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NAME

       memcached_get, memcached_mget, memcached_fetch, memcached_mget_execute,
       memcached_mget_execute_by_key - Get a value

LIBRARY

       C Client Library for memcached (libmemcached, -lmemcached)

SYNOPSIS

         #include <memcached.h>

         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 *master_key, size_t master_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 *master_key, size_t master_key_length,
                                  const char * const *keys,
                                  const size_t *key_length,
                                  size_t number_of_keys);

         char *
           memcached_fetch (memcached_st *ptr,
                            char *key, size_t *key_length,
                            size_t *value_length,
                            uint32_t *flags,
                            memcached_return_t *error);

         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 *master_key,
                                          size_t master_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);

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. memcached_fetch() is then used to retrieve
       any keys found. No error is given on keys that are not found. You must
       call either memcached_fetch() or memcached_fetch_result() after a
       successful call to memcached_mget(). You should continue to call these
       functions until they return NULL (aka no more values). If you need to
       quit in the middle of a memcached_get() call, execute a
       memcached_quit(). After you do this, you can issue new queries against
       the server.

       memcached_fetch() 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.
       MEMCACHD_END is returned by the *error value when all objects that have
       been found are returned.  The final value upon MEMCACHED_END is null.
       Values returned by memcached_fetch() musted be freeā€™ed by the caller.
       memcached_fetch() will be DEPRECATED in the near future,
       memcached_fetch_result() should be used instead.

       memcached_fetch_result() is used to return a memcached_result_st(3)
       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(3) 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 (we 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 supported 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

       All objects returned must be freed by the calling application.
       memcached_get() and memcached_fetch() will return NULL on error. You
       must look at the value of error to determine what the actual error was.

       MEMCACHED_KEY_TOO_BIG is set to error whenever memcached_fetch() was
       used and the key was set larger then MEMCACHED_MAX_KEY, which was the
       largest key allowed for the original memcached ascii server.

HOME

       To find out more information please check:
       <https://launchpad.net/libmemcached>

AUTHOR

       Brian Aker, <brian@tangent.org>

SEE ALSO

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

                                  2010-01-19     memcached_mget_execute.pop(3)