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compact and remove expired rows from cache on read

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when read from cache compact and expire row tombstones
remove expired empty rows from cache
do not expire range tombstones in this patch

Refs #2252, #6033

Closes #12917
This commit is contained in:
Alexey Novikov
2023-02-16 14:59:36 +03:00
committed by Tomasz Grabiec
parent b23361977b
commit ca4e7f91c6
8 changed files with 168 additions and 10 deletions
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77
cache_flat_mutation_reader.hh
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@@ -110,6 +110,9 @@ class cache_flat_mutation_reader final : public flat_mutation_reader_v2::impl {
flat_mutation_reader_v2* _underlying = nullptr;
flat_mutation_reader_v2_opt _underlying_holder;
gc_clock::time_point _read_time;
gc_clock::time_point _gc_before;
future<> do_fill_buffer();
future<> ensure_underlying();
void copy_from_cache_to_buffer();
@@ -178,6 +181,20 @@ class cache_flat_mutation_reader final : public flat_mutation_reader_v2::impl {
const schema& table_schema() {
return *_snp->schema();
}
gc_clock::time_point get_read_time() {
return _read_context.tombstone_gc_state() ? gc_clock::now() : gc_clock::time_point::min();
}
gc_clock::time_point get_gc_before(const schema& schema, dht::decorated_key dk, const gc_clock::time_point query_time) {
auto gc_state = _read_context.tombstone_gc_state();
if (gc_state) {
return gc_state->get_gc_before_for_key(schema.shared_from_this(), dk, query_time);
}
return gc_clock::time_point::min();
}
public:
cache_flat_mutation_reader(schema_ptr s,
dht::decorated_key dk,
@@ -196,6 +213,8 @@ public:
, _read_context_holder()
, _read_context(ctx) // ctx is owned by the caller, who's responsible for closing it.
, _next_row(*_schema, *_snp, false, _read_context.is_reversed())
, _read_time(get_read_time())
, _gc_before(get_gc_before(*_schema, dk, _read_time))
{
clogger.trace("csm {}: table={}.{}, reversed={}, snap={}", fmt::ptr(this), _schema->ks_name(), _schema->cf_name(), _read_context.is_reversed(),
fmt::ptr(&*_snp));
@@ -730,9 +749,40 @@ void cache_flat_mutation_reader::copy_from_cache_to_buffer() {
}
}
// We add the row to the buffer even when it's full.
// This simplifies the code. For more info see #3139.
if (_next_row_in_range) {
bool remove_row = false;
if (_read_context.tombstone_gc_state() // do not compact rows when tombstone_gc_state is not set (used in some unit tests)
&& !_next_row.dummy()
&& _snp->at_latest_version()
&& _snp->at_oldest_version()) {
deletable_row& row = _next_row.latest_row();
auto t = row.deleted_at();
auto row_tomb_expired = [&](row_tombstone tomb) {
return (tomb && tomb.max_deletion_time() < _gc_before);
};
auto is_row_dead = [&](const deletable_row& row) {
auto& m = row.marker();
return (!m.is_missing() && m.is_dead(_read_time) && m.deletion_time() < _gc_before);
};
if (row_tomb_expired(t) || is_row_dead(row)) {
can_gc_fn always_gc = [&](tombstone) { return true; };
const schema& row_schema = _next_row.latest_row_schema();
_read_context.cache()._tracker.on_row_compacted();
with_allocator(_snp->region().allocator(), [&] {
deletable_row row_copy(row_schema, row);
row_copy.compact_and_expire(row_schema, t.tomb(), _read_time, always_gc, _gc_before, nullptr);
std::swap(row, row_copy);
});
remove_row = row.empty();
}
}
if (_next_row.range_tombstone_for_row() != _current_tombstone) [[unlikely]] {
auto tomb = _next_row.range_tombstone_for_row();
auto new_lower_bound = position_in_partition::before_key(_next_row.position());
@@ -742,8 +792,31 @@ void cache_flat_mutation_reader::copy_from_cache_to_buffer() {
_current_tombstone = tomb;
_read_context.cache()._tracker.on_range_tombstone_read();
}
if (remove_row) {
_read_context.cache()._tracker.on_row_compacted_away();
_lower_bound = position_in_partition::after_key(*_schema, _next_row.position());
partition_snapshot_row_weakref row_ref(_next_row);
move_to_next_entry();
with_allocator(_snp->region().allocator(), [&] {
cache_tracker& tracker = _read_context.cache()._tracker;
if (row_ref->is_linked()) {
tracker.get_lru().remove(*row_ref);
}
row_ref->on_evicted(tracker);
});
_snp->region().allocator().invalidate_references();
_next_row.force_valid();
} else {
// We add the row to the buffer even when it's full.
// This simplifies the code. For more info see #3139.
add_to_buffer(_next_row);
move_to_next_entry();
}
} else {
move_to_next_range();
}

