0b418fa7cf
The CQL binary protocol introduced "unset" values in version 4
of the protocol. Unset values can be bound to variables, which
cause certain CQL fragments to be skipped. For example, the
fragment `SET a = :var` will not change the value of `a` if `:var`
is bound to an unset value.
Unsets, however, are very limited in where they can appear. They
can only appear at the top-level of an expression, and any computation
done with them is invalid. For example, `SET list_column = [3, :var]`
is invalid if `:var` is bound to unset.
This causes the code to be littered with checks for unset, and there
are plenty of tests dedicated to catching unsets. However, a simpler
way is possible - prevent the infiltration of unsets at the point of
entry (when evaluating a bind variable expression), and introduce
guards to check for the few cases where unsets are allowed.
This is what this long patch does. It performs the following:
(general)
1. unset is removed from the possible values of cql3::raw_value and
cql3::raw_value_view.
(external->cql3)
2. query_options is fortified with a vector of booleans,
unset_bind_variable_vector, where each boolean corresponds to a bind
variable index and is true when it is unset.
3. To avoid churn, two compatiblity structs are introduced:
cql3::raw_value{,_view}_vector_with_unset, which can be constructed
from a std::vector<raw_value{,_view/}>, which is what most callers
have. They can also be constructed with explicit unset vectors, for
the few cases they are needed.
(cql3->variables)
4. query_options::get_value_at() now throws if the requested bind variable
is unset. This replaces all the throwing checks in expression evaluation
and statement execution, which are removed.
5. A new query_options::is_unset() is added for the users that can tolerate
unset; though it is not used directly.
6. A new cql3::unset_operation_guard class guards against unsets. It accepts
an expression, and can be queried whether an unset is present. Two
conditions are checked: the expression must be a singleton bind
variable, and at runtime it must be bound to an unset value.
7. The modification_statement operations are split into two, via two
new subclasses of cql3::operation. cql3::operation_no_unset_support
ignores unsets completely. cql3::operation_skip_if_unset checks if
an operand is unset (luckily all operations have at most one operand that
tolerates unset) and applies unset_operation_guard to it.
8. The various sites that accept expressions or operations are modified
to check for should_skip_operation(). This are the loops around
operations in update_statement and delete_statement, and the checks
for unset in attributes (LIMIT and PER PARTITION LIMIT)
(tests)
9. Many unset tests are removed. It's now impossible to enter an
unset value into the expression evaluation machinery (there's
just no unset value), so it's impossible to test for it.
10. Other unset tests now have to be invoked via bind variables,
since there's no way to create an unset cql3::expr::constant.
11. Many tests have their exception message match strings relaxed.
Since unsets are now checked very early, we don't know the context
where they happen. It would be possible to reintroduce it (by adding
a format string parameter to cql3::unset_operation_guard), but it
seems not to be worth the effort. Usage of unsets is rare, and it is
explicit (at least with the Python driver, an unset cannot be
introduced by ommission).
I tried as an alternative to wrap cql3::raw_value{,_view} (that doesn't
recognize unsets) with cql3::maybe_unset_value (that does), but that
caused huge amounts of churn, so I abandoned that in favor of the
current approach.
Closes #12517
312 lines
16 KiB
C++
312 lines
16 KiB
C++
/*
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* Copyright (C) 2015-present ScyllaDB
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*
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* Modified by ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: (AGPL-3.0-or-later and Apache-2.0)
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*/
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#pragma once
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#include "cql3/statements/raw/select_statement.hh"
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#include "cql3/expr/unset.hh"
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#include "cql3/cql_statement.hh"
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#include "cql3/stats.hh"
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#include <seastar/core/shared_ptr.hh>
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#include "transport/messages/result_message.hh"
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#include "index/secondary_index_manager.hh"
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#include "exceptions/exceptions.hh"
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#include "exceptions/coordinator_result.hh"
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namespace service {
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class client_state;
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} // namespace service
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namespace cql3 {
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class query_processor;
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namespace selection {
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class selection;
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} // namespace selection
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namespace restrictions {
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class restrictions;
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class statement_restrictions;
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} // namespace restrictions
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namespace statements {
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/**
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* Encapsulates a completely parsed SELECT query, including the target
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* column family, expression, result count, and ordering clause.
