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read_context: add _partition_exists

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This new state stores the information whether current partition
represented by _key is present in underlying.

Refs #8435.

Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
(cherry picked from commit ceab5f026d)
This commit is contained in:
Piotr Jastrzebski
2021-04-12 20:57:15 +02:00
committed by Kamil Braun
parent bbada5b9e4
commit d14ec86e7d
1 changed files with 12 additions and 1 deletions
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13
read_context.hh
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@@ -141,6 +141,7 @@ class read_context final : public enable_lw_shared_from_this<read_context> {
mutation_source_opt _underlying_snapshot;
dht::partition_range _sm_range;
std::optional<dht::decorated_key> _key;
bool _partition_exists;
row_cache::phase_type _phase;
public:
read_context(row_cache& cache,
@@ -189,15 +190,23 @@ public:
autoupdating_underlying_reader& underlying() { return _underlying; }
row_cache::phase_type phase() const { return _phase; }
const dht::decorated_key& key() const { return *_key; }
bool partition_exists() const { return _partition_exists; }
void on_underlying_created() { ++_underlying_created; }
bool digest_requested() const { return _slice.options.contains<query::partition_slice::option::with_digest>(); }
public:
future<> ensure_underlying(db::timeout_clock::time_point timeout) {
if (_underlying_snapshot) {
return create_underlying(timeout).then([this, timeout] {
return _underlying.underlying()(timeout).discard_result();
return _underlying.underlying()(timeout).then([this] (mutation_fragment_opt&& mfopt) {
_partition_exists = bool(mfopt);
});
});
}
// We know that partition exists because all the callers of
// enter_partition(const dht::decorated_key&, row_cache::phase_type)
// check that and there's no other way of setting _underlying_snapshot
// to empty. Except for calling create_underlying.
_partition_exists = true;
return make_ready_future<>();
}
public:
@@ -207,6 +216,8 @@ public:
_underlying_snapshot = snapshot;
_key = dk;
}
// Precondition: each caller needs to make sure that partition with |dk| key
// exists in underlying before calling this function.
void enter_partition(const dht::decorated_key& dk, row_cache::phase_type phase) {
_phase = phase;
_underlying_snapshot = {};