MEMCACHED_FETCH_EXECUTE(3) libmemcached-awesome MEMCACHED_FETCH_EXECUTE(3)
NAME
memcached_fetch_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_call-
backs)
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_call-
backs)
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_call-
backs)
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 re-
turned 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 ob-
ject will be returned upon success and NULL will be returned on fail-
ure. 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 exe-
cute 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 struc-
ture 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 re-
sult structure for you if you do not pass one to the function.
memcached_fetch_execute() is a callback function for result sets. In-
stead 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 func-
tion (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. Cur-
rently only one value is being passed to each function call. In the fu-
ture 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 re-
sult 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 in-
put 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 proto-
col.
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 ob-
ject 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 func-
tions with this behavior on will result in MEMCACHED_NOT_SUPPORTED be-
ing 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)
1.1 Mar 06, 2023 MEMCACHED_FETCH_EXECUTE(3)
Czas wygenerowania: 0.00034 sek.
Created with the man page lookup class by Andrew Collington.
Based on a C man page viewer by Vadim Pavlov
Unicode soft-hyphen fix (as used by RedHat) by Dan Edwards
Some optimisations by Eli Argon
Caching idea and code contribution by James Richardson
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