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 Unlike other flat-file Postfix databases, changes to an LMDB database
40 do not trigger automatic daemon program restart, and do not require
41 "postfix reload".
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44 LMDB's copy-on-write architecture provides safe updates, at the cost of
45 using more space than some other flat-file databases. Read operations
46 are memory-mapped for speed. Write operations are not memory-mapped to
47 avoid silent corruption due to stray pointer bugs.
48 Multiple processes can safely update an LMDB database without serializ‐
50 ing requests through the proxymap(8) service. This makes LMDB suitable
51 as a shared cache for verify(8) or postscreen(8) services.
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54 The Postfix LMDB adapter does not use LMDB's built-in locking scheme,
55 because that would require world-writable lockfiles and would violate
56 the Postfix security model. Instead, Postfix uses fcntl(2) locks with
57 whole-file granularity. Programs that use LMDB's built-in locking pro‐
58 tocol will corrupt a Postfix LMDB database or will read garbage.
59 Every Postfix LMDB database read or write transaction must be protected
61 from start to end with a shared or exclusive fcntl(2) lock. A writer
62 may atomically downgrade an exclusive lock to a shared lock, but it
63 must hold an exclusive lock while opening another write transaction.
64 Note that fcntl(2) locks do not protect transactions within the same
66 process against each other. If a program cannot avoid making simulta‐
67 neous database requests, then it must protect its transactions with
68 in-process locks, in addition to the per-process fcntl(2) locks.
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71 Short-lived programs automatically pick up changes to main.cf. With
72 long-running daemon programs, Use the command "postfix reload" after a
73 configuration change.
74 lmdb_map_size (default: 16777216)
76 The initial LMDB database size limit in bytes.
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79 postconf(1), Postfix supported lookup tables
80 postmap(1), Postfix lookup table maintenance
81 postconf(5), configuration parameters
82
84 Use "postconf readme_directory" or "postconf html_directory" to locate
85 this information.
86 DATABASE_README, Postfix lookup table overview
87 LMDB_README, Postfix OpenLDAP LMDB howto
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90 The Secure Mailer license must be distributed with this software.
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93 LMDB support was introduced with Postfix version 2.11.
94
96 Howard Chu
97 Symas Corporation
98 Wietse Venema
100 IBM T.J. Watson Research
101 P.O. Box 704
102 Yorktown Heights, NY 10598, USA
103 Wietse Venema
105 Google, Inc.
106 111 8th Avenue
107 New York, NY 10011, USA
108 LMDB_TABLE(5)