Cache API

Functions that affect only the cache. More...

Functions
ssize_t	nmdb_cache_get (nmdb_t *db, const unsigned char *key, size_t ksize, unsigned char *val, size_t vsize)
	Get the value associated with a key from cache.
int	nmdb_cache_set (nmdb_t *db, const unsigned char *key, size_t ksize, const unsigned char *val, size_t vsize)
	Set the value associated with a key, but only in the cache.
int	nmdb_cache_del (nmdb_t *db, const unsigned char *key, size_t ksize)
	Delete a key, but only from the cache.
int	nmdb_cache_cas (nmdb_t *db, const unsigned char *key, size_t ksize, const unsigned char *oldval, size_t ovsize, const unsigned char *newval, size_t nvsize)
	Perform an atomic compare-and-swap only on the cache.
int	nmdb_cache_incr (nmdb_t *db, const unsigned char *key, size_t ksize, int64_t increment, int64_t *newval)
	Atomically increment the value associated with a key only in the cache.

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Detailed Description

Functions that affect only the cache.

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Function Documentation

ssize_t nmdb_cache_get	(	nmdb_t *	db,
		const unsigned char *	key,
		size_t	ksize,
		unsigned char *	val,
		size_t	vsize
	)

Get the value associated with a key from cache.

This is just like nmdb_get(), except it only queries the caches, and never the database.

Parameters:

	db	connection instance.
	key	the key.
	ksize	the key size.
[out]	val	buffer where the value will be stored.
	vsize	size of the value buffer.

Returns:

the size of the value written to the given buffer, -1 if the key is not in the cache, or -2 if there was an error.

int nmdb_cache_set	(	nmdb_t *	db,
		const unsigned char *	key,
		size_t	ksize,
		const unsigned char *	val,
		size_t	vsize
	)

Set the value associated with a key, but only in the cache.

This command sets the key's value in the cache, but does NOT affect the backend database. Combining it with nmdb_set() and/or nmdb_set_sync() is not recommended, because consistency issues may arise.

Parameters:

	db	connection instance.
	key	the key.
	ksize	the key size.
	val	the value
	vsize	size of the value.

Returns:

1 on success, < 0 on error.

int nmdb_cache_del	(	nmdb_t *	db,
		const unsigned char *	key,
		size_t	ksize
	)

Delete a key, but only from the cache.

This command deletes a key from the cache, but does NOT affect the backend database. Combining it with nmdb_del() and/or nmdb_del_sync() is not recommended, because consistency issues may arise.

Parameters:

	db	connection instance.
	key	the key.
	ksize	the key size.

Returns:

1 on success, < 0 on error.

int nmdb_cache_cas	(	nmdb_t *	db,
		const unsigned char *	key,
		size_t	ksize,
		const unsigned char *	oldval,
		size_t	ovsize,
		const unsigned char *	newval,
		size_t	nvsize
	)

Perform an atomic compare-and-swap only on the cache.

This command works just like nmdb_cas(), except it affects only the cache, and not the backend database. Equivalent to atomically doing:

if get_cache(key) == oldval, then set_cache(key, newval)

Parameters:

	db	connection instance.
	key	the key.
	ksize	the key size.
	oldval	the old, expected value.
	ovsize	size of the expected value.
	newval	the new value to set.
	nvsize	size of the new value.

Returns:

2 on success, 1 if the current value does not match oldval, 0 if the key is not in the database, or < 0 on error.

int nmdb_cache_incr	(	nmdb_t *	db,
		const unsigned char *	key,
		size_t	ksize,
		int64_t	increment,
		int64_t *	newval
	)

Atomically increment the value associated with a key only in the cache.

This command works just like nmdb_incr(), except it affects only the cache, and not the backend database.

Parameters:

	db	connection instance.
	key	the key.
	ksize	the key size.
	increment	the value to add to the current one (can be negative).
[out]	newval	pointer to an integer that will be set to the new value.

Returns:

2 if the increment was successful, 1 if the current value was not in an appropriate format, 0 if the key is not in the database, or < 0 on error.