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•  package root

  

  

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

  Manual | scalamolecule.org | Github | Forum

  Definition Classes

  root

•  package molecule

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

  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
•  package ast

  Internal Molecule ASTs.

•  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.

•  package composition

  Methods to build transaction, composite and nested molecules.

•  package exceptions

  Exceptions thrown by 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

  See also

  Manual: expressions | aggregates | input molecules

  Tests: expressions

•  package facade
•  package factory

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

•  package generic
•  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)

•  package macros
•  package ops

  Internal operational helpers for transforming DSL to molecules.

•  package schema

  Schema definition DSL and API.

•  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

  See also

  http://www.scalamolecule.org/dev/transformation/

•  package util

  Internal database functions for Datomic.

molecule