Packages

Documentation/API for the Molecule library - a meta DSL for the Datomic database.

Manual | scalamolecule.org | Github | Forum

Definition Classes: root

Molecule library - a Scala meta-DSL for the Datomic database.

See api package for various api imports to start using Molecule.

Sub-packages

api		Molecule API.
ast		Internal Molecule ASTs.
boilerplate		Internal interfaces for auto-generated DSL boilerplate code.
composition		Builder methods to compose molecules.
exceptions		Exceptions thrown by Molecule.
expression		Attribute expressions and operations.
facade		Molecule facades to Datomic.
factory		Implicit macro methods `m` to instantiate molecules from custom DSL molecule constructs.
input		Input molecules awaiting input.
macros		Internal macros generating molecule code from custom DSL molecule constructs.
generic		Interfaces to generic information about datoms and Datomic database.
ops		Internal operational helpers for transforming DSL to molecule.
schema		Schema definition DSL.
transform		Internal transformers from DSL to Model/Query/Transaction.
util		Internal Java database functions for Datomic.

Definition Classes: root

package api

Definition Classes: molecule

package ast

Internal Molecule ASTs.

Definition Classes: molecule

package boilerplate

Internal interfaces for auto-generated DSL boilerplate code.

Internal interfaces for auto-generated DSL boilerplate code.

Interfaces to the generated schema-defined DSL boilerplate code that the sbt-plugin generates when doing a sbt-compile. Molecule macros can then type-safely deduct the type structure of composed molecules.

Definition Classes: molecule

package composition

Methods to build transaction, composite and nested molecules.

Definition Classes: molecule

package exceptions

Exceptions thrown by Molecule.

Definition Classes: molecule

package expression

Attribute expressions and operations.

Attribute expressions and operations.

Refine attribute matches with various attribute expressions:

Person.age(42)                           // equality
Person.name.contains("John")             // fulltext search
Person.age.!=(42)                        // negation (or `not`)
Person.age.<(42)                         // comparison (< > <= >=)
Person.name("John" or "Jonas")           // OR-logic
Person.age()                             // apply empty value to retract value(s) in updates
Person.hobbies.assert("golf")               // add value(s) to card-many attributes
Person.hobbies.retract("golf")            // retract value(s) of card-many attributes
Person.hobbies.replace("golf", "diving") // replace value(s) of card-many attributes
Person.tags.k("en")                      // match values of map attributes by key
Person.age(Nil)                          // match non-asserted datoms (null)
Person.name(?)                           // initiate input molecules awaiting input at runtime
Person.name(unify)                       // Unify attributes in self-joins

Apply aggregate keywords to aggregate attribute value(s):

// Aggregates on any attribute type
Person.age(count).get.head         === 3   // count of asserted `age` attribute values
Person.age(countDistinct).get.head === 3   // count of asserted distinct `age` attribute values
Person.age(max).get.head           === 38  // maximum `age` value (using `compare`)
Person.age(min).get.head           === 5   // maximum `age` value (using `compare`)
Person.age(rand).get.head          === 25  // single random `age` value
Person.age(sample).get.head        === 27  // single sample `age` value (when single value, same as random)

// Aggregates on any attribute type, returning multiple values
Person.age(distinct).get.head  === Vector(5, 7, 38)  // distinct `age` values
Person.age(max(2)).get.head    === Vector(38, 7)     // 2 maximum `age` values
Person.age(min(2)).get.head    === Vector(5, 7)      // 2 minimum `age` values
Person.age(rand(2)).get.head   === Stream(5, ?)      // 2 random `age` values (values can re-occur)
Person.age(sample(2)).get.head === Vector(7, 38)     // 2 sample `age` values

// Aggregates on number attributes
Person.age(sum).get.head      === 50               // sum of all `age` numbers
Person.age(avg).get.head      === 16.66666667      // average of all `age` numbers
Person.age(median).get.head   === 7                // median of all `age` numbers
Person.age(stddev).get.head   === 15.107025591499  // standard deviation of all `age` numbers
Person.age(variance).get.head === 228.2222222222   // variance of all `age` numbers

Definition Classes: molecule
See also: Manual: expressions | aggregates | input molecules
Tests: expressions

package facade

Definition Classes: molecule

package factory

Factory methods m to instantiate molecules from custom DSL molecule constructs.

Definition Classes: molecule

package generic

Definition Classes: molecule

package input

Input molecules awaiting input.

Input molecules awaiting input.

Input molecules are molecules that awaits one or more inputs at runtime. When input value is applied, the input molecule is resolved and a standard molecule is returned that we can then call actions on.

Input molecule queries are cached by Datomic. So there is a runtime performance gain in using input molecules. Furthermore, input molecules are a good fit for re-use for queries where only a few parameters change.

Input molecules can await 1, 2 or 3 inputs and are constructed by applying the ? marker to attributes. If one marker is applied, we get a InputMolecule_1, 2 inputs creates an InputMolecule_2 and 3 an InputMolecule_3.

The three input molecule interfaces come in arity-versions corresponding to the number of non-?-marked attributes in the input molecule. Let's see a simple example:

// Sample data
Person.name.age insert List(("Ben", 42), ("Liz", 34))

// Input molecule created at compile time. Awaits a name of type String
val ageOfPersons: InputMolecule_1.InputMolecule_1_01[String, Int] = m(Person.name_(?).age)

// Resolved molecule. "Ben" input is matched against name attribute
val ageOfPersonsNamedBen: Molecule.Molecule01[Int] = ageOfPersons.apply("Ben")

// Calling action on resolved molecule.
// (Only age is returned since name was marked as tacit with the underscore notation)
ageOfPersonsNamedBen.get === List(42)

// Or we can re-use the input molecule straight away
ageOfPersons("Liz").get === List(34)

Definition Classes: molecule

package macros

Definition Classes: molecule

package ops

Internal operational helpers for transforming DSL to molecules.

Definition Classes: molecule

package schema

Schema definition DSL and API.

Definition Classes: molecule

package transform

Internal transformers from DSL to Model/Query/Transaction/Datomic.

Internal transformers from DSL to Model/Query/Transaction/Datomic.

Molecule transforms custom boilerplate DSL constructs to Datomic queries in 3 steps:

Custom DSL molecule --> Model --> Query --> Datomic query string