Selection.md

Selection

• Connection
• Pool

Managers

• Backup Manager

Utilities

• Transaction
• Selection
• Schema

An unchanged piece of the database in memory, to use as baseline of various endpoints to execute functions with.

const Selection = MyDB.Select(User => User.Age > 20);

A Selection allows you to filter something from the database, and perform methods such as sorting, limiting and iterating to grab results and leave the database unchanged.

Values

.cache

Cached dataset of this Selection. [Read Only]

Type {Collection}

.holds

Reference to the table this Selection holds. [Read Only]

Type {String}

.keys

Serialises this Selection's keys into an array.

Type {Array}

.values

Serialises this Selection's values into an array.

Type {Array}

.asObject

Serialises this Selection into an object.

Type {Object}

Methods

.retrieve(keyOrPath)

Returns the given document by its key from this Selection.

Key	Type	Description
keyOrPath	Pathlike	Indicates which (nested) element to receieve.

Returns {Object|Array|DataModel}

.order(predicate, preset?)

Sorts this Selection's values. Identical to the ORDER BY SQL statement.

Key	Type	Description
predicate	Function	Function which either determines the sort order with given arguments a and b when the preset is arbitrary, or a function to the target property to automatically sort with.
preset?	Order	A sort order, an enum from QDB being ascending, descending or arbitrary (default).

Returns {Selection}

.filter(predicate)

Filters values that satisfy the provided function. Identical to the FILTER BY SQL statement.

Key	Type	Description
predicate	Function	Function that determines which entries to keep.

Returns {Selection}

.limit(begin, end?)

Slices off values from this Selection. Identical to the LIMIT SQL statement.

Key	Type	Description
begin	Number	Index that indicates the beginning to slice.
end?	Number	An index for the end of the slice.

Returns {Selection}

.group(keyOrPath)

Groups this Selection based on an identifier. Identical to the GROUP BY SQL statement.

Key	Type	Description
keyOrPath	Pathlike	Determines by which property to group this Selection.

Returns {Selection}

.join(secondary, field, property?)

Joins another Selection into this instance based on a referrer field. Identical to the FULL JOIN SQL statement.

Key	Type	Description
secondary	Selection	Another Selection instance to join into this one.
field	String	Which field to check for a reference to this Selection's rows, or null to join with keys.
property?	Boolean, String	Boolean false to flatten the entries into this Selection's rows, a string value that implicitly indicates the property to add the merging entries, or a boolean true to use the Selection's table name as property.

Returns {Selection}

.map(fn)

Iterates over this Selection's values and keys, and implements the new values returned from the callback.

Key	Type	Description
fn	Function	Callback function which determines the new values of the Selection.

Returns {Selection}

.merge(selections)

Automatically clones the merging Selections and adds them into this instance.

Key	Type	Description
selections	...Selection	Instances to clone and merge into this one.

Returns {Selection}

.clone(holds?)

Creates a new memory allocation for the copy of this Selection.

Key	Type	Description
holds?	String	Optional new identifier value for the cloned Selection.

Returns {Selection}