3 ms·

To be honest I am not entirely sure of my interpretation of the issue yet. What I know is that on those devices you sometimes can't read your writes with LMDB i

by catwell 11y ago

To be honest I am not entirely sure of my interpretation of the issue yet. What I know is that on those devices you sometimes can't read your writes with LMDB if it's not using MDB_WRITEMAP. While trying to debug I ended up on the only question ever asked by Howard Chu (LMDB author) on Stack Overflow: http://stackoverflow.com/questions/7061910/when-does-an-o-sync-write-become-visible-in-the-pagecache-mmapd-file http://stackoverflow.com/questions/7061910/when-does-an-o-sy... I am still trying to figure out what exactly is happening here but it's not very easy given that I do not even have access to a rooted phone that exhibits the issue.

hyc_symas 11y ago
It really depends on where you're storing your DB files. If you're using the /data partition it should Just Work. If you're using external storage, yes, android does a bunch of stupid tricks to implement its secure storage, and that interferes with mmap. Here's the code that resulted from that Stack Overflow question: https://github.com/LMDB/lmdb/blob/mdb.master/libraries/liblmdb/mdb.c#L4091-L4096 https://github.com/LMDB/lmdb/blob/mdb.master/libraries/liblm... After 36 years of writing code, I have more answers than questions.