1LMDB_TABLE(5) File Formats Manual LMDB_TABLE(5)
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6 lmdb_table - Postfix LMDB adapter
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9 postmap lmdb:/etc/postfix/filename
10 postmap -i lmdb:/etc/postfix/filename <inputfile
11 postmap -d "key" lmdb:/etc/postfix/filename
13 postmap -d - lmdb:/etc/postfix/filename <inputfile
14 postmap -q "key" lmdb:/etc/postfix/filename
16 postmap -q - lmdb:/etc/postfix/filename <inputfile
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19 The Postfix LMDB adapter provides access to a persistent, mem‐
20 ory-mapped, key-value store. The database size is limited only by the
21 size of the memory address space (typically 31 or 47 bits on 32-bit or
22 64-bit CPUs, respectively) and by the available file system space.
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25 The LMDB adapter supports all Postfix lookup table operations. This
26 makes LMDB suitable for Postfix address rewriting, routing, access
27 policies, caches, or any information that can be stored under a fixed
28 lookup key.
29 When a transaction fails due to a full database, Postfix resizes the
31 database and retries the transaction.
32 Postfix table lookups may generate partial search keys such as domain
34 names without one or more subdomains, network addresses without one or
35 more least-significant octets, or email addresses without the local‐
36 part, address extension or domain portion. This behavior is also found
37 with, for example, btree:, hash:, or ldap: tables.
38 Changes to an LMDB database do not trigger an automatic daemon restart,
40 and do not require a daemon restart with "postfix reload".
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43 LMDB's copy-on-write architecture provides safe updates, at the cost of
44 using more space than some other flat-file databases. Read operations
45 are memory-mapped for speed. Write operations are not memory-mapped to
46 avoid silent corruption due to stray pointer bugs.
47 Multiple processes can safely update an LMDB database without serializ‐
49 ing requests through the proxymap(8) service. This makes LMDB suitable
50 as a shared cache for verify(8) or postscreen(8) services.
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53 The Postfix LMDB adapter does not use LMDB's built-in locking scheme,
54 because that would require world-writable lockfiles and would violate
55 the Postfix security model. Instead, Postfix uses fcntl(2) locks with
56 whole-file granularity. Programs that use LMDB's built-in locking pro‐
57 tocol will corrupt a Postfix LMDB database or will read garbage.
58 Every Postfix LMDB database read or write transaction must be protected
60 from start to end with a shared or exclusive fcntl(2) lock. A writer
61 may atomically downgrade an exclusive lock to a shared lock, but it
62 must hold an exclusive lock while opening another write transaction.
63 Note that fcntl(2) locks do not protect transactions within the same
65 process against each other. If a program cannot avoid making simulta‐
66 neous database requests, then it must protect its transactions with
67 in-process locks, in addition to the per-process fcntl(2) locks.
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70 Short-lived programs automatically pick up changes to main.cf. With
71 long-running daemon programs, Use the command "postfix reload" after a
72 configuration change.
73 lmdb_map_size (16777216)
75 The initial OpenLDAP LMDB database size limit in bytes.
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78 postconf(1), Postfix supported lookup tables
79 postmap(1), Postfix lookup table maintenance
80 postconf(5), configuration parameters
81
83 Use "postconf readme_directory" or "postconf html_directory" to locate
84 this information.
85 DATABASE_README, Postfix lookup table overview
86 LMDB_README, Postfix OpenLDAP LMDB howto
87
89 The Secure Mailer license must be distributed with this software.
90
92 LMDB support was introduced with Postfix version 2.11.
93
95 Howard Chu
96 Symas Corporation
97 Wietse Venema
99 IBM T.J. Watson Research
100 P.O. Box 704
101 Yorktown Heights, NY 10598, USA
102 Wietse Venema
104 Google, Inc.
105 111 8th Avenue
106 New York, NY 10011, USA
107 LMDB_TABLE(5)