#++ # NAME # lmdb_table 5 # SUMMARY # Postfix LMDB adapter # SYNOPSIS # \fBpostmap lmdb:/etc/postfix/\fIfilename\fR # .br # \fBpostmap -i lmdb:/etc/postfix/\fIfilename\fB <\fIinputfile\fR # # \fBpostmap -d "\fIkey\fB" lmdb:/etc/postfix/\fIfilename\fR # .br # \fBpostmap -d - lmdb:/etc/postfix/\fIfilename\fB <\fIinputfile\fR # # \fBpostmap -q "\fIkey\fB" lmdb:/etc/postfix/\fIfilename\fR # .br # \fBpostmap -q - lmdb:/etc/postfix/\fIfilename\fB <\fIinputfile\fR # DESCRIPTION # 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. # REQUESTS # .ad # .fi # 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 "\fBpostfix reload\fR". # RELIABILITY # .ad # .fi # 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 # curruption 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. # SYNCHRONIZATION # .ad # .fi # 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 acquire an exclusive # lock between updating the database and starting 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. # CONFIGURATION PARAMETERS # .ad # .fi # Short-lived programs automatically pick up changes to # main.cf. With long-running daemon programs, Use the command # "\fBpostfix reload\fR" after a configuration change. # .IP "\fBlmdb_map_size (default: 16777216)\fR" # The initial LMDB database size limit in bytes. # SEE ALSO # postconf(1), Postfix supported lookup tables # postmap(1), Postfix lookup table maintenance # postconf(5), configuration parameters # README FILES # .ad # .fi # Use "\fBpostconf readme_directory\fR" or # "\fBpostconf html_directory\fR" to locate this information. # .na # .nf # DATABASE_README, Postfix lookup table overview # LMDB_README, Postfix OpenLDAP LMDB howto # LICENSE # .ad # .fi # The Secure Mailer license must be distributed with this software. # HISTORY # LMDB support was introduced with Postfix version 2.11. # AUTHOR(S) # Howard Chu # Symas Corporation # # Wietse Venema # IBM T.J. Watson Research # P.O. Box 704 # Yorktown Heights, NY 10598, USA #--