东京内阁：.tcb.wal文件与.tcb文件一起创建。 删除记录时，db大小不会减小

Question

I am using tokyo cabinets B+ tree API to create a lookup database. On linux environment I see a .tcb.wal file created along with the actual .tcb database file. The size of this file is 0. I wonder whether its a lock file that is created to help synchronization. Also when I delete records from the database the size of the file does not decrease. Any reasons why its behaving like that?

Answer 1

The extension .wal stands for Write Ahead Logging file. This file is only relevant if you use any transaction functions; most applications do not use these. (For details, search for "ahead" in the documentation.)

The file size does not change for every deletion for efficiency reasons. Similarly, if you create an empty database, it will reserve space for faster insertions.