mirror of
https://github.com/matrix-construct/construct
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92 lines
3.4 KiB
C++
92 lines
3.4 KiB
C++
// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#pragma once
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#define HAVE_IRCD_DB_DATABASE_DESCRIPTOR_H
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namespace ircd::db
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{
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struct descriptor;
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using description = std::vector<descriptor>;
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}
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/// Descriptor of a column when opening database. Database must be opened with
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/// a consistent set of descriptors describing what will be found upon opening.
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struct ircd::db::descriptor
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{
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using typing = std::pair<std::type_index, std::type_index>;
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/// User given name for this column. Must be consistent.
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std::string name;
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/// User given description of this column; not used by RocksDB
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std::string explain;
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/// Indicate key and value type.
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typing type { typeid(string_view), typeid(string_view) };
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/// RocksDB ColumnFamilyOptions string; can be used for items not
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/// otherwise specified here.
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std::string options {};
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/// User given comparator. We can automatically set this value for
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/// some types given for the type.first typeid; otherwise it must be
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/// set for exotic/unsupported keys.
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db::comparator cmp {};
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/// User given prefix extractor.
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db::prefix_transform prefix {};
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/// Indicates if this column should be marked for deletion. Users who
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/// upgrade to the new schema will still require a legacy descriptor
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/// with most of the essential fields preceding this value to open db.
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///
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/// !!! Setting this to true deletes all data for this column !!!
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bool drop { false };
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/// Size of the LRU cache for uncompressed blocks
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ssize_t cache_size { -1 };
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/// Size of the LRU cache for compressed blocks
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ssize_t cache_size_comp { -1 };
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/// Bloom filter bits. Filter is still useful even if queries are expected
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/// to always hit on this column; see `expect_queries_hit` option.
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size_t bloom_bits { 10 };
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/// Set this option to true if queries to this column are expected to
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/// find keys that exist. This is useful for columns with keys that
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/// were first found from values in another column, where if the first
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/// column missed there'd be no reason to query this column.
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bool expect_queries_hit { false };
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/// Data block size for uncompressed data. Compression will make the
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/// block smaller when it IO's to and from disk. Smaller blocks may be
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/// more space and query overhead if values exceed this size. Larger
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/// blocks will read and cache unrelated data if values are smaller
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/// than this size.
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size_t block_size { 512 };
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/// Data block size for metadata blocks. Other configuration which may
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/// not yet be in this descriptor affects the best choice of this param;
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/// generally these blocks are preloaded on DB open. They can also
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/// participate in the block cache. At the time this comment was written
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/// top-level metadata blocks are preloaded and leaf blocks are put in
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/// the cache.
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size_t meta_block_size { 512 };
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/// Compression algorithm for this column. Empty string is equal to
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/// kNoCompression. List is semicolon separated to allow fallbacks in
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/// case the first algorithms are not supported.
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std::string compression {"kLZ4Compression;kSnappyCompression"};
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/// User given compaction callback surface.
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db::compactor compactor {};
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};
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