4
db/cache_tracker.hh
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@@ -68,6 +68,8 @@ public:
uint64_t pinned_dirty_memory_overload;
uint64_t range_tombstone_reads;
uint64_t row_tombstone_reads;
uint64_t rows_compacted;
uint64_t rows_compacted_away;
uint64_t active_reads() const {
return reads - reads_done;
@@ -115,6 +117,8 @@ public:
void on_row_merged_from_memtable() noexcept { ++_stats.rows_merged_from_memtable; }
void on_range_tombstone_read() noexcept { ++_stats.range_tombstone_reads; }
void on_row_tombstone_read() noexcept { ++_stats.row_tombstone_reads; }
void on_row_compacted() noexcept { ++_stats.rows_compacted; }
void on_row_compacted_away() noexcept { ++_stats.rows_compacted_away; }
void pinned_dirty_memory_overload(uint64_t bytes) noexcept;
allocation_strategy& allocator() noexcept;
logalloc::region& region() noexcept;

9
partition_snapshot_row_cursor.hh
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@@ -564,6 +564,15 @@ public:
return cr;
}
const schema& latest_row_schema() const noexcept {
return *_current_row[0].schema;
}
// Can be called only when cursor is valid and pointing at a row.
deletable_row& latest_row() const noexcept {
return _current_row[0].it->row();
}
// Can be called only when cursor is valid and pointing at a row.
void latest_row_prepare_hash() const {
_current_row[0].it->row().cells().prepare_hash(*_current_row[0].schema, column_kind::regular_column);

4
read_context.hh
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@@ -126,6 +126,7 @@ class read_context final : public enable_lw_shared_from_this<read_context> {
tracing::trace_state_ptr _trace_state;
mutation_reader::forwarding _fwd_mr;
bool _range_query;
const tombstone_gc_state* _tombstone_gc_state;
// When reader enters a partition, it must be set up for reading that
// partition from the underlying mutation source (_underlying) in one of two ways:
//
@@ -148,6 +149,7 @@ public:
reader_permit permit,
const dht::partition_range& range,
const query::partition_slice& slice,
const tombstone_gc_state* gc_state,
tracing::trace_state_ptr trace_state,
mutation_reader::forwarding fwd_mr)
: _cache(cache)
@@ -158,6 +160,7 @@ public:
, _trace_state(std::move(trace_state))
, _fwd_mr(fwd_mr)
, _range_query(!query::is_single_partition(range))
, _tombstone_gc_state(gc_state)
, _underlying(_cache, *this)
{
if (_slice.options.contains(query::partition_slice::option::reversed)) {
@@ -195,6 +198,7 @@ public:
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>(); }
const tombstone_gc_state* tombstone_gc_state() const { return _tombstone_gc_state; }
public:
future<> ensure_underlying() {
if (_underlying_snapshot) {

2
replica/table.cc
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@@ -261,7 +261,7 @@ table::make_reader_v2(schema_ptr s,
const auto bypass_cache = slice.options.contains(query::partition_slice::option::bypass_cache);
if (cache_enabled() && !bypass_cache && !(reversed && _config.reversed_reads_auto_bypass_cache())) {
if (auto reader_opt = _cache.make_reader_opt(s, permit, range, slice, std::move(trace_state), fwd, fwd_mr)) {
if (auto reader_opt = _cache.make_reader_opt(s, permit, range, slice, &_compaction_manager.get_tombstone_gc_state(), std::move(trace_state), fwd, fwd_mr)) {
readers.emplace_back(std::move(*reader_opt));
}
} else {

7
row_cache.cc
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@@ -140,6 +140,10 @@ cache_tracker::setup_metrics() {
sm::description("total amount of range tombstones processed during read")),
sm::make_counter("row_tombstone_reads", _stats.row_tombstone_reads,
sm::description("total amount of row tombstones processed during read")),
sm::make_counter("rows_compacted", _stats.rows_compacted,
sm::description("total amount of attempts to compact expired rows during read")),
sm::make_counter("rows_compacted_away", _stats.rows_compacted_away,
sm::description("total amount of compacted and removed rows during read")),
});
}
@@ -725,12 +729,13 @@ row_cache::make_reader_opt(schema_ptr s,
reader_permit permit,
const dht::partition_range& range,
const query::partition_slice& slice,
const tombstone_gc_state* gc_state,
tracing::trace_state_ptr trace_state,
streamed_mutation::forwarding fwd,
mutation_reader::forwarding fwd_mr)
{
auto make_context = [&] {
return std::make_unique<read_context>(*this, s, std::move(permit), range, slice, trace_state, fwd_mr);
return std::make_unique<read_context>(*this, s, std::move(permit), range, slice, gc_state, trace_state, fwd_mr);
};
if (query::is_single_partition(range) && !fwd_mr) {

