Vlog files use lots of disk space: Add option to set LSMOnly option when opening p dir

[purist180 (Zhao Lin)]

Thanks!

We upgrade from 20.11.0 to 20.11.3,
It do save a large disk space
but we encounter another problem,
You can see this

"func: type() "error in 20.11.03 or later

In my application we use type() function ( using GraphQL+-) to get node list of nodes. But in the new version I encountered a problem that I cannot query according to the node type. We have no problem with the same data in version 20.11.0, but this version has the problem of write amplification. After we upgraded to 20.11.3（which fix the wirte amplification）, we encountered the problem that some nodes could not be queried by node type. There are more than a dozen types of nodes in our applic…