Represents a Duration
A builtin type that can be referenced via :duration
Constraints
:units- The units permitted to be non-zero; any unit outside the set must be zero, otherwise casting fails. Either an explicit list of units, or a shorthand for one side of the comparability boundary::year_month([:year, :month]) or:day_time([:week, :day, :hour, :minute, :second, :microsecond]). Confining an attribute to a single side keeps its values comparable (seeAsh.Type.Duration.compare/2).
Summary
Functions
Compares two durations as a total order, matching how the AshPostgres data
layer (PostgreSQL interval) compares them: a fixed conversion of month → 30
days and day → 24 hours (so year → 360 days, week → 7 days), down to
microseconds.
Functions
@spec compare(Duration.t(), Duration.t()) :: :lt | :eq | :gt
Compares two durations as a total order, matching how the AshPostgres data
layer (PostgreSQL interval) compares them: a fixed conversion of month → 30
days and day → 24 hours (so year → 360 days, week → 7 days), down to
microseconds.
Duration is only partially ordered in general — a month is not a fixed
number of days — which is why Elixir ships Duration without a compare/2, and
why data layers disagree on cross-unit comparison: PostgreSQL uses 30-day
months, Neo4j ~30.44-day months, and Elixir's to_timeout/1 refuses month/
year outright. This adopts PostgreSQL's convention so in-memory comparison
stays aligned with the dominant data layer rather than raising or drifting.
Within the day/time units, or within the year/month units, the result is exact
and portable across those backends; only comparison across that boundary
depends on the 30-day convention.
Computed from the integer fields directly, so microsecond precision is kept
(unlike to_timeout/1, which truncates to milliseconds).
This function is the single place the convention lives; if Elixir core later
gains a Duration.compare/2, it can delegate here.