git.m6w6.name Git - awesomized/libmemcached/blob - docs/man/memcached_mget.3

   1 .TH "MEMCACHED_MGET" "3" "April 08, 2011" "0.47" "libmemcached"
   2 .SH NAME
   3 memcached_mget \- libmemcached Documentation
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  32 .
  33 .sp
  34 Get a value
  35 .SH LIBRARY
  36 .sp
  37 C Client Library for memcached (libmemcached, \-lmemcached)
  38 .SS SYNOPSIS
  39 .sp
  40 .nf
  41 .ft C
  42 #include <libmemcached/memcached.h>
  43
  44 memcached_result_st *
  45   memcached_fetch_result (memcached_st *ptr,
  46                           memcached_result_st *result,
  47                           memcached_return_t *error);
  48
  49 char *
  50   memcached_get (memcached_st *ptr,
  51                  const char *key, size_t key_length,
  52                  size_t *value_length,
  53                  uint32_t *flags,
  54                  memcached_return_t *error);
  55
  56 memcached_return_t
  57   memcached_mget (memcached_st *ptr,
  58                 const char * const *keys,
  59                 const size_t *key_length,
  60                 size_t number_of_keys);
  61 char *
  62   memcached_get_by_key (memcached_st *ptr,
  63                         const char *master_key, size_t master_key_length,
  64                         const char *key, size_t key_length,
  65                         size_t *value_length,
  66                         uint32_t *flags,
  67                         memcached_return_t *error);
  68
  69 memcached_return_t
  70   memcached_mget_by_key (memcached_st *ptr,
  71                          const char *master_key, size_t master_key_length,
  72                          const char * const *keys,
  73                          const size_t *key_length,
  74                          size_t number_of_keys);
  75
  76 char *
  77   memcached_fetch (memcached_st *ptr,
  78                    char *key, size_t *key_length,
  79                    size_t *value_length,
  80                    uint32_t *flags,
  81                    memcached_return_t *error);
  82
  83 memcached_return_t
  84   memcached_fetch_execute (memcached_st *ptr,
  85                            memcached_execute_fn *callback,
  86                            void *context,
  87                            uint32_t number_of_callbacks);
  88
  89
  90 memcached_return_t
  91   memcached_mget_execute (memcached_st *ptr,
  92                           const char * const *keys,
  93                           const size_t *key_length,
  94                           size_t number_of_keys,
  95                           memcached_execute_fn *callback,
  96                           void *context,
  97                           uint32_t number_of_callbacks);
  98
  99 memcached_return_t
 100   memcached_mget_execute_by_key (memcached_st *ptr,
 101                                  const char *master_key,
 102                                  size_t master_key_length,
 103                                  const char * const *keys,
 104                                  const size_t *key_length,
 105                                  size_t number_of_keys,
 106                                  memcached_execute_fn *callback,
 107                                  void *context,
 108                                  uint32_t number_of_callbacks);
 109 .ft P
 110 .fi
 111 .SS DESCRIPTION
 112 .sp
 113 memcached_get() is used to fetch an individual value from the server. You
 114 must pass in a key and its length to fetch the object. You must supply
 115 three pointer variables which will give you the state of the returned
 116 object.  A uint32_t pointer to contain whatever flags you stored with the value,
 117 a size_t pointer which will be filled with size of of the object, and a
 118 memcached_return_t pointer to hold any error. The object will be returned
 119 upon success and NULL will be returned on failure. Any object returned by
 120 memcached_get() must be released by the caller application.
 121 .sp
 122 memcached_mget() is used to select multiple keys at once. For multiple key
 123 operations it is always faster to use this function. This function always
 124 works asynchronously. memcached_fetch() is then used to retrieve any keys
 125 found. No error is given on keys that are not found. You must call either
 126 memcached_fetch() or memcached_fetch_result() after a successful call to
 127 memcached_mget(). You should continue to call these functions until they
 128 return NULL (aka no more values). If you need to quit in the middle of a
 129 memcached_get() call, execute a memcached_quit(). After you do this, you can
 130 issue new queries against the server.
