1MEMCACHED_MGET_BY_KEY(3) libmemcached MEMCACHED_MGET_BY_KEY(3)
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6 memcached_mget_by_key - Retrieving data from the server
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9 #include <libmemcached/memcached.h>
10 memcached_result_st * memcached_fetch_result(memcached_st *ptr, mem‐
12 cached_result_st *result, memcached_return_t *error)
13 char * memcached_get(memcached_st *ptr, const char *key,
15 size_t key_length, size_t *value_length, uint32_t *flags, mem‐
16 cached_return_t *error)
17 memcached_return_t memcached_mget(memcached_st *ptr, const char *
19 const *keys, const size_t *key_length, size_t number_of_keys)
20 char * memcached_get_by_key(memcached_st *ptr, const char *group_key,
22 size_t group_key_length, const char *key, size_t key_length,
23 size_t *value_length, uint32_t *flags, memcached_return_t *error)
24 memcached_return_t memcached_mget_by_key(memcached_st *ptr, const
26 char *group_key, size_t group_key_length, const char * const *keys,
27 const size_t *key_length, size_t number_of_keys)
28 memcached_return_t memcached_fetch_execute(memcached_st *ptr,
30 memcached_execute_fn *callback, void *context, uint32_t number_of_call‐
31 backs)
32 memcached_return_t memcached_mget_execute(memcached_st *ptr, const char
34 * const *keys, const size_t *key_length, size_t number_of_keys,
35 memcached_execute_fn *callback, void *context, uint32_t number_of_call‐
36 backs)
37 memcached_return_t memcached_mget_execute_by_key(memcached_st *ptr,
39 const char *group_key, size_t group_key_length, const char *
40 const *keys, const size_t *key_length, size_t number_of_keys,
41 memcached_execute_fn *callback, void *context, uint32_t number_of_call‐
42 backs)
43 memcached_return_t (*memcached_execute_fn)(const memcached_st *ptr,
45 memcached_result_st *result, void *context)
46 Compile and link with -lmemcached
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50 memcached_get() is used to fetch an individual value from the server.
51 You must pass in a key and its length to fetch the object. You must
52 supply three pointer variables which will give you the state of the
53 returned object. A uint32_t pointer to contain whatever flags you
54 stored with the value, a size_t pointer which will be filled with size
55 of of the object, and a memcached_return_t pointer to hold any error.
56 The object will be returned upon success and NULL will be returned on
57 failure. Any object returned by memcached_get() must be released by the
58 caller application.
59 memcached_mget() is used to select multiple keys at once. For multiple
61 key operations it is always faster to use this function. This function
62 always works asynchronously.
63 To retrieve data after a successful execution of memcached_mget(), you
65 will need to call memcached_fetch_result(). You should continue to
66 call this function until it returns a NULL (i.e. no more values). If
67 you need to quit in the middle of a memcached_mget() call, you can exe‐
68 cute a memcached_quit(), those this is not required.
69 memcached_fetch_result() is used to fetch an individual value from the
71 server. memcached_mget() must always be called before using this
72 method. You must pass in a key and its length to fetch the object. You
73 must supply three pointer variables which will give you the state of
74 the returned object. A uint32_t pointer to contain whatever flags you
75 stored with the value, a size_t pointer which will be filled with size
76 of of the object, and a memcached_return_t pointer to hold any error.
77 The object will be returned upon success and NULL will be returned on
78 failure. MEMCACHED_END is returned by the *error value when all objects
79 that have been found are returned. The final value upon MEMCACHED_END
80 is null.
81 memcached_fetch_result() is used to return a memcached_result_st struc‐
83 ture from a memcached server. The result object is forward compatible
84 with changes to the server. For more information please refer to the
85 memcached_result_st help. This function will dynamically allocate a
86 result structure for you if you do not pass one to the function.
87 memcached_fetch_execute() is a callback function for result sets.
89 Instead of returning the results to you for processing, it passes each
90 of the result sets to the list of functions you provide. It passes to
91 the function a memcached_st that can be cloned for use in the called
92 function (it can not be used directly). It also passes a result set
93 which does not need to be freed. Finally it passes a "context". This is
94 just a pointer to a memory reference you supply the calling function.
95 Currently only one value is being passed to each function call. In the
96 future there will be an option to allow this to be an array.
97 memcached_mget_execute() and memcached_mget_execute_by_key() is similar
99 to memcached_mget(), but it may trigger the supplied callbacks with
100 result sets while sending out the queries. If you try to perform a
101 really large multiget with memcached_mget() you may encounter a dead‐
102 lock in the OS kernel (it will fail to write data to the socket because
103 the input buffer is full). memcached_mget_execute() solves this problem
104 by processing some of the results before continuing sending out
105 requests. Please note that this function is only available in the
106 binary protocol.
107 memcached_get_by_key() and memcached_mget_by_key() behave in a similar
109 nature as memcached_get() and memcached_mget(). The difference is that
110 they take a master key that is used for determining which server an
111 object was stored if key partitioning was used for storage.
112 All of the above functions are not tested when the MEMCACHED_BEHAV‐
114 IOR_USE_UDP has been set. Executing any of these functions with this
115 behavior on will result in MEMCACHED_NOT_SUPPORTED being returned, or
116 for those functions which do not return a memcached_return_t, the error
117 function parameter will be set to MEMCACHED_NOT_SUPPORTED.
118
120 All objects retrieved via memcached_get() or memcached_get_by_key()
121 must be freed with free(3).
122 memcached_get() will return NULL on error. You must look at the value
124 of error to determine what the actual error was.
125 memcached_fetch_execute() return MEMCACHED_SUCCESS if all keys were
127 successful. MEMCACHED_NOTFOUND will be return if no keys at all were
128 found.
129 memcached_fetch_result() sets error to MEMCACHED_END upon successful
131 conclusion. MEMCACHED_NOTFOUND will be return if no keys at all were
132 found.
133
135 To find out more information please check: http://libmemcached.org/
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138 memcached(1) libmemcached(3) memcached_strerror(3)
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141 Brian Aker
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144 2011-2013, Brian Aker DataDifferential, http://datadifferential.com/
1451.0.18 February 09, 2014 MEMCACHED_MGET_BY_KEY(3)