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

   1 .TH "MEMCACHED_MGET" "3" "April 04, 2012" "1.0.6" "libmemcached"
   2 .SH NAME
   3 memcached_mget \- 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\fI\ *ptr\fP, memcached_result_st\fI\ *result\fP, memcached_return_t\fI\ *error\fP)
  39 .UNINDENT
  40 .INDENT 0.0
  41 .TP
  42 .B char * memcached_get(memcached_st\fI\ *ptr\fP, const char\fI\ *key\fP, size_t\fI\ key_length\fP, size_t\fI\ *value_length\fP, uint32_t\fI\ *flags\fP, memcached_return_t\fI\ *error\fP)
  43 .UNINDENT
  44 .INDENT 0.0
  45 .TP
  46 .B memcached_return_t memcached_mget(memcached_st\fI\ *ptr\fP, const char * const\fI\ *keys\fP, const size_t\fI\ *key_length\fP, size_t\fI\ number_of_keys\fP)
  47 .UNINDENT
  48 .INDENT 0.0
  49 .TP
  50 .B char * memcached_get_by_key(memcached_st\fI\ *ptr\fP, const char\fI\ *group_key\fP, size_t\fI\ group_key_length\fP, const char\fI\ *key\fP, size_t\fI\ key_length\fP, size_t\fI\ *value_length\fP, uint32_t\fI\ *flags\fP, memcached_return_t\fI\ *error\fP)
  51 .UNINDENT
  52 .INDENT 0.0
  53 .TP
  54 .B memcached_return_t memcached_mget_by_key(memcached_st\fI\ *ptr\fP, const char\fI\ *group_key\fP, size_t\fI\ group_key_length\fP, const char * const\fI\ *keys\fP, const size_t\fI\ *key_length\fP, size_t\fI\ number_of_keys\fP)
  55 .UNINDENT
  56 .INDENT 0.0
  57 .TP
  58 .B memcached_return_t memcached_fetch_execute(memcached_st\fI\ *ptr\fP, \fI\%memcached_execute_fn\fP\fI\ *callback\fP, void\fI\ *context\fP, uint32_t\fI\ number_of_callbacks\fP)
  59 .UNINDENT
  60 .INDENT 0.0
  61 .TP
  62 .B memcached_return_t memcached_mget_execute(memcached_st\fI\ *ptr\fP, const char * const\fI\ *keys\fP, const size_t\fI\ *key_length\fP, size_t\fI\ number_of_keys\fP, \fI\%memcached_execute_fn\fP\fI\ *callback\fP, void\fI\ *context\fP, uint32_t\fI\ number_of_callbacks\fP)
  63 .UNINDENT
  64 .INDENT 0.0
  65 .TP
  66 .B memcached_return_t memcached_mget_execute_by_key(memcached_st\fI\ *ptr\fP, const char\fI\ *group_key\fP, size_t\fI\ group_key_length\fP, const char * const\fI\ *keys\fP, const size_t\fI\ *key_length\fP, size_t\fI\ number_of_keys\fP, \fI\%memcached_execute_fn\fP\fI\ *callback\fP, void\fI\ *context\fP, uint32_t\fI\ number_of_callbacks\fP)
  67 .UNINDENT
  68 .INDENT 0.0
  69 .TP
  70 .B memcached_return_t (*memcached_execute_fn)(const memcached_st\fI\ *ptr\fP, memcached_result_st\fI\ *result\fP, void\fI\ *context\fP)
  71 .UNINDENT
  72 .sp
  73 Compile and link with \-lmemcached
  74 .SH DESCRIPTION
  75 .sp
  76 \fI\%memcached_get()\fP is used to fetch an individual value from the server.
  77 You 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 \fBuint32_t\fP pointer to contain whatever flags you stored with the value, a \fBsize_t\fP pointer which will be filled with size of of
  80 the object, and a \fBmemcached_return_t\fP pointer to hold any error. The
  81 object will be returned upon success and NULL will be returned on failure. Any
  82 object returned by \fI\%memcached_get()\fP must be released by the caller
  83 application.
  84 .sp
  85 \fI\%memcached_mget()\fP is used to select multiple keys at once. For
  86 multiple key operations it is always faster to use this function. This function always works asynchronously.
  87 .sp
  88 To retrieve data after a successful execution of \fI\%memcached_mget()\fP, you will need to
  89 call \fI\%memcached_fetch_result()\fP.  You should continue to call this function until
  90 it returns a NULL (i.e. no more values). If you need to quit in the middle of a
  91 \fI\%memcached_mget()\fP call, you can execute a \fBmemcached_quit()\fP, those this is not required.
