new: boolean - true to return the modified document rather than the original. defaults to false
- upsert: boolean - creates the object if it doesn't exist. defaults to false
- sort: if multiple docs are found by the match condition, sets the sort order to choose which doc to replace

`js
query.findOneAndReplace()
query.findOneAndReplace(replacement)
query.findOneAndReplace(match, replacement)
query.findOneAndReplace(match, replacement, options)

// the following all execute the command
await query.findOneAndReplace()
await query.findOneAndReplace(replacement)
await query.findOneAndReplace(match, replacement)
const doc = await query.findOneAndReplace(match, replacement, options);
if (doc) {
// the document may not be found
console.log(doc);
}
`

$3

Declares this query a _findAndModify_ with remove query. Alias of findOneAndDelete.
Optionally pass a match clause, options.

When executed, the first matching document (if found) is modified according to the update document, removed from the collection and passed as a result.

#### findOneAndRemove() options

Options are passed to the setOptions() method.

- sort: if multiple docs are found by the condition, sets the sort order to choose which doc to modify and remove

`js
A.where().findOneAndDelete()
A.where().findOneAndRemove()
A.where().findOneAndRemove(match)
A.where().findOneAndRemove(match, options)

// the following all execute the command
await A.where().findOneAndRemove()
await A.where().findOneAndRemove(match)
const doc = await A.where().findOneAndRemove(match, options);
if (doc) {
// the document may not be found
console.log(doc);
}
`

$3

Declares this query a _distinct_ query. Optionally pass the distinct field, a match clause.

`js
mquery().distinct()
mquery().distinct(match)
mquery().distinct(match, field)
mquery().distinct(field)

// the following all execute the command
await mquery().distinct()
await mquery().distinct(field)
await mquery().distinct(match)
const result = await mquery().distinct(match, field);
console.log(result);
`

$3

Declares this query an _updateMany_ query. Updates all documents that match criteria.

When executed, the first argument is the query, and the second argument is the update document.

_All paths passed that are not $atomic operations will become $set ops._

`js
mquery().updateMany({ name: /^match/ }, { field: 'value' })
await mquery().updateMany({ name: /^match/ }, { field: 'value' })
await mquery().where({ name: /^match/ }).updateMany({ field: 'value' })
`

$3

Declares this query an _updateOne_ query. Updates only the first document that matches criteria.

When executed, the first argument is the query, and the second argument is the update document.

_All paths passed that are not $atomic operations will become $set ops._

`js
mquery().updateOne({ name: 'match' }, { field: 'value' })
await mquery().updateOne({ name: 'match' }, { field: 'value' })
await mquery().where({ name: 'match' }).updateOne({ field: 'value' })
`

$3

Declares this query a _replaceOne_ query. Replaces the first document that matches criteria with the provided replacement document.

Similar to updateOne(), except replaceOne() is not allowed to use atomic modifiers ($set, $push, etc.). Calling replaceOne() will always replace the existing doc.

`js
mquery().replaceOne({ _id: 1 }, { name: 'new name', age: 25 })
await mquery().replaceOne({ _id: 1 }, { name: 'new name', age: 25 })
`

$3

Declares this query a _deleteOne_ query. Deletes the first document that matches criteria.

`js
mquery().deleteOne({ name: 'match' })
await mquery().deleteOne({ name: 'match' })
await mquery().where({ name: 'match' }).deleteOne()
`

$3

Declares this query a _deleteMany_ query. Deletes all documents that match criteria.

`js
mquery().deleteMany({ name: /^match/ })
await mquery().deleteMany({ name: /^match/ })
await mquery().where({ name: /^match/ }).deleteMany()
`

$3

Executes the query.

`js
const docs = await mquery().findOne().where('route').intersects(polygon).exec()
`

$3

Returns a cursor for the given find query.

`js
const cursor = mquery().find({ name: /^match/ }).cursor();
cursor.on('data', function(doc) {
console.log(doc);
});
cursor.on('end', function() {
console.log('done');
});
`

Note: this only works with find() operations.

$3

Executes the query and returns a stream.

`js
var stream = mquery().find().stream(options);
stream.on('data', cb);
stream.on('close', fn);
`

Note: this only works with find() operations.

