On Mon, 02 Dec 2019 10:36:36 +0900 (JST) Tatsuo Ishii <is...@sraoss.co.jp> wrote:
> >> One thing pending in this development line is how to catalogue aggregate > >> functions that can be used in incrementally-maintainable views. > >> I saw a brief mention somewhere that the devels knew it needed to be > >> done, but I don't see in the thread that they got around to doing it. > >> Did you guys have any thoughts on how it can be represented in catalogs? > >> It seems sine-qua-non ... > > > > Yes, this is a pending issue. Currently, supported aggregate functions are > > identified their name, that is, we support aggregate functions named > > "count", > > "sum", "avg", "min", or "max". As mentioned before, this is not robust > > because there might be user-defined aggregates with these names although all > > built-in aggregates can be used in IVM. > > > > In our implementation, the new aggregate values are calculated using "+" and > > "-" operations for sum and count, "/" for agv, and ">=" / "<=" for min/max. > > Therefore, if there is a user-defined aggregate on a user-defined type which > > doesn't support these operators, errors will raise. Obviously, this is a > > problem. Even if these operators are defined, the semantics of user-defined > > aggregate functions might not match with the way of maintaining views, and > > resultant might be incorrect. > > > > I think there are at least three options to prevent these problems. > > > > In the first option, we support only built-in aggregates which we know able > > to handle correctly. Supported aggregates can be identified using their > > OIDs. > > User-defined aggregates are not supported. I think this is the simplest and > > easiest way. > > I think this is enough for the first cut of IVM. So +1. If there is no objection, I will add the check of aggregate functions by this way. Thanks. Regards, Yugo Nagata -- Yugo Nagata <nag...@sraoss.co.jp>
