git.m6w6.name Git - awesomized/libmemcached/blob - docs/memcached_set.rst

   1 ==========================
   2 Storing and Replacing Data
   3 ==========================
   4
   5
   6 Store value on server
   7
   8
   9 -------
  10 LIBRARY
  11 -------
  12
  13
  14 C Client Library for memcached (libmemcached, -lmemcached)
  15
  16
  17 --------
  18 SYNOPSIS
  19 --------
  20
  21
  22
  23 .. code-block:: perl
  24
  25    #include <libmemcached/memcached.h>
  26
  27    memcached_return_t
  28      memcached_set (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_t
  35      memcached_add (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_t
  42      memcached_replace (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
  48    memcached_return_t
  49      memcached_prepend(memcached_st *ptr,
  50                        const char *key, size_t key_length,
  51                        const char *value, size_t value_length,
  52                        time_t expiration,
  53                        uint32_t flags)
  54
  55    memcached_return_t
  56      memcached_append(memcached_st *ptr,
  57                       const char *key, size_t key_length,
  58                        const char *value, size_t value_length,
  59                        time_t expiration,
  60                        uint32_t flags)
  61    memcached_return_t
  62      memcached_cas(memcached_st *ptr,
  63                    const char *key, size_t key_length,
  64                    const char *value, size_t value_length,
  65                    time_t expiration,
  66                    uint32_t flags,
  67                    uint64_t cas);
  68
  69    memcached_return_t
  70      memcached_set_by_key(memcached_st *ptr,
  71                           const char *master_key, size_t master_key_length,
  72                           const char *key, size_t key_length,
  73                           const char *value, size_t value_length,
  74                           time_t expiration,
  75                           uint32_t flags);
  76
  77    memcached_return_t
  78      memcached_add_by_key(memcached_st *ptr,
  79                           const char *master_key, size_t master_key_length,
  80                           const char *key, size_t key_length,
  81                           const char *value, size_t value_length,
  82                           time_t expiration,
  83                           uint32_t flags);
  84
  85    memcached_return_t
  86      memcached_replace_by_key(memcached_st *ptr,
  87                               const char *master_key, size_t master_key_length,
  88                               const char *key, size_t key_length,
  89                               const char *value, size_t value_length,
  90                               time_t expiration,
  91                               uint32_t flags);
  92
  93    memcached_return_t
  94      memcached_prepend_by_key(memcached_st *ptr,
  95                               const char *master_key, size_t master_key_length,
  96                               const char *key, size_t key_length,
  97                               const char *value, size_t value_length,
  98                               time_t expiration,
  99                               uint32_t flags);
 100
 101    memcached_return_t
 102      memcached_append_by_key(memcached_st *ptr,
 103                              const char *master_key, size_t master_key_length,
 104                              const char *key, size_t key_length,
 105                              const char *value, size_t value_length,
 106                              time_t expiration,
 107                              uint32_t flags);
 108
 109    memcached_return_t
 110      memcached_cas_by_key(memcached_st *ptr,
 111                           const char *master_key, size_t master_key_length,
 112                           const char *key, size_t key_length,
 113                           const char *value, size_t value_length,
 114                           time_t expiration,
 115                           uint32_t flags,
 116                           uint64_t cas);
 117
 118
 119
 120 -----------
 121 DESCRIPTION
 122 -----------
 123
 124
 125 memcached_set(), memcached_add(), and memcached_replace() are all used to
 126 store information on the server. All methods take a key, and its length to
 127 store the object. Keys are currently limited to 250 characters by the
 128 memcached(1) server. You must also supply a value and a length. Optionally you
 129 may support an expiration time for the object and a 16 byte value (it is
 130 meant to be used as a bitmap).
 131
 132 memcached_set() will write an object to the server. If an object already
 133 exists it will overwrite what is in the server. If the object does not exist
 134 it will be written. If you are using the non-blocking mode this function
 135 will always return true unless a network error occurs.
 136
 137 memcached_replace() replaces an object on the server. If the object is not
 138 found on the server an error occurs.
 139
 140 memcached_add() adds an object to the server. If the object is found on the
 141 server an error occurs, otherwise the value is stored.
 142
 143 memcached_prepend() places a segment of data before the last piece of data
 144 stored. Currently expiration and key are not used in the server.
 145
 146 memcached_append() places a segment of data at the end of the last piece of
 147 data stored. Currently expiration and key are not used in the server.
 148
 149 memcached_cas() overwrites data in the server as long as the "cas" value is
 150 still the same in the server. You can get the cas value of a result by
 151 calling memcached_result_cas() on a memcached_result_st(3) structure. At the point
 152 that this note was written cas is still buggy in memached. Turning on support
 153 for it in libmemcached(3) is optional. Please see memcached_set() for
 154 information on how to do this.
 155
 156 memcached_set_by_key(), memcached_add_by_key(), memcached_replace_by_key(),
 157 memcached_prepend_by_key(), memcached_append_by_key_by_key(),
 158 memcached_cas_by_key() methods all behave in a similar method as the non key
 159 methods. The difference is that they use their master_key parameter to map
 160 objects to particular servers.
 161
 162 If you are looking for performance, memcached_set() with non-blocking IO is
 163 the fastest way to store data on the server.
 164
 165 All of the above functions are supported with the \ ``MEMCACHED_BEHAVIOR_USE_UDP``\
 166 behavior enabled. But when using these operations with this behavior on, there
 167 are limits to the size of the payload being sent to the server.  The reason for
 168 these limits is that the Memcahed Server does not allow multi-datagram requests
 169 and the current server implementation sets a datagram size to 1400 bytes. Due
 170 to protocol overhead, the actual limit of the user supplied data is less than
 171 1400 bytes and depends on the protocol in use as well as the operation being
 172 executed. When running with the binary protocol, \ `` MEMCACHED_BEHAVIOR_BINARY_PROTOCOL``\ ,
 173 the size of the key,value, flags and expiry combined may not exceed 1368 bytes.
 174 When running with the ASCII protocol, the exact limit fluctuates depending on
 175 which function is being executed and whether the function is a cas operation
 176 or not. For non-cas ASCII set operations, there are at least 1335 bytes available
 177 to split among the key, key_prefix, and value; for cas ASCII operations there are
 178 at least 1318 bytes available to split among the key, key_prefix and value. If the
 179 total size of the command, including overhead, exceeds 1400 bytes, a \ ``MEMCACHED_WRITE_FAILURE``\
 180 will be returned.
 181
 182
 183 ------
 184 RETURN
 185 ------
 186
 187
 188 All methods return a value of type \ ``memcached_return_t``\ .
 189 On success the value will be \ ``MEMCACHED_SUCCESS``\ .
 190 Use memcached_strerror() to translate this value to a printable string.
 191
 192 For memcached_replace() and memcached_add(), \ ``MEMCACHED_NOTSTORED``\  is a
 193 legitmate error in the case of a collision.
 194
 195
 196 ----
 197 HOME
 198 ----
 199
 200
 201 To find out more information please check:
 202 `https://launchpad.net/libmemcached <https://launchpad.net/libmemcached>`_
 203
 204
 205 --------
 206 SEE ALSO
 207 --------
 208
 209
 210 memcached(1) libmemached(3) memcached_strerror(3)
 211