Note: returns the stream object directly from the node-mongodb-native driver. (currently streams1 type stream). Any options will be passed along to the driver method.

---

$3

Specifies an $all query condition

`js
mquery().where('permission').all(['read', 'write'])
`

MongoDB documentation

$3

Specifies arguments for an $and condition

`js
mquery().and([{ color: 'green' }, { status: 'ok' }])
`

MongoDB documentation

$3

Specifies a $box condition

`js
var lowerLeft = [40.73083, -73.99756]
var upperRight= [40.741404, -73.988135]

mquery().where('location').within().box(lowerLeft, upperRight)
`

MongoDB Documentation

$3

Specifies a $center or $centerSphere condition.

`js
var area = { center: [50, 50], radius: 10, unique: true }
query.where('loc').within().circle(area)
query.circle('loc', area);

// for spherical calculations
var area = { center: [50, 50], radius: 10, unique: true, spherical: true }
query.where('loc').within().circle(area)
query.circle('loc', area);
`

- MongoDB Documentation - center
- MongoDB Documentation - centerSphere

$3

Specifies an $elemMatch condition

`js
query.where('comment').elemMatch({ author: 'autobot', votes: {$gte: 5}})

query.elemMatch('comment', function (elem) {
elem.where('author').equals('autobot');
elem.where('votes').gte(5);
})
`

MongoDB Documentation

$3

Specifies the complementary comparison value for the path specified with where().

`js
mquery().where('age').equals(49);

// is the same as

mquery().where({ 'age': 49 });
`

$3

Alias of equals(). Specifies the complementary comparison value for the path specified with where().

`js
mquery().where('age').eq(49);

// is the same as

mquery().where('age').equals(49);

// is the same as

mquery().where({ 'age': 49 });
`

$3

Specifies an $exists condition

`js
// { name: { $exists: true }}
mquery().where('name').exists()
mquery().where('name').exists(true)
mquery().exists('name')

// { name: { $exists: false }}
mquery().where('name').exists(false);
mquery().exists('name', false);
`

MongoDB Documentation

$3

Specifies a $geometry condition

`js
var polyA = [[[ 10, 20 ], [ 10, 40 ], [ 30, 40 ], [ 30, 20 ]]]
query.where('loc').within().geometry({ type: 'Polygon', coordinates: polyA })

// or
var polyB = [[ 0, 0 ], [ 1, 1 ]]
query.where('loc').within().geometry({ type: 'LineString', coordinates: polyB })

// or
var polyC = [ 0, 0 ]
query.where('loc').within().geometry({ type: 'Point', coordinates: polyC })

// or
query.where('loc').intersects().geometry({ type: 'Point', coordinates: polyC })

// or
query.where('loc').near().geometry({ type: 'Point', coordinates: [3,5] })
`

geometry() must come after intersects(), within(), or near().

The object argument must contain type and coordinates properties.

- type String
- coordinates Array

MongoDB Documentation

$3

Specifies a $gt query condition.

`js
mquery().where('clicks').gt(999)
`

MongoDB Documentation

$3

Specifies a $gte query condition.

MongoDB Documentation

`js
mquery().where('clicks').gte(1000)
`

$3

Specifies an $in query condition.

`js
mquery().where('author_id').in([3, 48901, 761])
`

MongoDB Documentation

$3

Declares an $geoIntersects query for geometry().

`js
query.where('path').intersects().geometry({
type: 'LineString'
, coordinates: [[180.0, 11.0], [180, 9.0]]
})

// geometry arguments are supported
query.where('path').intersects({
type: 'LineString'
, coordinates: [[180.0, 11.0], [180, 9.0]]
})
`

Must be used after where().

MongoDB Documentation

$3

Specifies a $lt query condition.

`js
mquery().where('clicks').lt(50)
`

MongoDB Documentation

$3

Specifies a $lte query condition.

`js
mquery().where('clicks').lte(49)
`

MongoDB Documentation

$3

Specifies a $maxDistance query condition.

`js
mquery().where('location').near({ center: [139, 74.3] }).maxDistance(5)
`

MongoDB Documentation

$3

Specifies a $mod condition

`js
mquery().where('count').mod(2, 0)
`

MongoDB Documentation

$3

Specifies a $ne query condition.

