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42 lines
2 KiB
Elixir
42 lines
2 KiB
Elixir
defmodule AshPostgres.Timestamptz do
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@moduledoc """
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Implements the PostgresSQL [timestamptz](https://www.postgresql.org/docs/current/datatype-datetime.html) (aka `timestamp with time zone`) type.
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Postgres [*strongly recommends*](https://wiki.postgresql.org/wiki/Don%27t_Do_This#Don.27t_use_timestamp_.28without_time_zone.29) using this type instead of the standard timestamps/datetimes without a time zone. Generally speaking, it is best practice to use the [nanosecond-precision](`AshPostgres.TimestamptzUsec`) variant.
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The basic reason `timestamptz` exists is to guarantee that the precise moment in time is stored as microseconds since January 1st, 2000 in UTC. This guarantee eliminates many time arithmetic problems, and ensures portability.
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It does not actually store a timezone, in spite of the name. As far as Elixir/Ecto is concerned, it it always of type `DateTime` and set to UTC. Using this type ensures Postgres internally uses the same contract as Ecto's `:utc_datetime`, which is to always store `DateTime` in UTC. This is especially helpful if you need to do complex time arithmetic in SQL fragments, or build reports/materialized views that use localized time formatting.
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Using this type ubiquitously in your schemas is particularly beneficial for consistency, and this is currently [under consideration](https://github.com/ash-project/ash_postgres/issues/264) as a configuration option for the default datetime storage type.
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```elixir
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attribute :timestamp, AshPostgres.Timestamptz
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timestamps type: AshPostgres.Timestamptz
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```
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Alternatively, you can set up a shortname:
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```elixir
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# config.exs
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config :ash, :custom_types, timestamptz: AshPostgres.Timestamptz
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```
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After saving, you will need to run `mix compile ash --force`.
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```elixir
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attribute :timestamp, :timestamptz
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timestamps type: :timestamptz
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```
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"""
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use Ash.Type.NewType, subtype_of: :datetime, constraints: [precision: :second]
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@impl true
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def storage_type(_constraints) do
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:timestamptz
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end
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end
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