Incrementing and Decrementing Values

SYNOPSIS

#include <libmemcached/memcached.h>
Compile and link with -lmemcached
memcached_return_t memcached_increment(memcached_st *ptr, const char *key, size_t key_length, uint32_t offset, uint64_t *value)
memcached_return_t memcached_decrement(memcached_st *ptr, const char *key, size_t key_length, uint32_t offset, uint64_t *value)
memcached_return_t memcached_increment_with_initial(memcached_st *ptr, const char *key, size_t key_length, uint64_t offset, uint64_t initial, time_t expiration, uint64_t *value)
memcached_return_t memcached_decrement_with_initial(memcached_st *ptr, const char *key, size_t key_length, uint64_t offset, uint64_t initial, time_t expiration, uint64_t *value)
memcached_return_t memcached_increment_by_key(memcached_st *ptr, const char *group_key, size_t group_key_length, const char *key, size_t key_length, uint32_t offset, uint64_t *value)
memcached_return_t memcached_decrement_by_key(memcached_st *ptr, const char *group_key, size_t group_key_length, const char *key, size_t key_length, uint32_t offset, uint64_t *value)
memcached_return_t memcached_increment_with_initial_by_key(memcached_st *ptr, const char *group_key, size_t group_key_length, const char *key, size_t key_length, uint64_t offset, uint64_t initial, time_t expiration, uint64_t *value)
memcached_return_t memcached_decrement_with_initial_by_key(memcached_st *ptr, const char *group_key, size_t group_key_length, const char *key, size_t key_length, uint64_t offset, uint64_t initial, time_t expiration, uint64_t *value)
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
  • offset -- offset to increment/decrement
  • initial -- initial value if key does not exist and expiration is not MEMCACHED_EXPIRATION_NOT_ADD
  • expiration -- expiration as a unix timestamp or as relative expiration time in seconds
  • value -- the resulting value after initialization/increment/decrement
Returns:

memcached_return_t indicating success

DESCRIPTION

memcached(1) servers have the ability to increment and decrement keys (overflow and underflow are not detected). This gives you the ability to use memcached to generate shared sequences of values.

memcached_increment() takes a key and key_length and increments the value by the offset passed to it. The value is then returned via the uint32_t value pointer you pass to it.

memcached_decrement() takes a key and key_length and decrements the value by the offset passed to it. The value is then returned via the uint32_t value pointer you pass to it.

memcached_increment_with_initial() takes a key and key_length and increments the value by the offset passed to it. If the object specified by key does not exist, one of two things may happen: If the expiration value is MEMCACHED_EXPIRATION_NOT_ADD, the operation will fail. For all other expiration values, the operation will succeed by seeding the value for that key with a initial value to expire with the provided expiration time. The flags will be set to zero. The value is then returned via the uint32_t value pointer you pass to it. memcached_increment_with_initial is only available when using the binary protocol.

memcached_decrement_with_initial() takes a key and key_length and decrements the value by the offset passed to it. If the object specified by key does not exist, one of two things may happen: If the expiration value is MEMCACHED_EXPIRATION_NOT_ADD, the operation will fail. For all other expiration values, the operation will succeed by seeding the value for that key with a initial value to expire with the provided expiration time. The flags will be set to zero. The value is then returned via the uint32_t value pointer you pass to it. memcached_decrement_with_initial() is only available when using the binary protocol.

memcached_increment_by_key(), memcached_decrement_by_key(), memcached_increment_with_initial_by_key(), and memcached_decrement_with_initial_by_key() are master key equivalents of the above.

RETURN VALUE

A value of type memcached_return_t is returned. On success that value will be MEMCACHED_SUCCESS. Use memcached_strerror() to translate this value to a printable string.