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33 lines
1.3 KiB
C++
33 lines
1.3 KiB
C++
#pragma once
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#include <Common/Priority.h>
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namespace DB
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{
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/// Indices and priorities of `AsyncLoader` pools.
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/// The most important difference from regular ThreadPools is priorities of pools:
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/// * Pools that have different priorities do NOT run jobs simultaneously (with small exception due to dynamic prioritization).
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/// * Pools with lower priority wait for all jobs in higher priority pools to be done.
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/// Note that pools also have different configurable sizes not listed here. See `Context::getAsyncLoader()` for details.
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/// WARNING: `*PoolId` values must be unique and sequential w/o gaps.
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/// Used for executing load jobs that are waited for by queries or in case of synchronous table loading.
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constexpr size_t TablesLoaderForegroundPoolId = 0;
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constexpr Priority TablesLoaderForegroundPriority{0};
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/// Has lower priority and is used by table load jobs.
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constexpr size_t TablesLoaderBackgroundLoadPoolId = 1;
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constexpr Priority TablesLoaderBackgroundLoadPriority{1};
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/// Has even lower priority and is used by startup jobs.
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/// NOTE: This pool is required to begin table startup only after all tables are loaded.
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/// NOTE: Which is needed to prevent heavy merges/mutations from consuming all the resources, slowing table loading down.
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constexpr size_t TablesLoaderBackgroundStartupPoolId = 2;
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constexpr Priority TablesLoaderBackgroundStartupPriority{2};
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}
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