Roel Hartman has followed up my post by doing the due diligence and testing the performance of different APEX condition types. His findings back up what I just asserted. (But I wasn't just guessing, my assertions were based on facts I learned long ago from someone in the APEX team via the Oracle APEX forum - so long ago that I cannot now find the conversation!)
As I said previously, for a more complex condition than "item=value" you will often have to use a PL/SQL expression condition, and that's fine. However, it is not uncommon to see a page where there is a group of several items that all have the same complex condition. For example, perhaps if some complex condition is true then we need to collect the user's bank details and contact details - maybe 12 items. The same complex condition is applied (and has to be evaluated) for each of the 12 items. In this sort of case it may be appropriate to add child regions to the form region, and apply the complex condition just once - to the child region that contains this group of conditional items. A suitable region template (perhaps even "no template") can be applied to these new child regions so that the appearance of the page is not changed by adding them.
Example 1: original page
Region: My Form- Item: Name
- Item: Date of Birth
- Item: Bank Account No (complex condition)
- Item: Bank Sort Code (complex condition)
...
- Item: Address Line 1 (complex condition)
- Item: Address Line 2 (complex condition)
...
- Item: Something else
Example 2: page using child regions
Region: My Form- Subregion: Personal Details
-- Item: Name
-- Item: Date of Birth
- Subregion: Bank and Address details (complex condition)
-- Item: Bank Account No
-- Item: Bank Sort Code
...
-- Item: Address Line 1
-- Item: Address Line 2
...
- Subregion: More stuff
-- Item: Something else
Example 2 achieves the same result as Example 1 but only evaluates the complex condition once instead of many times. As well as improving performance this also makes your page simpler: if the condition changes in the future you only have one instance to change.
