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

   1 .TH "MEMCACHED_FETCH" "3" "June 17, 2011" "0.49" "libmemcached"
   2 .SH NAME
   3 memcached_fetch \- Retrieving data from the server
   4 .
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  32 .
  33 .SH SYNOPSIS
  34 .sp
  35 #include <libmemcached/memcached.h>
  36 .INDENT 0.0
  37 .TP
  38 .B memcached_result_st * memcached_fetch_result (memcached_st *ptr, memcached_result_st *result, memcached_return_t *error);
  39 .UNINDENT
  40 .INDENT 0.0
  41 .TP
  42 .B char * memcached_get (memcached_st *ptr, const char *key, size_t key_length, size_t *value_length, uint32_t *flags, memcached_return_t *error);
  43 .UNINDENT
  44 .INDENT 0.0
  45 .TP
  46 .B memcached_return_t memcached_mget (memcached_st *ptr, const char * const *keys, const size_t *key_length, size_t number_of_keys);
  47 .UNINDENT
  48 .INDENT 0.0
  49 .TP
  50 .B 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);
  51 .UNINDENT
  52 .INDENT 0.0
  53 .TP
  54 .B 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);
  55 .UNINDENT
  56 .INDENT 0.0
  57 .TP
  58 .B char * memcached_fetch (memcached_st *ptr, char *key, size_t *key_length, size_t *value_length, uint32_t *flags, memcached_return_t *error);
  59 .UNINDENT
  60 .INDENT 0.0
  61 .TP
  62 .B memcached_return_t memcached_fetch_execute (memcached_st *ptr, memcached_execute_fn *callback, void *context, uint32_t number_of_callbacks);
  63 .UNINDENT
  64 .INDENT 0.0
  65 .TP
  66 .B 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);
  67 .UNINDENT
  68 .INDENT 0.0
  69 .TP
  70 .B 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);
  71 .UNINDENT
  72 .sp
  73 Compile and link with \-lmemcached
  74 .SH DESCRIPTION
  75 .sp
  76 memcached_get() is used to fetch an individual value from the server. You
  77 must pass in a key and its length to fetch the object. You must supply
  78 three pointer variables which will give you the state of the returned
  79 object.  A uint32_t pointer to contain whatever flags you stored with the value,
  80 a size_t pointer which will be filled with size of of the object, and a
  81 memcached_return_t pointer to hold any error. The object will be returned
  82 upon success and NULL will be returned on failure. Any object returned by
  83 memcached_get() must be released by the caller application.
  84 .sp
  85 memcached_mget() is used to select multiple keys at once. For multiple key
  86 operations it is always faster to use this function. This function always
  87 works asynchronously. memcached_fetch() is then used to retrieve any keys
  88 found. No error is given on keys that are not found. You must call either
  89 memcached_fetch() or memcached_fetch_result() after a successful call to
  90 memcached_mget(). You should continue to call these functions until they
  91 return NULL (aka no more values). If you need to quit in the middle of a
  92 memcached_get() call, execute a memcached_quit(). After you do this, you can
  93 issue new queries against the server.
  94 .sp
  95 memcached_fetch() is used to fetch an individual value from the server.
  96 memcached_mget() must always be called before using this method.  You
  97 must pass in a key and its length to fetch the object. You must supply
  98 three pointer variables which will give you the state of the returned
  99 object.  A uint32_t pointer to contain whatever flags you stored with the value,
 100 a size_t pointer which will be filled with size of of the object, and a
 101 memcached_return_t pointer to hold any error. The object will be returned
 102 upon success and NULL will be returned on failure. \fBMEMCACHD_END\fP is
 103 returned by the *error value when all objects that have been found are
 104 returned.  The final value upon \fBMEMCACHED_END\fP is null. Values
 105 returned by memcached_fetch() must be freed by the caller. memcached_fetch()
 106 will be DEPRECATED in the near future, memcached_fetch_result() should be
 107 used instead.
 108 .sp
 109 memcached_fetch_result() is used to return a memcached_result_st(3) structure
 110 from a memcached server. The result object is forward compatible with changes
 111 to the server. For more information please refer to the memcached_result_st(3)
 112 help. This function will dynamically allocate a result structure for you
 113 if you do not pass one to the function.
 114 .sp
 115 memcached_fetch_execute() is a callback function for result sets. Instead
 116 of returning the results to you for processing, it passes each of the
 117 result sets to the list of functions you provide. It passes to the function
 118 a memcached_st that can be cloned for use in the called function (it can not
 119 be used directly). It also passes a result set which does not need to be freed.
 120 Finally it passes a "context". This is just a pointer to a memory reference
 121 you supply the calling function. Currently only one value is being passed
 122 to each function call. In the future there will be an option to allow this
 123 to be an array.
 124 .sp
 125 memcached_mget_execute() and memcached_mget_execute_by_key() is
 126 similar to memcached_mget(), but it may trigger the supplied callbacks
 127 with result sets while sending out the queries. If you try to perform
 128 a really large multiget with memcached_mget() you may encounter a
 129 deadlock in the OS kernel (it will fail to write data to the socket because
 130 the input buffer is full). memcached_mget_execute() solves this
 131 problem by processing some of the results before continuing sending
 132 out requests. Please note that this function is only available in the
 133 binary protocol.
 134 .sp
 135 memcached_get_by_key() and memcached_mget_by_key() behave in a similar nature
 136 as memcached_get() and memcached_mget(). The difference is that they take
 137 a master key that is used for determining which server an object was stored
 138 if key partitioning was used for storage.
 139 .sp
 140 All of the above functions are not tested when the \fBMEMCACHED_BEHAVIOR_USE_UDP\fPhas been set. Executing any of these functions with this behavior on will result in
 141 \fBMEMCACHED_NOT_SUPPORTED\fP being returned, or for those functions which do not return
 142 a \fBmemcached_return_t\fP, the error function parameter will be set to
 143 \fBMEMCACHED_NOT_SUPPORTED\fP.
 144 .SH RETURN
 145 .sp
 146 All objects returned must be freed by the calling application.
 147 memcached_get() and memcached_fetch() will return NULL on error. You must
 148 look at the value of error to determine what the actual error was.
 149 .sp
 150 \fBmemcached_fetch_execute()\fP return \fBMEMCACHED_SUCCESS\fP if
 151 all keys were successful. \fBMEMCACHED_NOTFOUND\fP will be return if no
 152 keys at all were found.
 153 .sp
 154 \fBmemcached_fetch()\fP and \fBmemcached_fetch_result()\fP set error
 155 to \fBMEMCACHED_END\fP upon successful conclusion.
 156 \fBMEMCACHED_NOTFOUND\fP will be return if no keys at all were found.
 157 .sp
 158 MEMCACHED_KEY_TOO_BIG is set to error whenever memcached_fetch() was used
 159 and the key was set larger then MEMCACHED_MAX_KEY, which was the largest
 160 key allowed for the original memcached ascii server.
 161 .SH HOME
 162 .sp
 163 To find out more information please check:
 164 \fI\%http://libmemcached.org/\fP
 165 .SH SEE ALSO
 166 .sp
 167 \fImemcached(1)\fP \fIlibmemcached(3)\fP \fImemcached_strerror(3)\fP
 168 .SH AUTHOR
 169 Brian Aker
 170 .SH COPYRIGHT
 171 2011, Brian Aker DataDifferential, http://datadifferential.com/
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