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MEMCACHED_MGET(3) libmemcached MEMCACHED_MGET(3)
NAME
memcached_mget - Retrieving data from the server
SYNOPSIS
#include <libmemcached/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 *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)
memcached_return_t (*memcached_execute_fn)(const memcached_st *ptr,
memcached_result_st *result, void *context)
Compile and link with -lmemcached
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 are 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
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 return if no keys at all were
found.
memcached_fetch_result() sets error to MEMCACHED_END upon successful
conclusion. MEMCACHED_NOTFOUND will be return if no keys at all were
found.
HOME
To find out more information please check: http://libmemcached.org/
SEE ALSO
memcached(1) libmemcached(3) memcached_strerror(3)
AUTHOR
Brian Aker
COPYRIGHT
2011-2013, Brian Aker DataDifferential, http://datadifferential.com/
1.0.18 February 9, 2014 MEMCACHED_MGET(3)