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scylladb/sstables/sstable_set_impl.hh
Raphael S. Carvalho c77f710a0c sstables: Fix quadratic space complexity in partitioned_sstable_set 
Interval map is very susceptible to quadratic space behavior when
it's flooded with many entries overlapping all (or most of)
intervals, since each such entry will have presence on all
intervals it overlaps with.

A trigger we observed was memtable flush storm, which creates many
small "L0" sstables that spans roughly the entire token range.

Since we cannot rely on insertion order, solution will be about
storing sstables with such wide ranges in a vector (unleveled).

There should be no consequence for single-key reads, since upper
layer applies an additional filtering based on token of key being
queried.
And for range scans, there can be an increase in memory usage,
but not significant because the sstables span an wide range and
would have been selected in the combined reader if the range of
scan overlaps with them.

Anyway, this is a protection against storm of memtable flushes
and shouldn't be the common scenario.

It works both with tablets and vnodes, by adjusting the token
range spanned by compaction group accordingly.

Fixes #23634.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
2025-04-29 15:47:33 -03:00

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/*
* Copyright (C) 2020-present ScyllaDB
*/
/*
* SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.0
*/
#pragma once
#include <boost/icl/interval_map.hpp>
#include "dht/ring_position.hh"
#include "sstable_set.hh"
#include "readers/clustering_combined.hh"
#include "sstables/types_fwd.hh"
namespace sstables {
// specialized when sstables are partitioned in the token range space
// e.g. leveled compaction strategy
class partitioned_sstable_set : public sstable_set_impl {
using value_set = std::unordered_set<shared_sstable>;
using interval_map_type = boost::icl::interval_map<dht::compatible_ring_position_or_view, value_set>;
using interval_type = interval_map_type::interval_type;
using map_iterator = interval_map_type::const_iterator;
private:
schema_ptr _schema;
std::vector<shared_sstable> _unleveled_sstables;
interval_map_type _leveled_sstables;
lw_shared_ptr<sstable_list> _all;
std::unordered_map<run_id, shared_sstable_run> _all_runs;
// Change counter on interval map for leveled sstables which is used by
// incremental selector to determine whether or not to invalidate iterators.
uint64_t _leveled_sstables_change_cnt = 0;
// Token range spanned by the compaction group owning this sstable set.
dht::token_range _token_range;
private:
static interval_type make_interval(const schema& s, const dht::partition_range& range);
interval_type make_interval(const dht::partition_range& range) const;
static interval_type make_interval(const schema_ptr& s, const sstable& sst);
interval_type make_interval(const sstable& sst);
interval_type singular(const dht::ring_position& rp) const;
std::pair<map_iterator, map_iterator> query(const dht::partition_range& range) const;
// SSTables are stored separately to avoid interval map's fragmentation issue when level 0 falls behind.
bool store_as_unleveled(const shared_sstable& sst) const;
public:
static dht::ring_position to_ring_position(const dht::compatible_ring_position_or_view& crp);
static dht::partition_range to_partition_range(const interval_type& i);
static dht::partition_range to_partition_range(const dht::ring_position_view& pos, const interval_type& i);
partitioned_sstable_set(const partitioned_sstable_set&) = delete;
explicit partitioned_sstable_set(schema_ptr schema, dht::token_range token_range);
// For cloning the partitioned_sstable_set (makes a deep copy, including *_all)
explicit partitioned_sstable_set(
schema_ptr schema,
const std::vector<shared_sstable>& unleveled_sstables,
const interval_map_type& leveled_sstables,
const lw_shared_ptr<sstable_list>& all,
const std::unordered_map<run_id, shared_sstable_run>& all_runs,
dht::token_range token_range,
uint64_t bytes_on_disk);
virtual std::unique_ptr<sstable_set_impl> clone() const override;
virtual std::vector<shared_sstable> select(const dht::partition_range& range) const override;
virtual std::vector<frozen_sstable_run> all_sstable_runs() const override;
virtual lw_shared_ptr<const sstable_list> all() const override;
