Ubuntu Manpage: memcached_mget - Retrieving data from the server

Provided by: libmemcached-dev_1.1.4-1.1build3_amd64

NAME

       memcached_mget - 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.

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

SEE ALSO