I am looking at the documentation for the expire field in the cache tables and the documentation in CacheBackendInterface.php says:
One of the following values:
- CacheBackendInterface::CACHE_PERMANENT: Indicates that the item should not be removed unless it is deleted explicitly.
- A Unix timestamp: Indicates that the item will be considered invalid after this time, i.e. it will not be returned by
$allow_invalidhas been set to
TRUE. When the item has expired, it may be permanently deleted by the garbage collector at any time.
When I look in a cache table, for example cache_render, I see that many entries have NULL in the expire column and I noticed it only get clear on a complete cache clear, such as after running
What does a null value set for the expire column in a cache table mean?