`js
mquery().where('status').ne('ok')
`

MongoDB Documentation

$3

Specifies an $nin query condition.

`js
mquery().where('author_id').nin([3, 48901, 761])
`

MongoDB Documentation

$3

Specifies arguments for an $nor condition.

`js
mquery().nor([{ color: 'green' }, { status: 'ok' }])
`

MongoDB Documentation

$3

Specifies arguments for a $near or $nearSphere condition.

These operators return documents sorted by distance.

#### Example

`js
query.where('loc').near({ center: [10, 10] });
query.where('loc').near({ center: [10, 10], maxDistance: 5 });
query.near('loc', { center: [10, 10], maxDistance: 5 });

// GeoJSON
query.where('loc').near({ center: { type: 'Point', coordinates: [10, 10] }});
query.where('loc').near({ center: { type: 'Point', coordinates: [10, 10] }, maxDistance: 5, spherical: true });
query.where('loc').near().geometry({ type: 'Point', coordinates: [10, 10] });

// For a $nearSphere condition, pass the spherical option.
query.near({ center: [10, 10], maxDistance: 5, spherical: true });
`

MongoDB Documentation

$3

Specifies arguments for an $or condition.

`js
mquery().or([{ color: 'red' }, { status: 'emergency' }])
`

MongoDB Documentation

$3

Specifies a $polygon condition

`js
mquery().where('loc').within().polygon([10,20], [13, 25], [7,15])
mquery().polygon('loc', [10,20], [13, 25], [7,15])
`

MongoDB Documentation

$3

Specifies a $regex query condition.

`js
mquery().where('name').regex(/^sixstepsrecords/)
`

MongoDB Documentation

$3

Specifies which document fields to include or exclude

`js
// 1 means include, 0 means exclude
mquery().select({ name: 1, address: 1, _id: 0 })

// or

mquery().select('name address -_id')
`

#### String syntax

When passing a string, prefixing a path with - will flag that path as excluded. When a path does not have the - prefix, it is included.

`js
// include a and b, exclude c
query.select('a b -c');

// or you may use object notation, useful when
// you have keys already prefixed with a "-"
query.select({a: 1, b: 1, c: 0});
`

_Cannot be used with distinct()._

$3

Determines if the query has selected any fields.

`js
var query = mquery();
query.selected() // false
query.select('-name');
query.selected() // true
`

$3

Determines if the query has selected any fields inclusively.

`js
var query = mquery().select('name');
query.selectedInclusively() // true

var query = mquery();
query.selected() // false
query.select('-name');
query.selectedInclusively() // false
query.selectedExclusively() // true
`

$3

Determines if the query has selected any fields exclusively.

`js
var query = mquery().select('-name');
query.selectedExclusively() // true

var query = mquery();
query.selected() // false
query.select('name');
query.selectedExclusively() // false
query.selectedInclusively() // true
`

$3

Specifies a $size query condition.

`js
mquery().where('someArray').size(6)
`

MongoDB Documentation

$3

Specifies a $slice projection for a path

`js
mquery().where('comments').slice(5)
mquery().where('comments').slice(-5)
mquery().where('comments').slice([-10, 5])
`

MongoDB Documentation

$3

Sets a $geoWithin or $within argument for geo-spatial queries.

`js
mquery().within().box()
mquery().within().circle()
mquery().within().geometry()

mquery().where('loc').within({ center: [50,50], radius: 10, unique: true, spherical: true });
mquery().where('loc').within({ box: [[40.73, -73.9], [40.7, -73.988]] });
mquery().where('loc').within({ polygon: [[],[],[],[]] });

mquery().where('loc').within([], [], []) // polygon
mquery().where('loc').within([], []) // box
mquery().where('loc').within({ type: 'LineString', coordinates: [...] }); // geometry
`

As of mquery 2.0, $geoWithin is used by default. This impacts you if running MongoDB < 2.4. To alter this behavior, see mquery.use$geoWithin.

Must be used after where().

