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

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