fork of https://github.com/oxigraph/rocksdb and https://github.com/facebook/rocksdb for nextgraph and oxigraph
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77 lines
3.1 KiB
77 lines
3.1 KiB
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#pragma once
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#include <memory>
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namespace rocksdb {
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class Iterator;
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struct ParsedInternalKey;
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class Slice;
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class Arena;
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struct ReadOptions;
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struct TableProperties;
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class GetContext;
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// A Table is a sorted map from strings to strings. Tables are
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// immutable and persistent. A Table may be safely accessed from
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// multiple threads without external synchronization.
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class TableReader {
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public:
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virtual ~TableReader() {}
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// Returns a new iterator over the table contents.
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// The result of NewIterator() is initially invalid (caller must
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// call one of the Seek methods on the iterator before using it).
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// arena: If not null, the arena needs to be used to allocate the Iterator.
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// When destroying the iterator, the caller will not call "delete"
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// but Iterator::~Iterator() directly. The destructor needs to destroy
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// all the states but those allocated in arena.
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virtual Iterator* NewIterator(const ReadOptions&, Arena* arena = nullptr) = 0;
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// Given a key, return an approximate byte offset in the file where
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// the data for that key begins (or would begin if the key were
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// present in the file). The returned value is in terms of file
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// bytes, and so includes effects like compression of the underlying data.
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// E.g., the approximate offset of the last key in the table will
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// be close to the file length.
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virtual uint64_t ApproximateOffsetOf(const Slice& key) = 0;
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// Set up the table for Compaction. Might change some parameters with
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// posix_fadvise
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virtual void SetupForCompaction() = 0;
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virtual std::shared_ptr<const TableProperties> GetTableProperties() const = 0;
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// Prepare work that can be done before the real Get()
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virtual void Prepare(const Slice& target) {}
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// Report an approximation of how much memory has been used.
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virtual size_t ApproximateMemoryUsage() const = 0;
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// Calls get_context->SaveValue() repeatedly, starting with
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// the entry found after a call to Seek(key), until it returns false.
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// May not make such a call if filter policy says that key is not present.
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//
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// get_context->MarkKeyMayExist needs to be called when it is configured to be
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// memory only and the key is not found in the block cache.
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//
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// readOptions is the options for the read
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// key is the key to search for
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virtual Status Get(const ReadOptions& readOptions, const Slice& key,
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GetContext* get_context) = 0;
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// convert db file to a human readable form
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virtual Status DumpTable(WritableFile* out_file) {
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return Status::NotSupported("DumpTable() not supported");
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}
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};
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} // namespace rocksdb
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