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row_cache: Allow specifying desired snapshot in autoupdating_underlying_reader

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When reading from incomplete partition entry, we may discover we need
to read something from the underlying mutation source. In such case we
will fast forward this reader to that partition. But we must do it
using a specific snapshot, the one we obtained when entering the
partition, not the latest one.
This commit is contained in:
Tomasz Grabiec
2017-06-12 13:19:26 +02:00
parent a1d3e0318c
commit 69ea29131f
1 changed files with 15 additions and 2 deletions
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17
read_context.hh
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@@ -47,6 +47,16 @@ public:
: _cache(cache)
, _read_context(context)
{ }
// Reads next partition without changing mutation source snapshot.
future<streamed_mutation_opt> read_next_same_phase() {
_last_key = std::move(_new_last_key);
return (*_reader)().then([this] (auto&& smopt) {
if (smopt) {
_new_last_key = smopt->decorated_key();
}
return std::move(smopt);
});
}
future<streamed_mutation_opt> operator()() {
_last_key = std::move(_new_last_key);
auto start = population_range_start();
@@ -73,14 +83,17 @@ public:
});
}
future<> fast_forward_to(dht::partition_range&& range) {
auto snapshot_and_phase = _cache.snapshot_of(dht::ring_position_view::for_range_start(_range));
return fast_forward_to(std::move(range), snapshot_and_phase.snapshot, snapshot_and_phase.phase);
}
future<> fast_forward_to(dht::partition_range&& range, mutation_source& snapshot, row_cache::phase_type phase) {
_range = std::move(range);
_last_key = { };
_new_last_key = { };
auto phase = _cache.phase_of(dht::ring_position_view::for_range_start(_range));
if (_reader && _reader_creation_phase == phase) {
return _reader->fast_forward_to(_range);
}
_reader = _cache.create_underlying_reader(_read_context, _cache.snapshot_for_phase(phase), _range);
_reader = _cache.create_underlying_reader(_read_context, snapshot, _range);
_reader_creation_phase = phase;
return make_ready_future<>();
}