On 30/05/17 09:46 AM, Per Jessen wrote:
What is the definition of "hash", by the way? Is it just an index, and the code still has to look at the original text file?
No, it's a table that is ready to load into memory and do lookups in. (Berkeley DB in postfix).
There seem to be a couple of ways of doing the "hash" indexing, that's certainly one of them.
From the man page:
texthash (read-only) Produces similar results as hash: files, except that you don't need to run the postmap(1) command before you can use the file, and that it does not detect changes after the file is read. dbm An indexed file type based on hashing. Available on systems with support for DBM data-bases. hash An indexed file type based on hashing. Available on systems with support for Berkeley DB databases. internal A non-shared, in-memory hash table. Its content are lost when a process terminates. There is also: lmdb OpenLDAP LMDB database (a memory-mapped, persistent file). available on systems with support for LMDB databases. This is described in lmdb_table(5). Hmm
From http://www.lmdb.tech/doc/ <quote> Lightning Memory-Mapped Database Manager (LMDB)
LMDB is a Btree-based database management library modeled loosely on the BerkeleyDB API, but much simplified. The entire database is exposed in a memory map, and all data fetches return data directly from the mapped memory, so no malloc's or memcpy's occur during data fetches. As such, the library is extremely simple because it requires no page caching layer of its own, and it is extremely high performance and memory-efficient. It is also fully transactional with full ACID semantics, and when the memory map is read-only, the database integrity cannot be corrupted by stray pointer writes from application code. </quote> Well, that looks impressive. Simple, fast. Can deal with extremely large datasets. The bottom line is that there are so many more robust alternatives to using a remote network accessed store such as MySQL, PostGRESS, NIS or LDAP for non-distributed systems that I can't see or justify their use other than as an intellectual exercise. If you want reliable operation and are actually concerned about speed in th sense that you want fast transactions, then use one of the above and buy a faster network connects. I think you'll still find that the limiting factor is the remote mail sources that fetchmail has to deal with. -- A: Yes. > Q: Are you sure? >> A: Because it reverses the logical flow of conversation. >>> Q: Why is top posting frowned upon? -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org