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[m6w6/libmemcached] / docs / memcached_set.pod
1 =head1 NAME
2
3 memcached_set, memcached_add, memcached_replace - Store value on server
4
5 =head1 LIBRARY
6
7 C Client Library for memcached (libmemcached, -lmemcached)
8
9 =head1 SYNOPSIS
10
11 #include <memcached.h>
12
13 memcached_return
14 memcached_set (memcached_st *ptr,
15 const char *key, size_t key_length,
16 const char *value, size_t value_length,
17 time_t expiration,
18 uint32_t flags);
19
20 memcached_return
21 memcached_add (memcached_st *ptr,
22 const char *key, size_t key_length,
23 const char *value, size_t value_length,
24 time_t expiration,
25 uint32_t flags);
26
27 memcached_return
28 memcached_replace (memcached_st *ptr,
29 const char *key, size_t key_length,
30 const char *value, size_t value_length,
31 time_t expiration,
32 uint32_t flags);
33
34 memcached_return
35 memcached_prepend(memcached_st *ptr,
36 const char *key, size_t key_length,
37 const char *value, size_t value_length,
38 time_t expiration,
39 uint32_t flags)
40
41 memcached_return
42 memcached_append(memcached_st *ptr,
43 const char *key, size_t key_length,
44 const char *value, size_t value_length,
45 time_t expiration,
46 uint32_t flags)
47 memcached_return
48 memcached_cas(memcached_st *ptr,
49 const char *key, size_t key_length,
50 const char *value, size_t value_length,
51 time_t expiration,
52 uint32_t flags,
53 uint64_t cas);
54
55 memcached_return
56 memcached_set_by_key(memcached_st *ptr,
57 const char *master_key, size_t master_key_length,
58 const char *key, size_t key_length,
59 const char *value, size_t value_length,
60 time_t expiration,
61 uint32_t flags);
62
63 memcached_return
64 memcached_add_by_key(memcached_st *ptr,
65 const char *master_key, size_t master_key_length,
66 const char *key, size_t key_length,
67 const char *value, size_t value_length,
68 time_t expiration,
69 uint32_t flags);
70
71 memcached_return
72 memcached_replace_by_key(memcached_st *ptr,
73 const char *master_key, size_t master_key_length,
74 const char *key, size_t key_length,
75 const char *value, size_t value_length,
76 time_t expiration,
77 uint32_t flags);
78
79 memcached_return
80 memcached_prepend_by_key(memcached_st *ptr,
81 const char *master_key, size_t master_key_length,
82 const char *key, size_t key_length,
83 const char *value, size_t value_length,
84 time_t expiration,
85 uint32_t flags);
86
87 memcached_return
88 memcached_append_by_key(memcached_st *ptr,
89 const char *master_key, size_t master_key_length,
90 const char *key, size_t key_length,
91 const char *value, size_t value_length,
92 time_t expiration,
93 uint32_t flags);
94
95 memcached_return
96 memcached_cas_by_key(memcached_st *ptr,
97 const char *master_key, size_t master_key_length,
98 const char *key, size_t key_length,
99 const char *value, size_t value_length,
100 time_t expiration,
101 uint32_t flags,
102 uint64_t cas);
103
104 =head1 DESCRIPTION
105
106 memcached_set(), memcached_add(), and memcached_replace() are all used to
107 store information on the server. All methods take a key, and its length to
108 store the object. Keys are currently limited to 250 characters by the
109 memcached(1) server. You must also supply a value and a length. Optionally you
110 may support an expiration time for the object and a 16 byte value (it is
111 meant to be used as a bitmap).
112
113 memcached_set() will write an object to the server. If an object already
114 exists it will overwrite what is in the server. If the object does not exist
115 it will be written. If you are using the non-blocking mode this function
116 will always return true unless a network error occurs.
117
118 memcached_replace() replaces an object on the server. If the object is not
119 found on the server an error occurs.
120
121 memcached_add() adds an object to the server. If the object is found on the
122 server an error occurs, otherwise the value is stored.
123
124 memcached_prepend() places a segment of data before the last piece of data
125 stored. Currently expiration and key are not used in the server.
126
127 memcached_append() places a segment of data at the end of the last piece of
128 data stored. Currently expiration and key are not used in the server.
129
130 memcached_cas() overwrites data in the server as long as the "cas" value is
131 still the same in the server. You can get the cas value of a result by
132 calling memcached_result_cas() on a memcached_result_st(3) structure. At the point
133 that this note was written cas is still buggy in memached. Turning on support
134 for it in libmemcached(3) is optional. Please see memcached_set() for
135 information on how to do this.
136
137 memcached_set_by_key(), memcached_add_by_key(), memcached_replace_by_key(),
138 memcached_prepend_by_key(), memcached_append_by_key_by_key(),
139 memcached_cas_by_key() methods all behave in a similar method as the non key
140 methods. The difference is that they use their master_key parameter to map
141 objects to particular servers.
142
143 If you are looking for performance, memcached_set() with non-blocking IO is
144 the fastest way to store data on the server.
145
146 All of the above functions are supported with the C<MEMCACHED_BEHAVIOR_USE_UDP>
147 behavior enabled. But when using these operations with this behavior on, there
148 are limits to the size of the payload being sent to the server. The reason for
149 these limits is that the Memcahed Server does not allow multi-datagram requests
150 and the current server implementation sets a datagram size to 1400 bytes. Due
151 to protocol overhead, the actual limit of the user supplied data is less than
152 1400 bytes and depends on the protocol in use as well as the operation being
153 executed. When running with the binary protocol, C< MEMCACHED_BEHAVIOR_BINARY_PROTOCOL>,
154 the size of the key,value, flags and expiry combined may not exceed 1368 bytes.
155 When running with the ASCII protocol, the exact limit fluctuates depending on
156 which function is being executed and whether the function is a cas operation
157 or not. For non-cas ASCII set operations, there are at least 1335 bytes available
158 to split among the key, key_prefix, and value; for cas ASCII operations there are
159 at least 1318 bytes available to split among the key, key_prefix and value. If the
160 total size of the command, including overhead, exceeds 1400 bytes, a C<MEMCACHED_WRITE_FAILURE>
161 will be returned.
162
163
164 =head1 RETURN
165
166 All methods return a value of type C<memcached_return>.
167 On success the value will be C<MEMCACHED_SUCCESS>.
168 Use memcached_strerror() to translate this value to a printable string.
169
170 For memcached_replace() and memcached_add(), C<MEMCACHED_NOTSTORED> is a
171 legitmate error in the case of a collision.
172
173 =head1 HOME
174
175 To find out more information please check:
176 L<http://tangent.org/552/libmemcached.html>
177
178 =head1 AUTHOR
179
180 Brian Aker, E<lt>brian@tangent.orgE<gt>
181
182 =head1 SEE ALSO
183
184 memcached(1) libmemached(3) memcached_strerror(3)
185
186 =cut
187