ChDriver.Stream (ch_driver v0.1.0)

An Enumerable that lazily executes a query and yields its rows one ClickHouse wire-protocol Data block at a time, instead of buffering the whole result in memory the way ChDriver.query/2,3,4 does.

Built by ChDriver.stream/2,3,4 -- see its docs for why conn must already be a checked-out %DBConnection{} (obtained via DBConnection.run/3 or DBConnection.transaction/3), and for a usage example. All fields are private; this struct only exists so defimpl Enumerable below has something to dispatch on.

Reducing over a ChDriver.Stream delegates straight to DBConnection.reduce/3 via a plain %DBConnection.Stream{} (not DBConnection.PrepareStream) -- query is always a %ChDriver.Query{} struct, never a bare SQL string, so there's no separate "prepare first" path to distinguish the way Postgrex.Stream's Enumerable impl does for its two possible query shapes (see postgrex/lib/postgrex/stream.ex). DBConnection.reduce/3 drives ChDriver.DBConnection's handle_declare/4, handle_fetch/4, and handle_deallocate/4 (see their docs) via Stream.resource/3 under the hood, so cleanup (handle_deallocate/4) runs whether the consumer takes everything (Enum.to_list/1) or stops early (Enum.take/2, a break out of a for, an exception, ...).

Summary

Types

t()

Types

t()

@type t() :: %ChDriver.Stream{
  conn: DBConnection.conn(),
  opts: keyword(),
  params: list(),
  query: ChDriver.Query.t()
}