1memcached_get.pop(3) memcached_get memcached_get.pop(3)
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6 memcached_get, memcached_mget, memcached_fetch, memcached_mget_execute,
7 memcached_mget_execute_by_key - Get a value
8
10 C Client Library for memcached (libmemcached, -lmemcached)
11
13 #include <memcached.h>
14 memcached_result_st *
16 memcached_fetch_result (memcached_st *ptr,
17 memcached_result_st *result,
18 memcached_return_t *error);
19 char *
21 memcached_get (memcached_st *ptr,
22 const char *key, size_t key_length,
23 size_t *value_length,
24 uint32_t *flags,
25 memcached_return_t *error);
26 memcached_return_t
28 memcached_mget (memcached_st *ptr,
29 const char * const *keys,
30 const size_t *key_length,
31 size_t number_of_keys);
32 char *
33 memcached_get_by_key (memcached_st *ptr,
34 const char *master_key, size_t master_key_length,
35 const char *key, size_t key_length,
36 size_t *value_length,
37 uint32_t *flags,
38 memcached_return_t *error);
39 memcached_return_t
41 memcached_mget_by_key (memcached_st *ptr,
42 const char *master_key, size_t master_key_length,
43 const char * const *keys,
44 const size_t *key_length,
45 size_t number_of_keys);
46 char *
48 memcached_fetch (memcached_st *ptr,
49 char *key, size_t *key_length,
50 size_t *value_length,
51 uint32_t *flags,
52 memcached_return_t *error);
53 memcached_return_t
55 memcached_fetch_execute (memcached_st *ptr,
56 memcached_execute_fn *callback,
57 void *context,
58 uint32_t number_of_callbacks);
59 memcached_return_t
62 memcached_mget_execute (memcached_st *ptr,
63 const char * const *keys,
64 const size_t *key_length,
65 size_t number_of_keys,
66 memcached_execute_fn *callback,
67 void *context,
68 uint32_t number_of_callbacks);
69 memcached_return_t
71 memcached_mget_execute_by_key (memcached_st *ptr,
72 const char *master_key,
73 size_t master_key_length,
74 const char * const *keys,
75 const size_t *key_length,
76 size_t number_of_keys,
77 memcached_execute_fn *callback,
78 void *context,
79 uint32_t number_of_callbacks);
80
82 memcached_get() is used to fetch an individual value from the server.
83 You must pass in a key and its length to fetch the object. You must
84 supply three pointer variables which will give you the state of the
85 returned object. A uint32_t pointer to contain whatever flags you
86 stored with the value, a size_t pointer which will be filled with size
87 of of the object, and a memcached_return_t pointer to hold any error.
88 The object will be returned upon success and NULL will be returned on
89 failure. Any object returned by memcached_get() must be released by the
90 caller application.
91 memcached_mget() is used to select multiple keys at once. For multiple
93 key operations it is always faster to use this function. This function
94 always works asynchronously. memcached_fetch() is then used to retrieve
95 any keys found. No error is given on keys that are not found. You must
96 call either memcached_fetch() or memcached_fetch_result() after a
97 successful call to memcached_mget(). You should continue to call these
98 functions until they return NULL (aka no more values). If you need to
99 quit in the middle of a memcached_get() call, execute a
100 memcached_quit(). After you do this, you can issue new queries against
101 the server.
102 memcached_fetch() is used to fetch an individual value from the server.
104 memcached_mget() must always be called before using this method. You
105 must pass in a key and its length to fetch the object. You must supply
106 three pointer variables which will give you the state of the returned
107 object. A uint32_t pointer to contain whatever flags you stored with
108 the value, a size_t pointer which will be filled with size of of the
109 object, and a memcached_return_t pointer to hold any error. The object
110 will be returned upon success and NULL will be returned on failure.
111 MEMCACHD_END is returned by the *error value when all objects that have
112 been found are returned. The final value upon MEMCACHED_END is null.
113 Values returned by memcached_fetch() musted be free'ed by the caller.
114 memcached_fetch() will be DEPRECATED in the near future,
115 memcached_fetch_result() should be used instead.
116 memcached_fetch_result() is used to return a memcached_result_st(3)
118 structure from a memcached server. The result object is forward
119 compatible with changes to the server. For more information please
120 refer to the memcached_result_st(3) help. This function will
121 dynamically allocate a result structure for you if you do not pass one
122 to the function.
123 memcached_fetch_execute() is a callback function for result sets.
125 Instead of returning the results to you for processing, it passes each
126 of the result sets to the list of functions you provide. It passes to
127 the function a memcached_st that can be cloned for use in the called
128 function (it can not be used directly). It also passes a result set
129 which does not need to be freed. Finally it passes a "context". This
130 is just a pointer to a memory reference you supply the calling
131 function. Currently only one value is being passed to each function
132 call. In the future there will be an option to allow this to be an
133 array.
134 memcached_mget_execute() and memcached_mget_execute_by_key() is similar
136 to memcached_mget(), but it may trigger the supplied callbacks with
137 result sets while sending out the queries. If you try to perform a
138 really large multiget with memcached_mget() you may encounter a
139 deadlock in the OS kernel (we fail to write data to the socket because
140 the input buffer is full). memcached_mget_execute() solves this problem
141 by processing some of the results before continuing sending out
142 requests. Please note that this function is only available in the
143 binary protocol.
144 memcached_get_by_key() and memcached_mget_by_key() behave in a similar
146 nature as memcached_get() and memcached_mget(). The difference is that
147 they take a master key that is used for determining which server an
148 object was stored if key partitioning was used for storage.
149 All of the above functions are not supported when the
151 "MEMCACHED_BEHAVIOR_USE_UDP" has been set. Executing any of these
152 functions with this behavior on will result in
153 "MEMCACHED_NOT_SUPPORTED" being returned or, for those functions which
154 do not return a "memcached_return_t", the error function parameter will
155 be set to "MEMCACHED_NOT_SUPPORTED".
156
158 All objects returned must be freed by the calling application.
159 memcached_get() and memcached_fetch() will return NULL on error. You
160 must look at the value of error to determine what the actual error was.
161 MEMCACHED_KEY_TOO_BIG is set to error whenever memcached_fetch() was
163 used and the key was set larger then MEMCACHED_MAX_KEY, which was the
164 largest key allowed for the original memcached ascii server.
165
167 To find out more information please check:
168 <https://launchpad.net/libmemcached>
169
171 Brian Aker, <brian@tangent.org>
172
174 memcached(1) libmemcached(3) memcached_strerror(3)
175 2010-06-28 memcached_get.pop(3)