15
row_cache.hh
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@@ -358,14 +358,16 @@ public:
// User needs to ensure that the row_cache object stays alive
// as long as the reader is used.
// The range must not wrap around.
flat_mutation_reader_v2 make_reader(schema_ptr s,
reader_permit permit,
const dht::partition_range& range,
const query::partition_slice& slice,
tracing::trace_state_ptr trace_state = nullptr,
streamed_mutation::forwarding fwd = streamed_mutation::forwarding::no,
mutation_reader::forwarding fwd_mr = mutation_reader::forwarding::no) {
if (auto reader_opt = make_reader_opt(s, permit, range, slice, std::move(trace_state), fwd, fwd_mr)) {
mutation_reader::forwarding fwd_mr = mutation_reader::forwarding::no,
const tombstone_gc_state* gc_state = nullptr) {
if (auto reader_opt = make_reader_opt(s, permit, range, slice, gc_state, std::move(trace_state), fwd, fwd_mr)) {
return std::move(*reader_opt);
}
[[unlikely]] return make_empty_flat_reader_v2(std::move(s), std::move(permit));
@@ -376,13 +378,18 @@ public:
reader_permit permit,
const dht::partition_range&,
const query::partition_slice&,
const tombstone_gc_state*,
tracing::trace_state_ptr trace_state = nullptr,
streamed_mutation::forwarding fwd = streamed_mutation::forwarding::no,
mutation_reader::forwarding fwd_mr = mutation_reader::forwarding::no);
flat_mutation_reader_v2 make_reader(schema_ptr s, reader_permit permit, const dht::partition_range& range = query::full_partition_range) {
flat_mutation_reader_v2 make_reader(schema_ptr s,
reader_permit permit,
const dht::partition_range& range = query::full_partition_range,
const tombstone_gc_state* gc_state = nullptr) {
auto& full_slice = s->full_slice();
return make_reader(std::move(s), std::move(permit), range, full_slice);
return make_reader(std::move(s), std::move(permit), range, full_slice, nullptr,
streamed_mutation::forwarding::no, mutation_reader::forwarding::no, gc_state);
}
const stats& stats() const { return _stats; }

56
test/boost/row_cache_test.cc
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@@ -4543,3 +4543,59 @@ SEASTAR_THREAD_TEST_CASE(test_digest_read_during_schema_upgrade) {
m2.upgrade(s2);
assert_that(std::move(rd)).produces(m2);
}
SEASTAR_TEST_CASE(test_cache_compacts_expired_tombstones_on_read) {
return seastar::async([] {
auto s = schema_builder("ks", "cf")
.with_column("pk", int32_type, column_kind::partition_key)
.with_column("ck", int32_type, column_kind::clustering_key)
.with_column("v", int32_type)
.build();
tests::reader_concurrency_semaphore_wrapper semaphore;
auto pkey = tests::generate_partition_key(s);
auto make_ck = [&s] (int v) {
return clustering_key::from_deeply_exploded(*s, {data_value{v}});
};
auto make_prefix = [&s] (int v) {
return clustering_key_prefix::from_deeply_exploded(*s, {data_value{v}});
};
auto ck1 = make_ck(1);
auto ck2 = make_ck(2);
auto ck3 = make_ck(3);
auto dt_noexp = gc_clock::now();
auto dt_exp = gc_clock::now() - std::chrono::seconds(s->gc_grace_seconds().count() + 1);
auto mt = make_lw_shared<replica::memtable>(s);
cache_tracker tracker;
row_cache cache(s, snapshot_source_from_snapshot(mt->as_data_source()), tracker);
{
mutation m(s, pkey);
m.set_clustered_cell(ck1, "v", data_value(101), 1);
m.partition().apply_delete(*s, make_prefix(2), tombstone(1, dt_noexp)); // create non-expired tombstone
m.partition().apply_delete(*s, make_prefix(3), tombstone(2, dt_exp)); // create expired tombstone
cache.populate(m);
}
tombstone_gc_state gc_state(nullptr);
auto rd1 = cache.make_reader(s, semaphore.make_permit(), query::full_partition_range, &gc_state);
auto close_rd = deferred_close(rd1);
rd1.fill_buffer().get(); // cache_flat_mutation_reader compacts cache on fill buffer
cache_entry& entry = cache.lookup(pkey);
auto& cp = entry.partition().version()->partition();
BOOST_REQUIRE(cp.find_row(*s, ck1) != nullptr); // live row is in cache
BOOST_REQUIRE_EQUAL(cp.clustered_row(*s, ck2).deleted_at(), row_tombstone(tombstone(1, dt_noexp))); // non-expired tombstone is in cache
BOOST_REQUIRE(cp.find_row(*s, ck3) == nullptr); // expired tombstone isn't in cache
// check tracker stats
auto &tracker_stats = tracker.get_stats();
BOOST_REQUIRE(tracker_stats.rows_compacted == 1);
BOOST_REQUIRE(tracker_stats.rows_compacted_away == 1);
});
}