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strong_consistency: classify reads by consistency level

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Introduce a read_type enum (linearizable vs non_linearizable) and transform
the existing "validate" function into a "parse" method - instead of checking
if the consistency level is one of the accepted ones, we now also return the
correcponding read type for strong consistency.
The "parse" function maps CQL consistency levels to following read types:
- CL=(LOCAL_)QUORUM -> linearizable (this is the default CL)
- CL=(LOCAL_)ONE -> non_linearizable
- all others -> throw

The classification is performed in the CQL layer (select_statement) to
keep the coordinator free of CL concepts.
This commit is contained in:
Wojciech Mitros
2026-04-21 03:28:07 +02:00
parent 1f91524547
commit c0ea98f922
3 changed files with 27 additions and 5 deletions
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16
cql3/statements/strong_consistency/select_statement.cc
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@@ -18,9 +18,15 @@ namespace cql3::statements::strong_consistency {
using result_message = cql_transport::messages::result_message;
static void validate_consistency_level(const db::consistency_level& cl) {
if (cl != db::consistency_level::QUORUM && cl != db::consistency_level::LOCAL_QUORUM &&
cl != db::consistency_level::ONE && cl != db::consistency_level::LOCAL_ONE) {
static service::strong_consistency::read_type parse_consistency_level(const db::consistency_level& cl) {
switch (cl) {
case db::consistency_level::QUORUM:
case db::consistency_level::LOCAL_QUORUM:
return service::strong_consistency::read_type::linearizable;
case db::consistency_level::ONE:
case db::consistency_level::LOCAL_ONE:
return service::strong_consistency::read_type::non_linearizable;
default:
throw exceptions::invalid_request_exception("Strongly consistent reads must use QUORUM/LOCAL_QUORUM or ONE/LOCAL_ONE consistency level");
}
}
@@ -29,7 +35,7 @@ future<::shared_ptr<result_message>> select_statement::do_execute(query_processo
service::query_state& state,
const query_options& options) const
{
validate_consistency_level(options.get_consistency());
auto read_type = parse_consistency_level(options.get_consistency());
const auto key_ranges = _restrictions->get_partition_key_ranges(options);
if (key_ranges.size() != 1 || !query::is_single_partition(key_ranges[0])) {
@@ -52,7 +58,7 @@ future<::shared_ptr<result_message>> select_statement::do_execute(query_processo
const auto timeout = db::timeout_clock::now() + get_timeout(state.get_client_state(), options);
auto [coordinator, holder] = qp.acquire_strongly_consistent_coordinator();
auto query_result = co_await coordinator.get().query(_query_schema, *read_command,
key_ranges, state.get_trace_state(), timeout, state.get_client_state().get_abort_source());
key_ranges, read_type, state.get_trace_state(), timeout, state.get_client_state().get_abort_source());
using namespace service::strong_consistency;
if (auto* redirect = get_if<need_redirect>(&query_result)) {