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.TH "MEMCACHED_APPEND_BY_KEY" "3" "April 09, 2011" "0.47" "libmemcached"
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memcached_append_by_key \- Storing and Replacing Data
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.\" Man page generated from reStructeredText.
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#include <libmemcached/memcached.h>
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.B memcached_return_t memcached_set (memcached_st *ptr, const char *key, size_t key_length, const char *value, size_t value_length, time_t expiration, uint32_t flags);
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.B memcached_return_t memcached_add (memcached_st *ptr, const char *key, size_t key_length, const char *value, size_t value_length, time_t expiration, uint32_t flags);
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.B memcached_return_t memcached_replace (memcached_st *ptr, const char *key, size_t key_length, const char *value, size_t value_length, time_t expiration, uint32_t flags);
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.B memcached_return_t memcached_prepend(memcached_st\fI\ *ptr\fP, const char\fI\ *key\fP, size_t\fI\ key_length\fP, const char\fI\ *value\fP, size_t\fI\ value_length\fP, time_t\fI\ expiration\fP, uint32_t\fI\ flags\fP)
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.B memcached_return_t memcached_append(memcached_st\fI\ *ptr\fP, const char\fI\ *key\fP, size_t\fI\ key_length\fP, const char\fI\ *value\fP, size_t\fI\ value_length\fP, time_t\fI\ expiration\fP, uint32_t\fI\ flags\fP)
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.B memcached_return_t memcached_cas(memcached_st *ptr, const char *key, size_t key_length, const char *value, size_t value_length, time_t expiration, uint32_t flags, uint64_t cas);
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.B memcached_return_t memcached_set_by_key(memcached_st *ptr, const char *master_key, size_t master_key_length, const char *key, size_t key_length, const char *value, size_t value_length, time_t expiration, uint32_t flags);
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.B memcached_return_t memcached_add_by_key(memcached_st *ptr, const char *master_key, size_t master_key_length, const char *key, size_t key_length, const char *value, size_t value_length, time_t expiration, uint32_t flags);
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.B memcached_return_t memcached_replace_by_key(memcached_st *ptr, const char *master_key, size_t master_key_length, const char *key, size_t key_length, const char *value, size_t value_length, time_t expiration, uint32_t flags);
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.B memcached_return_t memcached_prepend_by_key(memcached_st *ptr, const char *master_key, size_t master_key_length, const char *key, size_t key_length, const char *value, size_t value_length, time_t expiration, uint32_t flags);
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.B memcached_return_t memcached_append_by_key(memcached_st *ptr, const char *master_key, size_t master_key_length, const char *key, size_t key_length, const char *value, size_t value_length, time_t expiration, uint32_t flags);
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.B memcached_return_t memcached_cas_by_key(memcached_st *ptr, const char *master_key, size_t master_key_length, const char *key, size_t key_length, const char *value, size_t value_length, time_t expiration, uint32_t flags, uint64_t cas);
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Compile and link with \-lmemcached
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memcached_set(), memcached_add(), and memcached_replace() are all used to
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store information on the server. All methods take a key, and its length to
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store the object. Keys are currently limited to 250 characters by the
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memcached(1) server. You must also supply a value and a length. Optionally you
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may tests an expiration time for the object and a 16 byte value (it is
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meant to be used as a bitmap).
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memcached_set() will write an object to the server. If an object already
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exists it will overwrite what is in the server. If the object does not exist
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it will be written. If you are using the non\-blocking mode this function
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will always return true unless a network error occurs.
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memcached_replace() replaces an object on the server. If the object is not
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found on the server an error occurs.
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memcached_add() adds an object to the server. If the object is found on the
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server an error occurs, otherwise the value is stored.
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memcached_prepend() places a segment of data before the last piece of data
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stored. Currently expiration and key are not used in the server.
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memcached_append() places a segment of data at the end of the last piece of
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data stored. Currently expiration and key are not used in the server.
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memcached_cas() overwrites data in the server as long as the "cas" value is
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still the same in the server. You can get the cas value of a result by
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calling memcached_result_cas() on a memcached_result_st(3) structure. At the point
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that this note was written cas is still buggy in memached. Turning on tests
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for it in libmemcached(3) is optional. Please see memcached_set() for
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information on how to do this.
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memcached_set_by_key(), memcached_add_by_key(), memcached_replace_by_key(),
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memcached_prepend_by_key(), memcached_append_by_key_by_key(),
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memcached_cas_by_key() methods all behave in a similar method as the non key
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methods. The difference is that they use their master_key parameter to map
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objects to particular servers.
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If you are looking for performance, memcached_set() with non\-blocking IO is
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the fastest way to store data on the server.
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All of the above functions are testsed with the \fBMEMCACHED_BEHAVIOR_USE_UDP\fPbehavior enabled. But when using these operations with this behavior on, there
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are limits to the size of the payload being sent to the server. The reason for
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these limits is that the Memcahed Server does not allow multi\-datagram requests
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and the current server implementation sets a datagram size to 1400 bytes. Due
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to protocol overhead, the actual limit of the user supplied data is less than
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1400 bytes and depends on the protocol in use as well as the operation being
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executed. When running with the binary protocol, \(ga\(ga MEMCACHED_BEHAVIOR_BINARY_PROTOCOL\(ga\(ga,
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the size of the key,value, flags and expiry combined may not exceed 1368 bytes.
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When running with the ASCII protocol, the exact limit fluctuates depending on
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which function is being executed and whether the function is a cas operation
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or not. For non\-cas ASCII set operations, there are at least 1335 bytes available
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to split among the key, key_prefix, and value; for cas ASCII operations there are
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at least 1318 bytes available to split among the key, key_prefix and value. If the
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total size of the command, including overhead, exceeds 1400 bytes, a \fBMEMCACHED_WRITE_FAILURE\fPwill be returned.
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All methods return a value of type \fBmemcached_return_t\fP.
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On success the value will be \fBMEMCACHED_SUCCESS\fP.
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Use memcached_strerror() to translate this value to a printable string.
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For memcached_replace() and memcached_add(), \fBMEMCACHED_NOTSTORED\fP is a
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legitmate error in the case of a collision.
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To find out more information please check:
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\fI\%https://launchpad.net/libmemcached\fP
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memcached(1) libmemached(3) memcached_strerror(3)
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2011, Brian Aker DataDifferential, http://datadifferential.com/
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