Getting confused with caching 101

Question

Okay, I've been going round and round with this for hours now.
My search page can take several minutes to run, so I want to put a cahe on the search results, so a user can select a record, go look at it, and come back again without waiting a couple more minutes to re-run the query.
I made the region "Cached by user", a timeout of 6 hours, and the condition is Item 1 = Item 2. The values are P3_USE_CACHED_SEARCH and Y.
Several processes are set to change the value of :P3_USE_CACHED_SEARCH depending on if the criteria for the search changes. However when I run it, I get various results. The worst result is if I click my CLEAR button, which fires off a APEX_UTIL.CACHE_PURGE_BY_PAGE. It seems that once I do this, the cache never gets populated again. I can run numerous searches, select a record, come back, and with DEBUG on, I see a message that no region is cached so it does a dynamic refresh of the region again.
I'm probably missing something extremely simple (it always seems that way), so I'm going to try an re-create this on apex.oracle.com. The worst that will happen is by re-creating this behaviour there, it will all work correctly and I'll see what I'm doing wrong.
The workspace is wbfergus
id and password are both htmldb (lowercase)
The app is 26115 (the one in the middle). This is a small subset without most of the functionality and it will probably take me an hour or two to get the new code modified in that app. It's currently about 11:00 MST in Denver, so around 1:00pm I should either have the behaviour duplicated, or have figured out what I'm doing wrong.
Thanks,
Bill Ferguson

Answer 1

Hi Arie,
The cache condition is used to determine both reading and writing to cache. If your cache condition is false, the page/region will be rendered dynamically – not reading from cache – and in the same time, the new content will not be written to the cache.
I just ran across that in the docs also (I think). The doc states "Cache Condition Type - Select a condition type from the list. If the condition returns false, the region is rendered dynamically and is not be cached. If the condition returns true, the region is cached."
So, my logic was flawed from the beginning. I was interpreting the cache condition incorrectly. I thought it was a flag condition on whether or not to use the cached contents. It seems strange (to me at least), that if you want to use caching, and have taken the steps to activate the caching, that your flag condition would not only decide whether to use the cache or not, but at the same time tell Apex whether or not to cache those newer results. So it behaves as a condition for two different decisions, not just for one decision.
I'm trying to go back through my two pages now (the calling page with the search criteria and the popup) to see if I can implement this new strategy.
So what I need to do now is if the query/search changes, clear the cache and always leave my cache condition set to true (I always want to cache the results for the "Records Found" region). Just sometimes though, like when the search criteria has changed, I want to clear the cache before the region is displayed so there is nothing to retrieve and hopefully the region will render dynamically.
I think I have all that understood now, so off to trying to get this dual logic figured out.
Thanks,
Bill Ferguson