Ecto.Adapters.ClickHouse.Types.FixedString (clickhouse_adapter_ecto v0.1.0)

An Ecto.ParameterizedType for ClickHouse's FixedString(N) column type.

Use it in a schema the same way as any other parameterized type:

schema "widgets" do
  field :code, Ecto.Adapters.ClickHouse.Types.FixedString, size: 16
end

size (a positive integer, the N in FixedString(N)) is required and validated at init/1 time -- i.e. as soon as the schema module compiles, not the first time a value is cast.

Value semantics

FixedString(N) always occupies exactly N bytes on the wire: ClickHouse zero-pads a shorter value up to N on INSERT and rejects (raises DB::Exception code 131, "Too large string for FixedString column") a value longer than N bytes. SELECT returns those N bytes verbatim, padding included -- ClickHouse does not strip it back out.

This type mirrors that on both sides instead of silently reinterpreting it: cast/2 rejects (with a changeset-friendly {:error, ...}) a binary longer than size, but does not pad a shorter one itself -- ClickHouse's own INSERT already does that, so padding here too would just be duplicated, easy-to-drift logic. load/3 returns the padded bytes exactly as decoded (matching ChDriver.Protocol.NativeBlock's own decision to decode FixedString(N) to the raw N-byte binary rather than trimming it) -- trimming trailing 0x00 bytes here would silently discard real wire content for any caller intentionally storing binary data whose natural encoding ends in zero bytes.