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MEMCACHED_ADD_BY_KEY(3)		 libmemcached	       MEMCACHED_ADD_BY_KEY(3)

NAME
       memcached_add_by_key - Storing and Replacing Data

SYNOPSIS
       #include	<libmemcached/memcached.h>

       memcached_return_t  memcached_set(memcached_st *ptr,  const  char *key,
       size_t key_length, const	char *value, size_t value_length, time_t expi-
       ration, 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 expi-
       ration, 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 expi-
       ration, 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 expi-
       ration, 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 expi-
       ration, uint32_t	flags)

       Compile and link	with -lmemcached

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  charac-
       ters 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 li-
       braries 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 al-
       ready 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  oc-
       curs.

       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_cas()	overwrites  data  in  the  server as long as the "cas"
       value is	still the same in the server. You can get the cas value	 of  a
       result  by  calling  memcached_result_cas() on a	memcached_result_st(3)
       structure. At the point that this note was written cas is  still	 buggy
       in  memached.  Turning  on tests	for it in libmemcached(3) is optional.
       Please see memcached_set	for information	on how to do this.

       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  testsed  with	 the  MEMCACHED_BEHAV-
       IOR_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 be-
       ing executed. When running with the binary  protocol,  MEMCACHED_BEHAV-
       IOR_BINARY_PROTOCOL,  the  size of the key,value, flags and expiry com-
       bined may not exceed 1368 bytes.	When running with the ASCII  protocol,
       the  exact  limit  fluctuates depending on which	function is being exe-
       cuted 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,  ex-
       ceeds 1400 bytes, a MEMCACHED_WRITE_FAILURE will	be returned.

RETURN
       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
       legitmate error in the case of a	collision.

HOME
       To find out more	information please check: http://libmemcached.org/

SEE ALSO
       memcached(1) libmemached(3) memcached_strerror(3)  memcached_prepend(3)
       memcached_cas(3)	memcached_append(3)

AUTHOR
       Brian Aker

COPYRIGHT
       2011-2013, Brian	Aker DataDifferential, http://datadifferential.com/

1.0.18			       February	09, 2014       MEMCACHED_ADD_BY_KEY(3)

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