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.TH "MEMCACHED_MGET_EXECUTE_BY_KEY" "3" "June 17, 2011" "0.49" "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 *ptr, memcached_result_st *result, memcached_return_t *error);
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.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);
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.B memcached_return_t memcached_mget (memcached_st *ptr, const char * const *keys, const size_t *key_length, size_t number_of_keys);
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.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);
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.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);
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.B char * memcached_fetch (memcached_st *ptr, char *key, size_t *key_length, size_t *value_length, uint32_t *flags, memcached_return_t *error);
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.B memcached_return_t memcached_fetch_execute (memcached_st *ptr, memcached_execute_fn *callback, void *context, uint32_t number_of_callbacks);
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.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);
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.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);
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Compile and link with \-lmemcached
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memcached_get() is used to fetch an individual value from the server. You
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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 uint32_t pointer to contain whatever flags you stored with the value,
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a size_t pointer which will be filled with size of of the object, and a
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memcached_return_t pointer to hold any error. The object will be returned
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upon success and NULL will be returned on failure. Any object returned by
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memcached_get() must be released by the caller application.
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memcached_mget() is used to select multiple keys at once. For multiple key
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operations it is always faster to use this function. This function always
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works asynchronously. memcached_fetch() is then used to retrieve any keys
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found. No error is given on keys that are not found. You must call either
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memcached_fetch() or memcached_fetch_result() after a successful call to
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memcached_mget(). You should continue to call these functions until they
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return NULL (aka no more values). If you need to quit in the middle of a
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memcached_get() call, execute a memcached_quit(). After you do this, you can
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issue new queries against the server.
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memcached_fetch() is used to fetch an individual value from the server.
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memcached_mget() must always be called before using this method. You
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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 uint32_t pointer to contain whatever flags you stored with the value,
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a size_t pointer which will be filled with size of of the object, and a
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memcached_return_t pointer to hold any error. The object will be returned
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upon success and NULL will be returned on failure. \fBMEMCACHD_END\fP is
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returned by the *error value when all objects that have been found are
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returned. The final value upon \fBMEMCACHED_END\fP is null. Values
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returned by memcached_fetch() must be freed by the caller. memcached_fetch()
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will be DEPRECATED in the near future, memcached_fetch_result() should be
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memcached_fetch_result() is used to return a memcached_result_st(3) structure
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from a memcached server. The result object is forward compatible with changes
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to the server. For more information please refer to the memcached_result_st(3)
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help. This function will dynamically allocate a result structure for you
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if you do not pass one to the function.
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memcached_fetch_execute() is a callback function for result sets. Instead
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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 memcached_st that can be cloned for use in the called function (it can not
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be used directly). It also passes a result set which does not need to be freed.
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Finally it passes a "context". This is just a pointer to a memory reference
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you supply the calling function. Currently only one value is being passed
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to each function call. In the future there will be an option to allow this
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memcached_mget_execute() and memcached_mget_execute_by_key() is
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similar to memcached_mget(), but it may trigger the supplied callbacks
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with result sets while sending out the queries. If you try to perform
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a really large multiget with memcached_mget() you may encounter a
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deadlock in the OS kernel (it will fail to write data to the socket because
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the input buffer is full). memcached_mget_execute() solves this
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problem by processing some of the results before continuing sending
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out requests. Please note that this function is only available in the
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memcached_get_by_key() and memcached_mget_by_key() behave in a similar nature
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as memcached_get() and memcached_mget(). The difference is that they take
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a master key that is used for determining which server an object was stored
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if key partitioning was used for storage.
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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
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\fBMEMCACHED_NOT_SUPPORTED\fP being returned, or for those functions which do not return
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a \fBmemcached_return_t\fP, the error function parameter will be set to
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\fBMEMCACHED_NOT_SUPPORTED\fP.
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All objects returned must be freed by the calling application.
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memcached_get() and memcached_fetch() will return NULL on error. You must
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look at the value of error to determine what the actual error was.
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\fBmemcached_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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\fBmemcached_fetch()\fP and \fBmemcached_fetch_result()\fP set 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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MEMCACHED_KEY_TOO_BIG is set to error whenever memcached_fetch() was used
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and the key was set larger then MEMCACHED_MAX_KEY, which was the largest
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key allowed for the original memcached ascii server.
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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, Brian Aker DataDifferential, http://datadifferential.com/
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