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*
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*/
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class select_statement : public cql_statement {
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public:
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template<typename T>
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using coordinator_result = exceptions::coordinator_result<T>;
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using parameters = raw::select_statement::parameters;
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using ordering_comparator_type = raw::select_statement::ordering_comparator_type;
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static constexpr int DEFAULT_COUNT_PAGE_SIZE = 10000;
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protected:
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static thread_local const lw_shared_ptr<const parameters> _default_parameters;
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schema_ptr _schema;
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uint32_t _bound_terms;
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lw_shared_ptr<const parameters> _parameters;
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::shared_ptr<selection::selection> _selection;
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const ::shared_ptr<const restrictions::statement_restrictions> _restrictions;
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const bool _restrictions_need_filtering;
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::shared_ptr<std::vector<size_t>> _group_by_cell_indices; ///< Indices in result row of cells holding GROUP BY values.
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bool _is_reversed;
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expr::unset_bind_variable_guard _limit_unset_guard;
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std::optional<expr::expression> _limit;
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expr::unset_bind_variable_guard _per_partition_limit_unset_guard;
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std::optional<expr::expression> _per_partition_limit;
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template<typename T>
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using compare_fn = raw::select_statement::compare_fn<T>;
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using result_row_type = raw::select_statement::result_row_type;
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/**
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* The comparator used to orders results when multiple keys are selected (using IN).
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*/
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ordering_comparator_type _ordering_comparator;
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query::partition_slice::option_set _opts;
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cql_stats& _stats;
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const ks_selector _ks_sel;
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bool _range_scan = false;
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bool _range_scan_no_bypass_cache = false;
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std::unique_ptr<cql3::attributes> _attrs;
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private:
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future<shared_ptr<cql_transport::messages::result_message>> process_results_complex(foreign_ptr<lw_shared_ptr<query::result>> results,
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lw_shared_ptr<query::read_command> cmd, const query_options& options, gc_clock::time_point now) const;
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protected :
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virtual future<::shared_ptr<cql_transport::messages::result_message>> do_execute(query_processor& qp,
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service::query_state& state, const query_options& options) const;
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friend class select_statement_executor;
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public:
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select_statement(schema_ptr schema,
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uint32_t bound_terms,
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lw_shared_ptr<const parameters> parameters,
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::shared_ptr<selection::selection> selection,
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::shared_ptr<const restrictions::statement_restrictions> restrictions,
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::shared_ptr<std::vector<size_t>> group_by_cell_indices,
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bool is_reversed,
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ordering_comparator_type ordering_comparator,
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std::optional<expr::expression> limit,
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std::optional<expr::expression> per_partition_limit,
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cql_stats& stats,
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std::unique_ptr<cql3::attributes> attrs);
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virtual ::shared_ptr<const cql3::metadata> get_result_metadata() const override;
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virtual uint32_t get_bound_terms() const override;
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virtual future<> check_access(query_processor& qp, const service::client_state& state) const override;
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virtual void validate(query_processor&, const service::client_state& state) const override;
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virtual bool depends_on(std::string_view ks_name, std::optional<std::string_view> cf_name) const override;
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virtual future<::shared_ptr<cql_transport::messages::result_message>> execute(query_processor& qp,
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service::query_state& state, const query_options& options) const override;
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virtual future<::shared_ptr<cql_transport::messages::result_message>>
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execute_without_checking_exception_message(query_processor& qp, service::query_state& qs, const query_options& options) const override;
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future<::shared_ptr<cql_transport::messages::result_message>> execute(query_processor& qp,
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lw_shared_ptr<query::read_command> cmd, dht::partition_range_vector&& partition_ranges, service::query_state& state,
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const query_options& options, gc_clock::time_point now) const;
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future<::shared_ptr<cql_transport::messages::result_message>> execute_without_checking_exception_message(query_processor& qp,
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lw_shared_ptr<query::read_command> cmd, dht::partition_range_vector&& partition_ranges, service::query_state& state,
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const query_options& options, gc_clock::time_point now) const;
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struct primary_key {
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dht::decorated_key partition;
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clustering_key_prefix clustering;
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};
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future<shared_ptr<cql_transport::messages::result_message>> process_results(foreign_ptr<lw_shared_ptr<query::result>> results,