  92 .sp
  93 \fI\%memcached_fetch_result()\fP is used to fetch an individual value from the server. \fI\%memcached_mget()\fP must always be called before using this method.
  94 You must pass in a key and its length to fetch the object. You must supply
  95 three pointer variables which will give you the state of the returned
  96 object.  A \fBuint32_t\fP pointer to contain whatever flags you stored with the value, a \fBsize_t\fP pointer which will be filled with size of of the
  97 object, and a \fBmemcached_return_t\fP pointer to hold any error. The
  98 object will be returned upon success and NULL will be returned on failure. \fBMEMCACHED_END\fP is returned by the *error value when all objects that have been found are returned. The final value upon \fBMEMCACHED_END\fP is null.
  99 .sp
 100 \fI\%memcached_fetch_result()\fP is used to return a \fBmemcached_result_st\fP structure from a memcached server. The result object is forward compatible
 101 with changes to the server. For more information please refer to the
 102 \fBmemcached_result_st\fP help. This function will dynamically allocate a
 103 result structure for you if you do not pass one to the function.
 104 .sp
 105 \fI\%memcached_fetch_execute()\fP is a callback function for result sets.
 106 Instead of returning the results to you for processing, it passes each of the
 107 result sets to the list of functions you provide. It passes to the function
 108 a \fBmemcached_st\fP that can be cloned for use in the called
 109 function (it can not be used directly). It also passes a result set which does
 110 not need to be freed. Finally it passes a "context". This is just a pointer to
 111 a memory reference you supply the calling function. Currently only one value
 112 is being passed to each function call. In the future there will be an option
 113 to allow this to be an array.
 114 .sp
 115 \fI\%memcached_mget_execute()\fP and \fI\%memcached_mget_execute_by_key()\fP
 116 is similar to \fI\%memcached_mget()\fP, but it may trigger the supplied
 117 callbacks with result sets while sending out the queries. If you try to
 118 perform a really large multiget with \fI\%memcached_mget()\fP you may
 119 encounter a deadlock in the OS kernel (it will fail to write data to the
 120 socket because the input buffer is full). \fI\%memcached_mget_execute()\fP
 121 solves this problem by processing some of the results before continuing
 122 sending out requests. Please note that this function is only available in
 123 the binary protocol.
 124 .sp
 125 \fI\%memcached_get_by_key()\fP and \fI\%memcached_mget_by_key()\fP behave
 126 in a similar nature as \fI\%memcached_get()\fP and \fI\%memcached_mget()\fP.
 127 The difference is that they take a master key that is used for determining
 128 which server an object was stored if key partitioning was used for storage.
 129 .sp
 130 All of the above functions are not tested when the
 131 \fBMEMCACHED_BEHAVIOR_USE_UDP\fP has been set. Executing any of these
 132 functions with this behavior on will result in \fBMEMCACHED_NOT_SUPPORTED\fP being returned, or for those functions which do not return a \fBmemcached_return_t\fP, the error function parameter will be set to \fBMEMCACHED_NOT_SUPPORTED\fP.
 133 .SH RETURN
 134 .sp
 135 All objects retrieved via \fI\%memcached_get()\fP or \fI\%memcached_get_by_key()\fP must be freed with \fIfree(3)\fP.
 136 .sp
 137 \fI\%memcached_get()\fP will return NULL on
 138 error. You must look at the value of error to determine what the actual error
 139 was.
 140 .sp
 141 \fI\%memcached_fetch_execute()\fP return \fBMEMCACHED_SUCCESS\fP if
 142 all keys were successful. \fBMEMCACHED_NOTFOUND\fP will be return if no
 143 keys at all were found.
 144 .sp
 145 \fI\%memcached_fetch_result()\fP sets error
 146 to \fBMEMCACHED_END\fP upon successful conclusion.
 147 \fBMEMCACHED_NOTFOUND\fP will be return if no keys at all were found.
 148 .SH HOME
 149 .sp
 150 To find out more information please check:
 151 \fI\%http://libmemcached.org/\fP
 152 .SH SEE ALSO
 153 .sp
 154 \fImemcached(1)\fP \fIlibmemcached(3)\fP \fImemcached_strerror(3)\fP
 155 .SH AUTHOR
 156 Brian Aker
 157 .SH COPYRIGHT
 158 2011, Brian Aker DataDifferential, http://datadifferential.com/
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