MongoDB Documentation

$3

Specifies a path for use with chaining

`js
// instead of writing:
mquery().find({age: {$gte: 21, $lte: 65}});

// we can instead write:
mquery().where('age').gte(21).lte(65);

// passing query conditions is permitted too
mquery().find().where({ name: 'vonderful' })

// chaining
await mquery()
.where('age').gte(21).lte(65)
.where({ 'name': /^vonderful/i })
.where('friends').slice(10)
.exec()
`

$3

Specifies a $where condition.

Use $where when you need to select documents using a JavaScript expression.

`js
await query.$where('this.comments.length > 10 || this.name.length > 5').exec()

query.$where(function () {
return this.comments.length > 10 || this.name.length > 5;
})
`

Only use $where when you have a condition that cannot be met using other MongoDB operators like $lt. Be sure to read about all of its caveats before using.

---

$3

Specifies the batchSize option.

`js
query.batchSize(100)
`

_Cannot be used with distinct()._

MongoDB documentation

$3

Specifies the collation option.

`js
query.collation({ locale: "en_US", strength: 1 })
`

MongoDB documentation

$3

Specifies the comment option.

`js
query.comment('login query');
`

_Cannot be used with distinct()._

MongoDB documentation

$3

Sets query hints.

`js
mquery().hint({ indexA: 1, indexB: -1 })
`

_Cannot be used with distinct()._

MongoDB documentation

$3

Requests acknowledgement that this operation has been persisted to MongoDB's on-disk journal.

This option is only valid for operations that write to the database:

- deleteOne()
- deleteMany()
- findOneAndDelete()
- findOneAndUpdate()
- updateOne()
- updateMany()

Defaults to the j value if it is specified in writeConcern

`js
mquery().j(true);
`

$3

Specifies the limit option.

`js
query.limit(20)
`

_Cannot be used with distinct()._

MongoDB documentation

$3

Specifies the maxTimeMS option.

`js
query.maxTime(100)
query.maxTimeMS(100)
`

MongoDB documentation

$3

Specifies the skip option.

`js
query.skip(100).limit(20)
`

_Cannot be used with distinct()._

MongoDB documentation

$3

Sets the query sort order.

If an object is passed, key values allowed are asc, desc, ascending, descending, 1, and -1.

If a string is passed, it must be a space delimited list of path names. The sort order of each path is ascending unless the path name is prefixed with - which will be treated as descending.

`js
// these are equivalent
query.sort({ field: 'asc', test: -1 });
query.sort('field -test');
`

_Cannot be used with distinct()._

MongoDB documentation

$3

Sets the readPreference option for the query.

`js
mquery().read('primary')
mquery().read('p') // same as primary

mquery().read('primaryPreferred')
mquery().read('pp') // same as primaryPreferred

mquery().read('secondary')
mquery().read('s') // same as secondary

mquery().read('secondaryPreferred')
mquery().read('sp') // same as secondaryPreferred

mquery().read('nearest')
mquery().read('n') // same as nearest

mquery().setReadPreference('primary') // alias of .read()
`

#### Preferences:

- primary - (default) Read from primary only. Operations will produce an error if primary is unavailable. Cannot be combined with tags.
- secondary - Read from secondary if available, otherwise error.
- primaryPreferred - Read from primary if available, otherwise a secondary.
- secondaryPreferred - Read from a secondary if available, otherwise read from the primary.
- nearest - All operations read from among the nearest candidates, but unlike other modes, this option will include both the primary and all secondaries in the random selection.

Aliases

- p primary
- pp primaryPreferred
- s secondary
- sp secondaryPreferred
- n nearest

#### Preference Tags:

To keep the separation of concerns between mquery and your driver
clean, mquery#read() no longer handles specifying a second tags argument as of version 0.5.
If you need to specify tags, pass any non-string argument as the first argument.
mquery will pass this argument untouched to your collections methods later.
For example:

`js
// example of specifying tags using the Node.js driver
var ReadPref = require('mongodb').ReadPreference;
var preference = new ReadPref('secondary', [{ dc:'sf', s: 1 },{ dc:'ma', s: 2 }]);
mquery(...).read(preference).exec();
`

Read more about how to use read preferences here and here.

$3

Sets the readConcern option for the query.

