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.TH "MEMCACHED_MGET_EXECUTE_BY_KEY" "3" "September 16, 2012" "1.0.10" "libmemcached"
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memcached_mget_execute_by_key \- Retrieving data from the server
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.\" Man page generated from reStructeredText.
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#include <libmemcached/memcached.h>
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.B memcached_result_st * memcached_fetch_result(memcached_st\fI\ *ptr\fP, memcached_result_st\fI\ *result\fP, memcached_return_t\fI\ *error\fP)
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.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)
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.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)
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.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)
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.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)
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.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)
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.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)
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.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)
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.B memcached_return_t (*memcached_execute_fn)(const memcached_st\fI\ *ptr\fP, memcached_result_st\fI\ *result\fP, void\fI\ *context\fP)
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Compile and link with \-lmemcached
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\fI\%memcached_get()\fP is used to fetch an individual value from the server.
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You must pass in a key and its length to fetch the object. You must supply
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three pointer variables which will give you the state of the returned
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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
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the object, and a \fBmemcached_return_t\fP pointer to hold any error. The
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object will be returned upon success and NULL will be returned on failure. Any
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object returned by \fI\%memcached_get()\fP must be released by the caller
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\fI\%memcached_mget()\fP is used to select multiple keys at once. For
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multiple key operations it is always faster to use this function. This function always works asynchronously.
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To retrieve data after a successful execution of \fI\%memcached_mget()\fP, you will need to
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call \fI\%memcached_fetch_result()\fP. You should continue to call this function until
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it returns a NULL (i.e. no more values). If you need to quit in the middle of a
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\fI\%memcached_mget()\fP call, you can execute a \fBmemcached_quit()\fP, those this is not required.
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\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.
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You must pass in a key and its length to fetch the object. You must supply
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three pointer variables which will give you the state of the returned
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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
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object, and a \fBmemcached_return_t\fP pointer to hold any error. The
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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.
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\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
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with changes to the server. For more information please refer to the
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\fBmemcached_result_st\fP help. This function will dynamically allocate a
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result structure for you if you do not pass one to the function.
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\fI\%memcached_fetch_execute()\fP is a callback function for result sets.
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Instead of returning the results to you for processing, it passes each of the
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result sets to the list of functions you provide. It passes to the function
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a \fBmemcached_st\fP that can be cloned for use in the called
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function (it can not be used directly). It also passes a result set which does
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not need to be freed. Finally it passes a "context". This is just a pointer to
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a memory reference you supply the calling function. Currently only one value
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is being passed to each function call. In the future there will be an option
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to allow this to be an array.
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\fI\%memcached_mget_execute()\fP and \fI\%memcached_mget_execute_by_key()\fP
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is similar to \fI\%memcached_mget()\fP, but it may trigger the supplied
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callbacks with result sets while sending out the queries. If you try to
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perform a really large multiget with \fI\%memcached_mget()\fP you may
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encounter a deadlock in the OS kernel (it will fail to write data to the
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socket because the input buffer is full). \fI\%memcached_mget_execute()\fP
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solves this problem by processing some of the results before continuing
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sending out requests. Please note that this function is only available in
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\fI\%memcached_get_by_key()\fP and \fI\%memcached_mget_by_key()\fP behave
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in a similar nature as \fI\%memcached_get()\fP and \fI\%memcached_mget()\fP.
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The difference is that they take a master key that is used for determining
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which server an object was stored if key partitioning was used for storage.
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All of the above functions are not tested when the
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\fBMEMCACHED_BEHAVIOR_USE_UDP\fP has been set. Executing any of these
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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.
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All objects retrieved via \fI\%memcached_get()\fP or \fI\%memcached_get_by_key()\fP must be freed with \fIfree(3)\fP.
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\fI\%memcached_get()\fP will return NULL on
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error. You must look at the value of error to determine what the actual error
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\fI\%memcached_fetch_execute()\fP return \fBMEMCACHED_SUCCESS\fP if
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all keys were successful. \fBMEMCACHED_NOTFOUND\fP will be return if no
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keys at all were found.
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\fI\%memcached_fetch_result()\fP sets error
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to \fBMEMCACHED_END\fP upon successful conclusion.
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\fBMEMCACHED_NOTFOUND\fP will be return if no keys at all were found.
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To find out more information please check:
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\fI\%http://libmemcached.org/\fP
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\fImemcached(1)\fP \fIlibmemcached(3)\fP \fImemcached_strerror(3)\fP
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2011-2012, Brian Aker DataDifferential, http://datadifferential.com/
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