lmdb_table - Postfix LMDB adapter
postmap -i lmdb:/etc/postfix/filename <inputfile
postmap -d "key" lmdb:/etc/postfix/filename
postmap -d - lmdb:/etc/postfix/filename <inputfile
postmap -q "key" lmdb:/etc/postfix/filename
postmap -q - lmdb:/etc/postfix/filename <inputfile
The Postfix LMDB adapter provides access to a persistent, memory-mapped,
key-value store. The database size is limited only by the size of the memory
address space (typically 31 or 47 bits on 32-bit or 64-bit CPUs, respectively)
and by the available file system space.
The LMDB adapter supports all Postfix lookup table operations. This makes LMDB
suitable for Postfix address rewriting, routing, access policies, caches, or
any information that can be stored under a fixed lookup key.
When a transaction fails due to a full database, Postfix resizes the database
and retries the transaction.
Postfix table lookups may generate partial search keys such as domain names
without one or more subdomains, network addresses without one or more
least-significant octets, or email addresses without the localpart, address
extension or domain portion. This behavior is also found with, for example,
btree:, hash:, or ldap: tables.
Unlike other flat-file Postfix databases, changes to an LMDB database do not
trigger automatic daemon program restart, and do not require " postfix
LMDB's copy-on-write architecture provides safe updates, at the cost of using
more space than some other flat-file databases. Read operations are
memory-mapped for speed. Write operations are not memory-mapped to avoid
silent corruption due to stray pointer bugs.
Multiple processes can safely update an LMDB database without serializing
requests through the proxymap(8) service. This makes LMDB suitable as a shared
cache for verify(8) or postscreen(8) services.
The Postfix LMDB adapter does not use LMDB's built-in locking scheme, because
that would require world-writable lockfiles and would violate the Postfix
security model. Instead, Postfix uses fcntl(2) locks with whole-file
granularity. Programs that use LMDB's built-in locking protocol will corrupt a
Postfix LMDB database or will read garbage.
Every Postfix LMDB database read or write transaction must be protected from
start to end with a shared or exclusive fcntl(2) lock. A writer may atomically
downgrade an exclusive lock to a shared lock, but it must hold an exclusive
lock while opening another write transaction.
Note that fcntl(2) locks do not protect transactions within the same process
against each other. If a program cannot avoid making simultaneous database
requests, then it must protect its transactions with in-process locks, in
addition to the per-process fcntl(2) locks.
Short-lived programs automatically pick up changes to main.cf. With long-running
daemon programs, Use the command " postfix reload
" after a
- lmdb_map_size (default: 16777216)
- The initial LMDB database size limit in bytes.
postconf(1), Postfix supported lookup tables
postmap(1), Postfix lookup table maintenance
postconf(5), configuration parameters
Use " postconf readme_directory
" or " postconf
" to locate this information.
DATABASE_README, Postfix lookup table overview
LMDB_README, Postfix OpenLDAP LMDB howto
The Secure Mailer license must be distributed with this software.
LMDB support was introduced with Postfix version 2.11.
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
111 8th Avenue
New York, NY 10011, USA