`js
// local
mquery().readConcern('local')
mquery().readConcern('l')
mquery().r('l')

// available
mquery().readConcern('available')
mquery().readConcern('a')
mquery().r('a')

// majority
mquery().readConcern('majority')
mquery().readConcern('m')
mquery().r('m')

// linearizable
mquery().readConcern('linearizable')
mquery().readConcern('lz')
mquery().r('lz')

// snapshot
mquery().readConcern('snapshot')
mquery().readConcern('s')
mquery().r('s')
`

#### Read Concern Level:

- local - The query returns from the instance with no guarantee guarantee that the data has been written to a majority of the replica set members (i.e. may be rolled back). (MongoDB 3.2+)
- available - The query returns from the instance with no guarantee guarantee that the data has been written to a majority of the replica set members (i.e. may be rolled back). (MongoDB 3.6+)
- majority - The query returns the data that has been acknowledged by a majority of the replica set members. The documents returned by the read operation are durable, even in the event of failure. (MongoDB 3.2+)
- linearizable - The query returns data that reflects all successful majority-acknowledged writes that completed prior to the start of the read operation. The query may wait for concurrently executing writes to propagate to a majority of replica set members before returning results. (MongoDB 3.4+)
- snapshot - Only available for operations within multi-document transactions. Upon transaction commit with write concern "majority", the transaction operations are guaranteed to have read from a snapshot of majority-committed data. (MongoDB 4.0+)

Aliases

- l local
- a available
- m majority
- lz linearizable
- s snapshot

Read more about how to use read concern here.

$3

Sets the writeConcern option for the query.

This option is only valid for operations that write to the database:

- deleteOne()
- deleteMany()
- findOneAndDelete()
- findOneAndUpdate()
- updateOne()
- updateMany()

`js
mquery().writeConcern(0)
mquery().writeConcern(1)
mquery().writeConcern({ w: 1, j: true, wtimeout: 2000 })
mquery().writeConcern('majority')
mquery().writeConcern('m') // same as majority
mquery().writeConcern('tagSetName') // if the tag set is 'm', use .writeConcern({ w: 'm' }) instead
mquery().w(1) // w is alias of writeConcern
`

#### Write Concern:

writeConcern({ w: , j: , wtimeout: })

- the w option to request acknowledgement that the write operation has propagated to a specified number of mongod instances or to mongod instances with specified tags
- the j option to request acknowledgement that the write operation has been written to the journal
- the wtimeout option to specify a time limit to prevent write operations from blocking indefinitely

Can be break down to use the following syntax:

mquery().w().j().wtimeout()

Read more about how to use write concern here

$3

Sets the slaveOk option. true allows reading from secondaries.

deprecated use read() preferences instead if on mongodb >= 2.2

``js
query.slaveOk() // true
query.slaveOk(true)
query.slaveOk(false)
`

MongoDB documentation

$3

Sets tailable option.

`js
mquery().tailable() <== true
mquery().tailable(true)
mquery().tailable(false)
`

_Cannot be used with distinct()._

MongoDB Documentation

$3

Specifies a time limit, in milliseconds, for the write concern. If w > 1, it is maximum amount of time to
wait for this write to propagate through the replica set before this operation fails. The default is 0, which means no timeout.

This option is only valid for operations that write to the database:

- deleteOne()
- deleteMany()
- findOneAndDelete()
- findOneAndUpdate()
- updateOne()
- updateMany()

Defaults to wtimeout value if it is specified in writeConcern

`js
mquery().wtimeout(2000)
mquery().wTimeout(2000)
`

Helpers

$3

Sets the querys collection.

`js
mquery().collection(aCollection)
`

$3

Executes the query and returns a promise which will be resolved with the query results or rejected if the query responds with an error.

`js
mquery().find(..).then(success, error);
`

This is very useful when combined with co or koa, which automatically resolve promise-like objects for you.

`js
co(function*(){
var doc = yield mquery().findOne({ _id: 499 });
console.log(doc); // { _id: 499, name: 'amazing', .. }
})();
`

_NOTE_:
The returned promise is a bluebird promise but this is customizable. If you want to
use your favorite promise library, simply set mquery.Promise = YourPromiseConstructor.
Your Promise must be promises A+ compliant.

