git.m6w6.name Git - m6w6/libmemcached/blob - 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