 131 .sp
 132 memcached_fetch() is used to fetch an individual value from the server.
 133 memcached_mget() must always be called before using this method.  You
 134 must pass in a key and its length to fetch the object. You must supply
 135 three pointer variables which will give you the state of the returned
 136 object.  A uint32_t pointer to contain whatever flags you stored with the value,
 137 a size_t pointer which will be filled with size of of the object, and a
 138 memcached_return_t pointer to hold any error. The object will be returned
 139 upon success and NULL will be returned on failure. MEMCACHD_END is returned
 140 by the *error value when all objects that have been found are returned.
 141 The final value upon MEMCACHED_END is null. Values returned by
 142 memcached_fetch() musted be free\(aqed by the caller. memcached_fetch() will
 143 be DEPRECATED in the near future, memcached_fetch_result() should be used
 144 instead.
 145 .sp
 146 memcached_fetch_result() is used to return a memcached_result_st(3) structure
 147 from a memcached server. The result object is forward compatible with changes
 148 to the server. For more information please refer to the memcached_result_st(3)
 149 help. This function will dynamically allocate a result structure for you
 150 if you do not pass one to the function.
 151 .sp
 152 memcached_fetch_execute() is a callback function for result sets. Instead
 153 of returning the results to you for processing, it passes each of the
 154 result sets to the list of functions you provide. It passes to the function
 155 a memcached_st that can be cloned for use in the called function (it can not
 156 be used directly). It also passes a result set which does not need to be freed.
 157 Finally it passes a "context". This is just a pointer to a memory reference
 158 you supply the calling function. Currently only one value is being passed
 159 to each function call. In the future there will be an option to allow this
 160 to be an array.
 161 .sp
 162 memcached_mget_execute() and memcached_mget_execute_by_key() is
 163 similar to memcached_mget(), but it may trigger the supplied callbacks
 164 with result sets while sending out the queries. If you try to perform
 165 a really large multiget with memcached_mget() you may encounter a
 166 deadlock in the OS kernel (we fail to write data to the socket because
 167 the input buffer is full). memcached_mget_execute() solves this
 168 problem by processing some of the results before continuing sending
 169 out requests. Please note that this function is only available in the
 170 binary protocol.
 171 .sp
 172 memcached_get_by_key() and memcached_mget_by_key() behave in a similar nature
 173 as memcached_get() and memcached_mget(). The difference is that they take
 174 a master key that is used for determining which server an object was stored
 175 if key partitioning was used for storage.
 176 .sp
 177 All of the above functions are not testsed when the \fBMEMCACHED_BEHAVIOR_USE_UDP\fPhas been set. Executing any of these functions with this behavior on will result in
 178 \fBMEMCACHED_NOT_SUPPORTED\fP being returned or, for those functions which do not return
 179 a \fBmemcached_return_t\fP, the error function parameter will be set to
 180 \fBMEMCACHED_NOT_SUPPORTED\fP.
 181 .SH RETURN
 182 .sp
 183 All objects returned must be freed by the calling application.
 184 memcached_get() and memcached_fetch() will return NULL on error. You must
 185 look at the value of error to determine what the actual error was.
 186 .sp
 187 MEMCACHED_KEY_TOO_BIG is set to error whenever memcached_fetch() was used
 188 and the key was set larger then MEMCACHED_MAX_KEY, which was the largest
 189 key allowed for the original memcached ascii server.
 190 .SH HOME
 191 .sp
 192 To find out more information please check:
 193 \fI\%https://launchpad.net/libmemcached\fP
 194 .SH AUTHOR
 195 .sp
 196 Brian Aker, <\fI\%brian@tangent.org\fP>
 197 .SS SEE ALSO
 198 .sp
 199 \fImemcached(1)\fP \fIlibmemcached(3)\fP \fImemcached_strerror(3)\fP
 200 .SH AUTHOR
 201 Brian Aker
 202 .SH COPYRIGHT
 203 2011, Brian Aker DataDifferential, http://datadifferential.com/
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