View Source Expressions

In addition to the expressions listed in the Ash expressions guide, AshPostgres provides the following expressions


Fragments allow you to use arbitrary postgres expressions in your queries. Fragments can often be an escape hatch to allow you to do things that don't have something officially supported with Ash.


Simple expressions

fragment("? / ?", points, count)

Calling functions

fragment("repeat('hello', 4)")

Using entire queries

fragment("points > (SELECT SUM(points) FROM games WHERE user_id = ? AND id != ?)", user_id, id)

a last resport

Using entire queries as shown above is a last resort, but can sometimes be the best way to accomplish a given task.

In calculations

calculations do
  calculate :lower_name, :string, expr(
    fragment("LOWER(?)", name)

In migrations

create table(:managers, primary_key: false) do
  add :id, :uuid, null: false, default: fragment("UUID_GENERATE_V4()"), primary_key: true

Like and ILike

These wrap the postgres builtin like and ilike operators.

Please be aware, these match patterns not raw text. Use contains/1 if you want to match text without supporting patterns, i.e % and _ have semantic meaning!

For example:

Ash.Query.filter(User, like(name, "%obo%")) # name contains obo anywhere in the string, case sensitively
Ash.Query.filter(User, ilike(name, "%ObO%")) # name contains ObO anywhere in the string, case insensitively

Trigram similarity

To use this expression, you must have the pg_trgm extension in your repos installed_extensions list.

This calls the similarity function from that extension. See more in the pgtrgm guide

For example:

Ash.Query.filter(User, trigram_similarity(first_name, "fred") > 0.8)