Usage of new Update function about cache_tab HOT 4 CLOSED

ets_cache:update(graph_cache,123,#graph{id = 123 , val=2342},fun() -> ok end)

from cache_tab.

The Val should be in the form of {ok, V} or error. If existing value in the cache matches Val then UpdateFun is not called. Otherwise UpdateFun is called and should return ok (otherwise the cache will not be updated).
Example 1: you want to write value a at key 1:

ets_cache:update(my_tab, 1, {ok, a}, fun() -> database_write(1, a), ok end).

In the example above database_write(1, a) is not called if there is already value a associated with the key 1.
Example 2: you want to delete value b associated with key 2:

ets_cache:update(my_tab, 2, error, fun() -> database_delete(2), ok end).

In this case function database_delete(2) won't be called if there is already error in the cache (i.e. 'miss' is associated with key 2 in the cache).

from cache_tab.

So, simply put, ets_cache:update() function serves two purposes:

1. Writing/deleting database data with cache updates.
2. Avoiding excessive writes/deletes of the same data.

from cache_tab.

Great .. and thanks @zinid

from cache_tab.