4fa12f2fb8
The header sits in many other headers, but there's a handy schema_fwd.hh that's tiny and contains needed declarations for other headers. So replace shema.hh with schema_fwd.hh in most of the headers (and remove completely from some). Signed-off-by: Pavel Emelyanov <xemul@scylladb.com> Message-Id: <20200303102050.18462-1-xemul@scylladb.com>
72 lines
3.0 KiB
C++
72 lines
3.0 KiB
C++
/*
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* Copyright (C) 2018 ScyllaDB
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Scylla is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include "database_fwd.hh"
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#include "schema_fwd.hh"
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#include "mutation_query.hh"
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#include "cache_temperature.hh"
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#include <seastar/core/distributed.hh>
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/// Run the mutation query on all shards.
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///
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/// Under the hood it uses a multishard_combining_reader for reading the
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/// range(s) from all shards.
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///
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/// The query uses paging. The read will stop after reaching one of the page
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/// size limits. Page size is determined by the read_command (row and partition
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/// limits) and by the max_size parameter (max memory size of results).
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///
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/// Optionally the query can be stateful. This means that after filling the
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/// page, the shard readers are saved in the `querier_cache` on their home shard
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/// (wrapped in a `shard_mutation_querier`). Fragments already read from
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/// the shard readers, but not consumed by the results builder (due to
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/// reaching the limit), are extracted from the `multishard_combining_reader`'s
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/// (and the foreign readers wrapping the shard readers) buffers and pushed back
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/// into the shard reader they originated from. This way only the shard readers
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/// have to be cached in order to continue the query.
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/// When reading the next page these querier objects are looked up from
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/// their respective shard's `querier_cache`, instead of creating new shard
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/// readers.
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/// To enable stateful queries set the `query_uuid` field of the read command
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/// to an id unique to the query. This can be easily achived by generating a
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/// random uuid with `utils::make_random_uuid()`.
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/// It is advisable that the `is_first_page` flag of the read command is set on
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/// the first page of the query so that a pointless lookup is avoided.
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///
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/// Note: params passed by reference are expected to be kept alive by the caller
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/// for the duration of the query. Params passed by const reference are expected
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/// to *not* change during the query, as they will possibly be accessed from
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/// other shards.
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///
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/// \see multishard_combined_reader
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/// \see querier_cache
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future<std::tuple<foreign_ptr<lw_shared_ptr<reconcilable_result>>, cache_temperature>> query_mutations_on_all_shards(
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distributed<database>& db,
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schema_ptr s,
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const query::read_command& cmd,
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const dht::partition_range_vector& ranges,
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tracing::trace_state_ptr trace_state,
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uint64_t max_size,
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db::timeout_clock::time_point timeout);
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