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Memcache

The memcache function provides a memory cache per stream worker. If it has replicas (@Instances("N")), then this cache is per all instances of the stream worker. It is similar to cache, but this function has a time-to-live (ttl) parameter.

Features​

The following functions are allowed:

  • memcache:get("key") - gets a value per given key
  • memcache:put("key", "value") - puts "key" and "value", returns a value that saves into a cache
  • memcache:put("key", "value", ttl) - puts "key" and "value" with ttl, returns a value that saves into a cache. ttl is set by default 5000L (5 seconds)

Syntax​

Memcache uses the following syntax:

memcache:get(<String> key) 
memcache:put(<String> key, <String> value, <Long> ttl)

Example​

– Event triggers
CREATE TRIGGER EventsPutTrigger WITH (interval=1 sec);

CREATE TRIGGER EventsGetTrigger WITH (interval=5 sec);

– Event stores
CREATE TABLE put_in_cache(value_is_put string);

CREATE TABLE get_from_cache(value string);

@info(name = 'put-query')
INSERT INTO put_in_cache
SELECT memcache:put("my key", "my value", 10000L) as value_is_put
FROM EventsPutTrigger;

@info(name = 'get-query')
INSERT INTO get_from_cache
SELECT memcache:get("my key") as value
FROM EventsGetTrigger;

Following document is saved every second in put_in_cache with a 10-second ttl.

        {"value_is_put": "true"}

Following document is saved every five seconds in get_from_cache.

        {"value": "my_value"}