mirror of https://github.com/facebook/rocksdb.git
51 lines
2.2 KiB
C++
51 lines
2.2 KiB
C++
// 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 "stackable_db.h"
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namespace rocksdb {
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// This class contains APIs to open rocksdb with specific support eg. TTL
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class UtilityDB {
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public:
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// Open the database with TTL support.
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//
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// USE-CASES:
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// This API should be used to open the db when key-values inserted are
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// meant to be removed from the db in a non-strict 'ttl' amount of time
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// Therefore, this guarantees that key-values inserted will remain in the
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// db for >= ttl amount of time and the db will make efforts to remove the
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// key-values as soon as possible after ttl seconds of their insertion.
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//
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// BEHAVIOUR:
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// TTL is accepted in seconds
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// (int32_t)Timestamp(creation) is suffixed to values in Put internally
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// Expired TTL values deleted in compaction only:(Timestamp+ttl<time_now)
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// Get/Iterator may return expired entries(compaction not run on them yet)
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// Different TTL may be used during different Opens
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// Example: Open1 at t=0 with ttl=4 and insert k1,k2, close at t=2
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// Open2 at t=3 with ttl=5. Now k1,k2 should be deleted at t>=5
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// read_only=true opens in the usual read-only mode. Compactions will not be
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// triggered(neither manual nor automatic), so no expired entries removed
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//
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// CONSTRAINTS:
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// Not specifying/passing or non-positive TTL behaves like TTL = infinity
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//
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// !!!WARNING!!!:
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// Calling DB::Open directly to re-open a db created by this API will get
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// corrupt values(timestamp suffixed) and no ttl effect will be there
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// during the second Open, so use this API consistently to open the db
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// Be careful when passing ttl with a small positive value because the
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// whole database may be deleted in a small amount of time
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static Status OpenTtlDB(const Options& options,
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const std::string& name,
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StackableDB** dbptr,
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int32_t ttl = 0,
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bool read_only = false);
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};
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} // namespace rocksdb
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