ChDriver.DBConnection (ch_driver v0.2.0)

DBConnection behaviour implementation for ClickHouse's native TCP protocol.

This is internal wiring: it's what makes ChDriver.start_link/1 and ChDriver.query/2,3,4 work as a normal pooled connection, but you should never call functions in this module directly. Use ChDriver's public API instead.

ClickHouse's native protocol is unpipelined request/response — one query in flight per socket at a time — so this module is a thin adapter over ChDriver.Connection: handle_execute/4 builds the final wire statement and params, runs the query, and translates the result into the shape DBConnection expects.

Socket-level failures disconnect the pooled connection so it gets torn down and reconnected; a ClickHouse-level query error (a rejected query, a syntax error, etc.) is returned as an ordinary error instead, since the connection itself is still fine to reuse.

There's no transaction support in ClickHouse's native protocol, so handle_begin/2, handle_commit/2, and handle_rollback/2 all return an error rather than pretending to do something.

Cursors

handle_declare/4, handle_fetch/4, and handle_deallocate/4 back ChDriver.stream/2,3,4: they read a query's result one block at a time via ChDriver.Connection.start_stream/3 / stream_fetch/2 / cancel_stream/2, instead of accumulating the whole thing into memory the way handle_execute/4 does.