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lw_shared_ptr<query::read_command> cmd, const query_options& options, gc_clock::time_point now) const;
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const sstring& keyspace() const;
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const sstring& column_family() const;
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query::partition_slice make_partition_slice(const query_options& options) const;
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const ::shared_ptr<const restrictions::statement_restrictions> get_restrictions() const;
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bool has_group_by() const { return _group_by_cell_indices && !_group_by_cell_indices->empty(); }
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db::timeout_clock::duration get_timeout(const service::client_state& state, const query_options& options) const;
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protected:
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uint64_t do_get_limit(const query_options& options, const std::optional<expr::expression>& limit, const expr::unset_bind_variable_guard& unset_guard, uint64_t default_limit) const;
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uint64_t get_limit(const query_options& options) const {
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return do_get_limit(options, _limit, _limit_unset_guard, query::max_rows);
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}
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uint64_t get_per_partition_limit(const query_options& options) const {
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return do_get_limit(options, _per_partition_limit, _per_partition_limit_unset_guard, query::partition_max_rows);
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}
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bool needs_post_query_ordering() const;
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virtual void update_stats_rows_read(int64_t rows_read) const {
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_stats.rows_read += rows_read;
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}
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};
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class primary_key_select_statement : public select_statement {
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public:
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primary_key_select_statement(schema_ptr schema,
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uint32_t bound_terms,
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lw_shared_ptr<const parameters> parameters,
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::shared_ptr<selection::selection> selection,
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::shared_ptr<const restrictions::statement_restrictions> restrictions,
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::shared_ptr<std::vector<size_t>> group_by_cell_indices,
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bool is_reversed,
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ordering_comparator_type ordering_comparator,
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std::optional<expr::expression> limit,
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std::optional<expr::expression> per_partition_limit,
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cql_stats &stats,
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std::unique_ptr<cql3::attributes> attrs);
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};
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class indexed_table_select_statement : public select_statement {
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secondary_index::index _index;
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expr::expression _used_index_restrictions;
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schema_ptr _view_schema;
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noncopyable_function<dht::partition_range_vector(const query_options&)> _get_partition_ranges_for_posting_list;
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noncopyable_function<query::partition_slice(const query_options&)> _get_partition_slice_for_posting_list;
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public:
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static constexpr size_t max_base_table_query_concurrency = 4096;
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static ::shared_ptr<cql3::statements::select_statement> prepare(data_dictionary::database db,
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schema_ptr schema,
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uint32_t bound_terms,
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lw_shared_ptr<const parameters> parameters,
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::shared_ptr<selection::selection> selection,
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::shared_ptr<restrictions::statement_restrictions> restrictions,
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::shared_ptr<std::vector<size_t>> group_by_cell_indices,
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bool is_reversed,
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ordering_comparator_type ordering_comparator,
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std::optional<expr::expression> limit,
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std::optional<expr::expression> per_partition_limit,
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cql_stats &stats,
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std::unique_ptr<cql3::attributes> attrs);
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indexed_table_select_statement(schema_ptr schema,
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uint32_t bound_terms,
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lw_shared_ptr<const parameters> parameters,
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::shared_ptr<selection::selection> selection,
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::shared_ptr<const restrictions::statement_restrictions> restrictions,
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::shared_ptr<std::vector<size_t>> group_by_cell_indices,
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bool is_reversed,
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ordering_comparator_type ordering_comparator,
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std::optional<expr::expression> limit,
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std::optional<expr::expression> per_partition_limit,
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cql_stats &stats,
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const secondary_index::index& index,
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expr::expression used_index_restrictions,
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schema_ptr view_schema,
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std::unique_ptr<cql3::attributes> attrs);
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private:
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virtual future<::shared_ptr<cql_transport::messages::result_message>> do_execute(query_processor& qp,
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service::query_state& state, const query_options& options) const override;
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lw_shared_ptr<const service::pager::paging_state> generate_view_paging_state_from_base_query_results(lw_shared_ptr<const service::pager::paging_state> paging_state,
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const foreign_ptr<lw_shared_ptr<query::result>>& results, service::query_state& state, const query_options& options) const;
