Rr snapshot #1510
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Rr snapshot #1510
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…ference This is a second batch of cleanups from the repeatable read snapshot work. - Make rdb_get_rocksdb_db return reference instead of pointer, update callers and callees. Inline this function in ha_rocksdb_proto.h, move rdb declaration there to support inlining in detail namespace as documentation that it should not be accessed directly. Update ha_rocksdb.cc itself to use rdb_get_rocksdb_db instead of rdb. Remove many redudant rdb != nullptr checks and asserts. - Introduce rdb_snapshot_unique_ptr with a custom deleter and a factory function get_rdb_snapshot to manager global RocksDB snapshots - Make Rdb_explicit_snapshot create the snapshot itself, by calling get_rdb_snapshot, instead of receiving one through parameters, simplify its signature. - Replace rocksdb::ManagedSnapshot uses with rdb_snapshot_unique_ptr ones. - Remove rarely-used explicit transaction snapshot assignment code from acquire_snapshot and move it to the few callers where it may happen. Add new method Rdb_transaction::has_explicit_or_read_only_snapshot to support this. - For Rdb_transaction, make m_insert_count, m_update_count, m_delete_count, m_auto_incr_map, & m_rollback_only fields private instead of protected. Move their reset at the end of committed or rolledback transactions to on_finish method in the base class. Remove redundant m_writes_at_last_savepoint reset in set_initial_savepoint. - Add several asserts.
Make MyRocks isolation behavior closer to that of InnoDB: - All data-writing SQL statements, and read statements under READ COMMITTED isolation level take a RocksDB snapshot at the beginning of the statement, and release it at the end. - Data-reading SQL statements under REPEATABLE READ share a RocksDB snapshot which is acquired on a first such statement and released at the end of a transaction. The above causes other user-visible changes: - rocksdb_skip_snapshot_validation system variable becomes a no-op. This variable should be removed at a later time. - SHOW ENGINE ROCKSDB STATUS output is extended with RR read snapshot information. Implementation details: - Introduce new possible value for Rdb_transaction::statement_snapshot_type: snapshot_type::RR, set iff performing a read under RR. - Introduce Rdb_transaction::end_stmt method, to be called at the end of each MyRocks-involving SQL statement in a transaction, and virtual method release_stmt_snapshot with implementation for both regular and WB transactions. - Unify existing code to restore an older RocksDB snapshot if a statement failed, as well as the code to release snapshots at the end of RC statements.
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Creating a draft PR because it contains a prerequisite commits, which is PR'ed separately. Will be rebased after the prerequisite is merged |
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