virtual stop_iteration for_each_sstable_until(std::function<stop_iteration(const shared_sstable&)> func) const override;
virtual future<stop_iteration> for_each_sstable_gently_until(std::function<future<stop_iteration>(const shared_sstable&)> func) const override;
virtual bool insert(shared_sstable sst) override;
virtual bool erase(shared_sstable sst) override;
virtual size_t size() const noexcept override;
virtual sstable_set_impl::selector_and_schema_t make_incremental_selector() const override;
class incremental_selector;
};
class time_series_sstable_set : public sstable_set_impl {
private:
using container_t = std::multimap<position_in_partition, shared_sstable, position_in_partition::less_compare>;
schema_ptr _schema;
schema_ptr _reversed_schema; // == _schema->make_reversed();
bool _enable_optimized_twcs_queries;
// s.min_position() -> s, ordered using _schema
lw_shared_ptr<container_t> _sstables;
// s.max_position().reversed() -> s, ordered using _reversed_schema; the set of values is the same as in _sstables
lw_shared_ptr<container_t> _sstables_reversed;
public:
time_series_sstable_set(schema_ptr schema, bool enable_optimized_twcs_queries);
time_series_sstable_set(const time_series_sstable_set& s);
virtual std::unique_ptr<sstable_set_impl> clone() const override;
virtual std::vector<shared_sstable> select(const dht::partition_range& range = query::full_partition_range) const override;
virtual lw_shared_ptr<const sstable_list> all() const override;
virtual stop_iteration for_each_sstable_until(std::function<stop_iteration(const shared_sstable&)> func) const override;
virtual future<stop_iteration> for_each_sstable_gently_until(std::function<future<stop_iteration>(const shared_sstable&)> func) const override;
virtual bool insert(shared_sstable sst) override;
virtual bool erase(shared_sstable sst) override;
virtual size_t size() const noexcept override;
virtual sstable_set_impl::selector_and_schema_t make_incremental_selector() const override;
std::unique_ptr<position_reader_queue> make_position_reader_queue(
std::function<mutation_reader(sstable&)> create_reader,
std::function<bool(const sstable&)> filter,
partition_key pk, schema_ptr schema, reader_permit permit,
streamed_mutation::forwarding fwd_sm,
bool reversed) const;
virtual mutation_reader create_single_key_sstable_reader(
replica::column_family*,
schema_ptr,
reader_permit,
utils::estimated_histogram&,
const dht::partition_range&,
const query::partition_slice&,
tracing::trace_state_ptr,
streamed_mutation::forwarding,
mutation_reader::forwarding,
const sstable_predicate&) const override;
friend class sstable_position_reader_queue;
};
// this compound set holds reference to N sstable sets and allow their operations to be combined.
// the managed sets cannot be modified through compound_sstable_set, but only jointly read from, so insert() and erase() are disabled.
class compound_sstable_set : public sstable_set_impl {
schema_ptr _schema;
std::vector<lw_shared_ptr<sstable_set>> _sets;
public:
compound_sstable_set(schema_ptr schema, std::vector<lw_shared_ptr<sstable_set>> sets);
virtual std::unique_ptr<sstable_set_impl> clone() const override;
virtual std::vector<shared_sstable> select(const dht::partition_range& range = query::full_partition_range) const override;
virtual std::vector<frozen_sstable_run> all_sstable_runs() const override;
virtual lw_shared_ptr<const sstable_list> all() const override;
virtual stop_iteration for_each_sstable_until(std::function<stop_iteration(const shared_sstable&)> func) const override;
virtual future<stop_iteration> for_each_sstable_gently_until(std::function<future<stop_iteration>(const shared_sstable&)> func) const override;
virtual bool insert(shared_sstable sst) override;
virtual bool erase(shared_sstable sst) override;
virtual size_t size() const noexcept override;
virtual uint64_t bytes_on_disk() const noexcept override;
virtual sstable_set_impl::selector_and_schema_t make_incremental_selector() const override;
virtual mutation_reader create_single_key_sstable_reader(
replica::column_family*,
schema_ptr,
reader_permit,
utils::estimated_histogram&,
const dht::partition_range&,
const query::partition_slice&,
tracing::trace_state_ptr,
streamed_mutation::forwarding,
mutation_reader::forwarding,
const sstable_predicate&) const override;
class incremental_selector;
};
} // namespace sstables
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