Mylet set queries are used to perform CRUD operations on a set.

There are three places where they can be used:

• controller
• hook
• migrations

In controller and hook set queries can be initiated through mylet-query module:

var query = require('mylet-query');
query('history')
    .then(docs => /* here docs is an array of documents in history set */...)

In example above a query to history set is performed. The result-set of the query is accessed in then() callback.

In migrations set queries are accessed through entry point's first argument:

1. db.query('setname')

db.query('history')
    .then(docs => /* here docs is an array of documents in history set */...)

db.query() returns QueryBuilder interface.

2. db.addSet('setname') or db.renameSet('setname')

db.addSet('history')
    .insert({ id: 1, val: 'moved to Calgary' })
    .then(() => /* here history set already contains inserted document */...)

db.addSet() and db.renameSet() return SetBuilder interface.

Each query is build using query builder interfaces described below. Here is example of querying first 2 history documents where id property is greater than 4:

query('history')
   .where({ id: { $gt: 4 } })
   .take(2)
   .then(docs => ...)

At any step query builder is represented as:

1. builder itself, so it allows to call nested methods building desired query expression
2. a promise, so once then() or catch() methods a called built query is evaluated

Let's do another example to see how it works:

// get a query builder of history set
var history = query('history');

// get history query builder that represents only documents with id greater than 4
var historyGreaterThan4 = history.where({ id: { $gt: 4 } });

// lets create another one that contain only documents with id greater than 4 ordered by id property
var historyGreaterThan4Ordered = historyGreaterThan4.orderBy('id');

// at this point no queries are evaluated - we just built them

// lets evaluate all three queries we have using power of promises:
Promise.all([history, historyGreaterThan4, historyGreaterThan4Ordered])
    .spread((all, greaterThan4, greaterThan4Ordered) => /* queries are evaluated now */...);

NOTE: builder methods do not mutate current builder state, but instead return new builder with new state.

Below described set query builder interfaces that are returned depending on what builder methods are called.

Each builder has the following promise methods:

The interface is accessed by db.addSet() and db.renameSet() in migrations.

The interface is returned by query(), where() and db.query().

The interface is returned by orderBy() and select() methods.

The interface is returned by take() method.

The interface is returned by skip() method.

The interface is returned by skip().take() or by take().skip() methods.

The interface is returned by update() method.

The interface is returned by insert(), all(), any(), count(), first(), last() and single() methods.

The interface doesn't have builder methods - just promise ones: then() and catch().

Master set is a set that provides access to user records. This is read-only set, so insert(), update() and delete() methods throw corresponding error.

Master set has the following schema:

• time - UTC time when a record was added
• phrase - raw record phrase
• latitude
• longitude
• altitude

To specify equality condition, use the criteria { <field>: <value> } to select all documents that contain the with the specified .

A criteria can use the property operators to specify conditions. For example, { a: { $ne: 1 } } selects all documents where property a not equal to 1.

A compound criteria can specify conditions for more than one field in a document. Implicitly, a logical AND conjunction connects the clauses of a compound criteria so that the query selects the documents that match all the conditions. For example, { a: 1, b: 2 } selects all documents where a equals to 1 and b equals to 2.

Using the $and, $or and $not group operator, you can explicitly specify a compound criteria. For example, { $or: [{ a: 1 }, { a: 2 }] } selects all documents where property a equals to 1 or 2.

Supported group operators:

Supported property operators:

prop1 parameter in orderBy(prop1, ...) has the following options:

• a string - name of a property to order by ascendingly
• an object - { $asc: 'propName' } or { $desc: 'propName' } object that specify property and order direction