NAME

       memcached_mget_execute - 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)