NAME

       memcached_replace - Storing and Replacing Data

SYNOPSIS

       #include <libmemcached/memcached.h>
              Compile and link with -lmemcached

       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)

       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)

       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)

       memcached_return_t   memcached_set_by_key(memcached_st    *ptr,    const    char    *group_key,    size_t
       group_key_length,  const  char  *key,  size_t  key_length, const char *value, size_t value_length, time_t
       expiration, uint32_t flags)

       memcached_return_t   memcached_add_by_key(memcached_st    *ptr,    const    char    *group_key,    size_t
       group_key_length,  const  char  *key,  size_t  key_length, const char *value, size_t value_length, time_t
       expiration, uint32_t flags)

       memcached_return_t   memcached_replace_by_key(memcached_st   *ptr,   const   char   *group_key,    size_t
       group_key_length,  const  char  *key,  size_t  key_length, const char *value, size_t value_length, time_t
       expiration, uint32_t flags)

DESCRIPTION

       memcached_set(), memcached_add(), and memcached_replace() are  all  used  to  store  information  on  the
       server.  All  methods  take  a key, and its length to store the object. Keys are currently limited to 250
       characters when using either a version of memcached(1) which is 1.4 or below,  or  when  using  the  text
       protocol.  You must supply both a value and a length. Optionally you store the object. Keys are currently
       limited to 250 characters by the memcached(1) server.  You  must  supply  both  a  value  and  a  length.
       Optionally  you may test an expiration time for the object and a 16 byte value (it is meant to be used as
       a bitmap). "flags" is a 4byte space that is stored alongside of the main value. Many sub  libraries  make
       use of this field, so in most cases users should avoid making use of it.

       memcached_set() will write an object to the server. If an object already exists it will overwrite what is
       in the server. If the object does not exist it will be written. If you are using  the  non-blocking  mode
       this function will always return true unless a network error occurs.

       memcached_replace()  replaces  an object on the server. If the object is not found on the server an error
       occurs.

       memcached_add() adds an object to the server. If the object is found  on  the  server  an  error  occurs,
       otherwise the value is stored.

       memcached_set_by_key(),  memcached_add_by_key(),  and  memcached_replace_by_key() methods all behave in a
       similar method as the non key methods. The difference is that they use their group_key parameter  to  map
       objects to particular servers.

       If you are looking for performance, memcached_set() with non-blocking IO is the fastest way to store data
       on the server.

       All of the above functions are tested with the MEMCACHED_BEHAVIOR_USE_UDP behavior enabled. However, when
       using  these  operations with this behavior on, there are limits to the size of the payload being sent to
       the server.  The reason for these limits is that the  Memcached  Server  does  not  allow  multi-datagram
       requests  and  the  current  server  implementation  sets  a datagram size to 1400 bytes. Due to protocol
       overhead, the actual limit of the user supplied data is less than 1400 bytes and depends on the  protocol
       in   use,   as   well   as  the  operation  being  executed.  When  running  with  the  binary  protocol,
       MEMCACHED_BEHAVIOR_BINARY_PROTOCOL, the size of the key,value, flags and expiry combined may  not  exceed
       1368  bytes. When running with the ASCII protocol, the exact limit fluctuates depending on which function
       is being executed and whether the function is a cas operation or not. For non-cas ASCII  set  operations,
       there  are  at  least  1335  bytes available to split among the key, key_prefix, and value; for cas ASCII
       operations there are at least 1318 bytes available to split among the key, key_prefix and value.  If  the
       total  size  of  the  command,  including overhead, exceeds 1400 bytes, a MEMCACHED_WRITE_FAILURE will be
       returned.

RETURN VALUE

       All methods return a value of type memcached_return_t.

       On success the value will be MEMCACHED_SUCCESS.  Use memcached_strerror() to translate this  value  to  a
       printable string.

       For  memcached_replace()  and memcached_add(), MEMCACHED_NOTSTORED is a legitimate error in the case of a
       collision.

SEE ALSO

       memcached(1)    libmemcached(3)    memcached_strerror(3)     memcached_prepend(3)     memcached_append(3)
       memcached_cas(3)