$3

Merges other mquery or match condition objects into this one. When an mquery instance is passed, its match conditions, field selection and options are merged.

`js
const drum = mquery({ type: 'drum' }).collection(instruments);
const redDrum = mquery({ color: 'red' }).merge(drum);
const n = await redDrum.count();
console.log('there are %d red drums', n);
`

Internally uses mquery.canMerge to determine validity.

$3

Sets query options.

`js
mquery().setOptions({ collection: coll, limit: 20 })
`

#### setOptions() options

- tailable *
- sort *
- limit *
- skip *
- maxTime *
- batchSize *
- comment *
- hint *
- collection: the collection to query against

_* denotes a query helper method is also available_

$3

Set a function to trace this query. Useful for profiling or logging.

`js
function traceFunction (method, queryInfo, query) {
console.log('starting ' + method + ' query');

return function (err, result, millis) {
console.log('finished ' + method + ' query in ' + millis + 'ms');
};
}

mquery().setTraceFunction(traceFunction).findOne({name: 'Joe'}, cb);
`

The trace function is passed (method, queryInfo, query)

- method is the name of the method being called (e.g. findOne)
- queryInfo contains information about the query:
- conditions: query conditions/criteria
- options: options such as sort, fields, etc
- doc: document being updated
- query is the query object

The trace function should return a callback function which accepts:
- err: error, if any
- result: result, if any
- millis: time spent waiting for query result

NOTE: stream requests are not traced.

$3

Similar to setTraceFunction() but automatically applied to all queries.

`js
mquery.setTraceFunction(traceFunction);
`

$3

Determines if conditions can be merged using mquery().merge().

`js
var query = mquery({ type: 'drum' });
var okToMerge = mquery.canMerge(anObject)
if (okToMerge) {
query.merge(anObject);
}
`

mquery.use$geoWithin

MongoDB 2.4 introduced the $geoWithin operator which replaces and is 100% backward compatible with $within. As of mquery 0.2, we default to using $geoWithin for all within() calls.

If you are running MongoDB < 2.4 this will be problematic. To force mquery to be backward compatible and always use $within, set the mquery.use$geoWithin flag to false.

`js
mquery.use$geoWithin = false;
`

Custom Base Queries

Often times we want custom base queries that encapsulate predefined criteria. With mquery this is easy. First create the query you want to reuse and call its toConstructor() method which returns a new subclass of mquery that retains all options and criteria of the original.

`js
var greatMovies = mquery(movieCollection).where('rating').gte(4.5).toConstructor();

// use it!
const n = await greatMovies().count();
console.log('There are %d great movies', n);

const docs = await greatMovies().where({ name: /^Life/ }).select('name').find();
console.log(docs);
`

Validation

Method and options combinations are checked for validity at runtime to prevent creation of invalid query constructs. For example, a distinct query does not support specifying options like hint or field selection. In this case an error will be thrown so you can catch these mistakes in development.

Debug support

Debug mode is provided through the use of the debug module. To enable:

`sh
DEBUG=mquery node yourprogram.js
`

Read the debug module documentation for more details.

General compatibility

$3

mquery clones query arguments before passing them to a collection method for execution.
This prevents accidental side-affects to the objects you pass.
To clone ObjectIds we need to make some assumptions.

First, to check if an object is an ObjectId, we check its constructors name. If it matches either
ObjectId or ObjectID we clone it.

To clone ObjectIds, we call its optional clone method. If a clone method does not exist, we fall
back to calling new obj.constructor(obj.id). We assume, for compatibility with the
Node.js driver, that the ObjectId instance has a public id property and that
when creating an ObjectId instance we can pass that id as an argument.

#### Read Preferences

mquery supports specifying Read Preferences to control from which MongoDB node your query will read.
The Read Preferences spec also support specifying tags. To pass tags, some
drivers (Node.js driver) require passing a special constructor that handles both the read preference and its tags.
If you need to specify tags, pass an instance of your drivers ReadPreference constructor or roll your own. mquery will store whatever you provide and pass later to your collection during execution.

Future goals

- mongo shell compatibility
- browser compatibility

Installation

`sh
npm install mquery
``

License

MIT