NAME

       memcached_mget_by_key - Retrieving data from the server

SYNOPSIS

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

       memcached_result_st    *memcached_fetch_result(memcached_st    *ptr,   memcached_result_st
       *result, memcached_return_t *error)

       char  *memcached_get(memcached_st  *ptr,  const  char  *key,  size_t  key_length,   size_t
       *value_length, uint32_t *flags, memcached_return_t *error)

       memcached_return_t memcached_mget(memcached_st *ptr, const char *const *keys, const size_t
       *key_length, size_t number_of_keys)

       char   *memcached_get_by_key(memcached_st   *ptr,   const    char    *group_key,    size_t
       group_key_length,  const  char  *key,  size_t  key_length,  size_t *value_length, uint32_t
       *flags, memcached_return_t *error)

       memcached_return_t memcached_mget_by_key(memcached_st *ptr, const char *group_key,  size_t
       group_key_length,   const   char   *const   *keys,   const   size_t   *key_length,  size_t
       number_of_keys)

       memcached_return_t   memcached_fetch_execute(memcached_st    *ptr,    memcached_execute_fn
       *callback, void *context, uint32_t number_of_callbacks)

       memcached_return_t  memcached_mget_execute(memcached_st  *ptr,  const  char  *const *keys,
       const size_t *key_length,  size_t  number_of_keys,  memcached_execute_fn  *callback,  void
       *context, uint32_t number_of_callbacks)

       memcached_return_t memcached_mget_execute_by_key(memcached_st *ptr, const char *group_key,
       size_t group_key_length,  const  char  *const  *keys,  const  size_t  *key_length,  size_t
       number_of_keys,     memcached_execute_fn     *callback,     void     *context,    uint32_t
       number_of_callbacks)

       typedef    memcached_return_t     (*memcached_execute_fn)(const     memcached_st     *ptr,
       memcached_result_st *result, void *context)

DESCRIPTION

       memcached_get()  is used to fetch an individual value from the server.  You must pass in a
       key and its length to fetch the object. You must supply three pointer variables which will
       give  you  the state of the returned object.  A uint32_t pointer to contain whatever flags
       you stored with the value, a size_t pointer which will be  filled  with  size  of  of  the
       object,  and  a  memcached_return_t pointer to hold any error. The object will be returned
       upon success and NULL will be returned on failure. Any object returned by  memcached_get()
       must be released by the caller application.

       memcached_mget()  is  used to select multiple keys at once. For multiple key operations it
       is always faster to use this function.  This function always works asynchronously.

       To retrieve data after a successful execution of memcached_mget(), you will need  to  call
       memcached_fetch_result().   You  should  continue to call this function until it returns a
       NULL (i.e. no more values). If you need to quit in the middle of a memcached_mget()  call,
       you can execute a memcached_quit(), those this is not required.

       memcached_fetch_result()   is   used  to  fetch  an  individual  value  from  the  server.
       memcached_mget() must always be called before using this method.  You must pass in  a  key
       and  its  length  to  fetch the object. You must supply three pointer variables which will
       give you the state of the returned object.  A uint32_t pointer to contain  whatever  flags
       you  stored  with  the  value,  a  size_t pointer which will be filled with size of of the
       object, and a memcached_return_t pointer to hold any error. The object  will  be  returned
       upon success and NULL will be returned on failure. MEMCACHED_END is returned by the *error
       value when all objects that have been found have  been  returned.  The  final  value  upon
       MEMCACHED_END is null.

       memcached_fetch_result()  is  used  to  return  a  memcached_result_st  structure  from  a
       memcached server. The result object is forward compatible with changes to the server.  For
       more  information  please  refer  to  the  memcached_result_st  help.  This  function will
       dynamically allocate a result structure for you if you do not pass one to the function.

       memcached_fetch_execute() is a callback function for result sets.   Instead  of  returning
       the  results  to  you  for  processing,  it  passes each of the result sets to the list of
       functions you provide. It passes to the function a memcached_st that can be cloned for use
       in  the  called  function (it can not be used directly). It also passes a result set which
       does not need to be freed. Finally it passes a "context". This is  just  a  pointer  to  a
       memory reference you supply the calling function. Currently only one value is being passed
       to each function call. In the future there will be an option to allow this to be an array.

       memcached_mget_execute()    and    memcached_mget_execute_by_key()    is    similar     to
       memcached_mget(), but it may trigger the supplied callbacks with result sets while sending
       out the queries. If you try to perform a really large multiget with  memcached_mget()  you
       may  encounter  a  deadlock  in  the  OS  kernel (it will fail to write data to the socket
       because the input  buffer  is  full).  memcached_mget_execute()  solves  this  problem  by
       processing  some  of  the results before continuing sending out requests. Please note that
       this function is only available in the binary protocol.

       memcached_get_by_key()  and  memcached_mget_by_key()  behave  in  a  similar   nature   as
       memcached_get()  and memcached_mget().  The difference is that they take a master key that
       is used for determining which server an object was stored if key partitioning was used for
       storage.

       All  of  the  above  functions are not tested when the MEMCACHED_BEHAVIOR_USE_UDP has been
       set.  Executing  any  of  these  functions  with  this  behavior   on   will   result   in
       MEMCACHED_NOT_SUPPORTED  being  returned,  or  for  those  functions which do not return a
       memcached_return_t, the error function parameter will be set to MEMCACHED_NOT_SUPPORTED.

RETURN VALUE

       All objects retrieved via memcached_get() or memcached_get_by_key()  must  be  freed  with
       free(3).

       memcached_get()  will  return  NULL  on  error.   You  must  look at the value of error to
       determine what the actual error was.

       memcached_fetch_execute()  return  MEMCACHED_SUCCESS  if   all   keys   were   successful.
       MEMCACHED_NOTFOUND will be returned if no keys at all were found.

       memcached_fetch_result()   sets   error   to  MEMCACHED_END  upon  successful  conclusion.
       MEMCACHED_NOTFOUND will be returned if no keys at all were found.

SEE ALSO

       memcached(1) libmemcached(3) memcached_strerror(3)