leveldb 是一个 K-V 存储引擎，因此 Key 的设计就非常重要的了。 * 一方面需要保存用户自己的 User Key，另一方面还需要有一个序列号来标识同一个 Key 的多个版本更新。 * * 在 InnoDB 中，为了支持 MVCC 所以 InnoDB 直接将 Transaction

ParsedInternalKey 实际上就是 Internal Key 拆解之后的产物 */

A comparator for internal keys that uses a specified comparator for the user key portion and breaks ties by decreasing sequence number.

BlockHandle is a pointer to the extent of a file that stores a data block or a meta block.

Bloom Filter */

DB contents are stored in a set of blocks, each of which holds a sequence of key,value pairs. Each block may be compressed before being stored in a f

We want to make sure that with a single writer and multiple concurrent readers (with no synchronization other than when a reader's iterator is created

Helper class for tests to unify the interface between BlockBuilder/TableBuilder and Block/Table.

Notified when log reader encounters corruption.

Information kept for every waiting writer

Memtables and sstables that make the DB representation contain (userkey,seq,type) => uservalue entries. DBIter combines multiple entries for the same

A helper for the POSIX Env to facilitate testing.

A helper for the Windows Env to facilitate testing.

A wrapper that allows injection of errors.