Selecto v0.4.3

Selecto

Alpha software. Expect API churn and breaking changes while the core package is still being hardened.

selecto is the core query engine in the Selecto ecosystem.

It gives you:

  • domain-driven query configuration
  • safe select/filter/group/order composition
  • automatic join resolution from configured relationships
  • aggregate and OLAP-style query support
  • CTEs, lateral joins, and other advanced SQL shapes
  • expression helpers and a named-function registry for reusable query AST

ecosystem

 Ecosystem

Use selecto with companion packages when you need more than the core engine:

  • selecto_components for Phoenix LiveView query UI
  • selecto_mix for domain generation and installation tasks
  • selecto_updato for write operations over Selecto domains
  • adapter packages such as selecto_db_postgresql, selecto_db_mysql, selecto_db_sqlite, and others
  • selecto_postgis for spatial/map extension support

installation

 Installation

Add selecto and the adapter package your app uses:

def deps do
  [
    {:selecto, ">= 0.4.3 and < 0.5.0"},
    {:selecto_db_postgresql, ">= 0.4.2 and < 0.5.0"}
  ]
end

quick-start

 Quick Start

Define a domain:

domain = %{
  name: "Orders",
  source: %{
    source_table: "orders",
    primary_key: :id,
    fields: [:id, :total, :customer_id, :created_at],
    columns: %{
      id: %{type: :integer},
      total: %{type: :decimal},
      customer_id: %{type: :integer},
      created_at: %{type: :utc_datetime}
    },
    associations: %{
      customer: %{queryable: :customers, field: :customer, owner_key: :customer_id, related_key: :id}
    }
  },
  schemas: %{
    customers: %{
      source_table: "customers",
      fields: [:id, :name],
      columns: %{
        id: %{type: :integer},
        name: %{type: :string}
      }
    }
  },
  joins: %{
    customer: %{type: :star_dimension, display_field: :name}
  }
}

Build and run a query:

selecto = Selecto.configure(domain, Repo)

{:ok, {rows, columns, aliases}} =
  selecto
  |> Selecto.select(["id", "total", "customer.name"])
  |> Selecto.filter([{"total", {:gt, 100}}])
  |> Selecto.order_by(["created_at"])
  |> Selecto.execute()

expression-helpers

 Expression Helpers

Use Selecto.Expr when query structure is assembled dynamically in Elixir:

alias Selecto.Expr, as: X

query =
  selecto
  |> Selecto.filter(
    X.compact_and([
      X.eq("status", "active"),
      X.when_present(search, &X.ilike("customer.name", "%#{&1}%")),
      X.gte("total", 100)
    ])
  )
  |> Selecto.select([
    X.field("id"),
    X.field("customer.name"),
    X.as(X.count("*"), "row_count")
  ])

For lighter authoring, Selecto also ships macro and sigil support. See docs/expression_dsl.md for the detailed guide.

named-functions-udf-registry

 Named Functions (UDF Registry)

Selecto domains can register named database functions under domain[:functions].

That lets you reuse typed scalar, predicate, and table-function definitions instead of scattering raw SQL fragments through your code.

domain = %{
  # ...
  functions: %{
    "name_lower" => %{
      kind: :scalar,
      sql_name: "lower",
      returns: :string,
      allowed_in: [:select, :order_by],
      args: [%{name: :value, type: :string, source: :selector}]
    }
  }
}

query =
  selecto
  |> Selecto.select([
    "name",
    Selecto.Expr.as(Selecto.udf("name_lower", ["name"]), "normalized_name")
  ])

UDF-backed custom columns are also supported through custom_columns[*].select.

extensions

 Extensions

Selecto supports extension packages through the :extensions key on domains.

Example with PostGIS:

domain = %{
  # ...
  extensions: [Selecto.Extensions.PostGIS]
}

Use extensions when a package needs to contribute domain metadata, overlay DSL, adapter type mapping, or companion-package integrations.

status

 Status

Current 0.4.x scope:

  • core query building is usable but not stable
  • advanced subfilter internals are still high-risk/experimental
  • adapter support exists across multiple databases, but PostgreSQL remains the most complete path
  • schema/domain generation and UI are intentionally outside this package and live in companion repos

demos-and-tutorials

 Demos And Tutorials

  • selecto_livebooks for guided notebooks
  • selecto_northwind for tutorial-style examples
  • testselecto.fly.dev for a hosted demo app
  • selecto_components
  • selecto_mix
  • selecto_updato
  • selecto_postgis
  • selecto_test