c83a84e98c
Summary: The `creation_time` table property has long stored the file's oldest ancestor time (the oldest key time among the file's ancestors, falling back to flush/compaction time), not the file's creation time, which is `file_creation_time`. A TODO in table_properties.h acknowledged the misleading name. This change starts the API migration: `TableProperties::oldest_ancestor_time` is the new name, and `creation_time` remains as a deprecated alias sharing storage via an anonymous union, so existing external reads and writes continue to compile and behave identically. An anonymous union is used rather than a `uint64_t&` alias member. A reference member would delete TableProperties copy/move assignment, make the implicit copy constructor bind the copy's alias to the source object (dangling), permit writes through a const TableProperties, add 8 bytes, and break the uint64_t-range walk in TEST_SetRandomTableProperties. The union leaves size, layout, copying, constness, and offsetof unchanged. Reading the other union member is formally UB in ISO C++, but both members are uint64_t and this is supported in practice by GCC, Clang, and MSVC. All in-repo uses of the old name now use `oldest_ancestor_time`. Names that are externally observable or persisted are intentionally unchanged: * On-disk property name `rocksdb.creation.time` (`TablePropertiesNames::kCreationTime`) * The `"creation_time"` key in TableProperties serialization (used by remote compaction) * The event-log JSON key and `TableProperties::ToString()` label * Java `TableProperties.getCreationTime()` and C `rocksdb_table_properties_creation_time()` C API: the auto-binding generator (tools/c_api_gen/auto_simple_bindings.py) only considered direct FieldDecls and failed on the anonymous union's implicit unnamed field. It now treats anonymous union members as direct fields. Regenerating adds a new C getter `rocksdb_table_properties_oldest_ancestor_time()` alongside the existing `rocksdb_table_properties_creation_time()`. Follow-up: remove the deprecated `creation_time` alias in a future release. Pull Request resolved: https://github.com/facebook/rocksdb/pull/15304 Test Plan: New unit test DBTablePropertiesTest.CreationTimeAliasesOldestAncestorTime verifies the two names share an address and that a write through the old name is visible through the new one. options_settable_test and compaction_service_test cover TableProperties serialization round trips through the unchanged "creation_time" key, now mapped to the renamed field. Reviewed By: jaykorean Differential Revision: D123079083 Pulled By: pdillinger fbshipit-source-id: 18b07d91f303a8f6de58da0c730f80d8c371505c
RocksDB: A Persistent Key-Value Store for Flash and RAM Storage
RocksDB is developed and maintained by Facebook Database Engineering Team. It is built on earlier work on LevelDB by Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)
This code is a library that forms the core building block for a fast key-value server, especially suited for storing data on flash drives. It has a Log-Structured-Merge-Database (LSM) design with flexible tradeoffs between Write-Amplification-Factor (WAF), Read-Amplification-Factor (RAF) and Space-Amplification-Factor (SAF). It has multi-threaded compactions, making it especially suitable for storing multiple terabytes of data in a single database.
Start with example usage here: https://github.com/facebook/rocksdb/tree/main/examples
See the github wiki for more explanation.
The public interface is in include/. Callers should not include or
rely on the details of any other header files in this package. Those
internal APIs may be changed without warning.
Questions and discussions are welcome on the RocksDB Developers Public Facebook group and email list on Google Groups.
License
RocksDB is dual-licensed under both the GPLv2 (found in the COPYING file in the root directory) and Apache 2.0 License (found in the LICENSE.Apache file in the root directory). You may select, at your option, one of the above-listed licenses.