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future<coordinator_result<std::tuple<dht::partition_range_vector, lw_shared_ptr<const service::pager::paging_state>>>> find_index_partition_ranges(query_processor& qp,
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service::query_state& state,
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const query_options& options) const;
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future<coordinator_result<std::tuple<std::vector<primary_key>, lw_shared_ptr<const service::pager::paging_state>>>> find_index_clustering_rows(query_processor& qp,
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service::query_state& state,
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const query_options& options) const;
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future<shared_ptr<cql_transport::messages::result_message>>
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process_base_query_results(
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foreign_ptr<lw_shared_ptr<query::result>> results,
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lw_shared_ptr<query::read_command> cmd,
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service::query_state& state,
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const query_options& options,
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gc_clock::time_point now,
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lw_shared_ptr<const service::pager::paging_state> paging_state) const;
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lw_shared_ptr<query::read_command>
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prepare_command_for_base_query(query_processor& qp, const query_options& options, service::query_state& state, gc_clock::time_point now,
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bool use_paging) const;
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future<coordinator_result<std::tuple<foreign_ptr<lw_shared_ptr<query::result>>, lw_shared_ptr<query::read_command>>>>
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do_execute_base_query(
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query_processor& qp,
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dht::partition_range_vector&& partition_ranges,
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service::query_state& state,
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const query_options& options,
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gc_clock::time_point now,
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lw_shared_ptr<const service::pager::paging_state> paging_state) const;
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future<shared_ptr<cql_transport::messages::result_message>>
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execute_base_query(
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query_processor& qp,
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dht::partition_range_vector&& partition_ranges,
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service::query_state& state,
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const query_options& options,
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gc_clock::time_point now,
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lw_shared_ptr<const service::pager::paging_state> paging_state) const;
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// Function for fetching the selected columns from a list of clustering rows.
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// It is currently used only in our Secondary Index implementation - ordinary
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// CQL SELECT statements do not have the syntax to request a list of rows.
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// FIXME: The current implementation is very inefficient - it requests each
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// row separately (and, incrementally, in parallel). Even multiple rows from a single
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// partition are requested separately. This last case can be easily improved,
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// but to implement the general case (multiple rows from multiple partitions)
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// efficiently, we will need more support from other layers.
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// Keys are ordered in token order (see #3423)
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future<coordinator_result<std::tuple<foreign_ptr<lw_shared_ptr<query::result>>, lw_shared_ptr<query::read_command>>>>
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do_execute_base_query(
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query_processor& qp,
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std::vector<primary_key>&& primary_keys,
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service::query_state& state,
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const query_options& options,
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gc_clock::time_point now,
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lw_shared_ptr<const service::pager::paging_state> paging_state) const;
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future<shared_ptr<cql_transport::messages::result_message>>
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execute_base_query(
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query_processor& qp,
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std::vector<primary_key>&& primary_keys,
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service::query_state& state,
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const query_options& options,
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gc_clock::time_point now,
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lw_shared_ptr<const service::pager::paging_state> paging_state) const;
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virtual void update_stats_rows_read(int64_t rows_read) const override {
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_stats.rows_read += rows_read;
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_stats.secondary_index_rows_read += rows_read;
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}
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future<coordinator_result<::shared_ptr<cql_transport::messages::result_message::rows>>> read_posting_list(
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query_processor& qp,
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const query_options& options,
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uint64_t limit,
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service::query_state& state,
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gc_clock::time_point now,
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db::timeout_clock::time_point timeout,
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bool include_base_clustering_key) const;
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dht::partition_range_vector get_partition_ranges_for_local_index_posting_list(const query_options& options) const;
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dht::partition_range_vector get_partition_ranges_for_global_index_posting_list(const query_options& options) const;
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query::partition_slice get_partition_slice_for_local_index_posting_list(const query_options& options) const;
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query::partition_slice get_partition_slice_for_global_index_posting_list(const query_options& options) const;
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bytes compute_idx_token(const partition_key& key) const;
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};
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}
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}
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