MySql——tables: Environment --- global_lsn

[Haohao966]

I want to know:
What does the field name global_lsn in the Environment table in the Mysql database mean
What data will be stored in the Environment table

[yhmo]

The global_lsn is for WAL(write ahead log) functionality.
The purpose of wal is to ensure data safety, such as insert/delete action.
Before data is serialize to disk(and record to meta service), WAL firstly store the data to local storage(under the /milvus/wal folder), if milvus crashed, the WAL can recovery the data at the next time milvus start.
So each insert/delete action has a id to WAL, we call it 'lsn'. Each collection has a latest lsn, recorded in meta system(in the Tables table). Latest lsn means the milvus has successfully consumed the insert/delete action which id equal the lsn.
For example, client invoke insert api 3 times, so there are 3 actions were recorded in WAL, their id is: 1000, 1001, 1002, 1003. Milvus successfully store the 1000/1001 action data into disk, but crashed at 1002. So the latest lsn of the collection is 1001, the global_lsn also is 1001. Then you restart milvus, the WAL will recovery the 1002 and 1003 actions.

Currently the Environment table only used to record global_lsn.

[Haohao966]

thank you very much

[yhmo]

If you set WAL to disable, the global_lsn will be always 0