Ubuntu Manpage: memcached_append - Appending to or Prepending Data

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Provided by: libmemcached-dev_1.1.4-1.1build3_amd64

NAME

       memcached_append - Appending to or Prepending Data

SYNOPSIS

       #include <libmemcached-1.0/memcached.h>
              Compile and link with -lmemcached

       memcached_return_t  memcached_prepend(memcached_st  *ptr,  const char *key, size_t key_length, const char
       *value, size_t value_length, time_t expiration, uint32_t flags)

       memcached_return_t memcached_append(memcached_st *ptr, const char *key,  size_t  key_length,  const  char
       *value, size_t value_length, time_t expiration, uint32_t flags)

       memcached_return_t    memcached_prepend_by_key(memcached_st   *ptr,   const   char   *group_key,   size_t
       group_key_length, const char *key, size_t key_length, const  char  *value,  size_t  value_length,  time_t
       expiration, uint32_t flags)

       memcached_return_t    memcached_append_by_key(memcached_st    *ptr,   const   char   *group_key,   size_t
       group_key_length, const char *key, size_t key_length, const  char  *value,  size_t  value_length,  time_t
       expiration, uint32_t flags)

              Parameters

                     • ptr -- pointer to an initialized memcached_st struct

                     • group_key -- key namespace

                     • group_key_length -- length of the key namespace without any terminating zero

                     • key -- the key

                     • key_length -- length of the key without any terminating zero

                     • value -- the value to append/prepend

                     • value_length -- the length of the value without any terminating zero

                     • expiration -- expiration as a unix timestamp or as relative expiration time in seconds

                     • flags -- 16 bit flags

              Returns
                     memcached_return_t indicating success

DESCRIPTION

memcached_prepend() and memcached_append are used to modify information on a server. All methods take a
key, and key_length to store the object. Keys are currently limited to 250 characters when using either a
version of memcached which is 1.4 or below, or when using the text protocol. You must supply both a value
and a length. Optionally you may set an expiration time for the object and a 16 bit value (it is meant to
be used as a bitmap). flags is a 4 byte space that is stored along the main value. Many sub libraries
make use of this field, so in most cases users should avoid making use of it.

memcached_prepend() places a segment of data before the last piece of data stored. Currently expiration
and key are not used in the server.

memcached_append() places a segment of data at the end of the last piece of data stored. Currently
expiration and key are not used in the server.

memcached_prepend_by_key() and memcached_append_by_key() methods both behave in a similar manner as the
non key methods. The difference is that they use their group_key parameter to map objects to particular
servers.

If you are looking for performance, memcached_set() with non-blocking IO is the fastest way to store data
on the server.

All of the above functions are tested with the MEMCACHED_BEHAVIOR_USE_UDP behavior enabled. However, when
using these operations with this behavior on, there are limits to the size of the payload being sent to
the server. The reason for these limits is that the Memcached Server does not allow multi-datagram
requests and the current server implementation sets a datagram size to 1400 bytes. Due to protocol
overhead, the actual limit of the user supplied data is less than 1400 bytes and depends on the protocol
in use as, well as the operation being executed. When running with the binary protocol,
MEMCACHED_BEHAVIOR_BINARY_PROTOCOL, the size of the key,value, flags and expiry combined may not exceed
1368 bytes. When running with the ASCII protocol, the exact limit fluctuates depending on which function
is being executed and whether the function is a cas operation or not. For non-cas ASCII set operations,
there are at least 1335 bytes available to split among the key, key_prefix, and value; for cas ASCII
operations there are at least 1318 bytes available to split among the key, key_prefix and value. If the
total size of the command, including overhead, exceeds 1400 bytes, a MEMCACHED_WRITE_FAILURE will be
returned.

RETURN VALUE

       All methods return a value of type memcached_return_t. On success the value will be MEMCACHED_SUCCESS.

       Use memcached_strerror() to translate this value to a printable string.

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DESCRIPTION

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SEE ALSO