Re: jira question

[Satheesh Bandaram]

I think it is possible to avoid extra storage with generated columns too.  These generated columns need not necessarily be in physical storage. The language layer could evaluate the _expression_ on the fly when requested. Again, if a query uses an _expression_ that might match a generated column, it would be possible to use the index. It is possible to have a first implementation actually create the column in physical storage and then improve the implementation to avoid this physical column and instead just evaluate the _expression_ when needed. Satheesh Manish Khettry wrote: Adding hidden columns is an easy way to implement the feature but it does result in storage being wasted. Mike's suggestion (option 3) in Jira seems to be a better way of doing it. As I understand it, Mike is suggesting that the store is unaware of the fact that a function value is used as a key in the btree for theindex. The language layer maintains the information and uses it to maintain the index (i.e. passing the right key value in DML and index build after applying the function) as well as considering the index if the function is present in the query. Manish On 7/29/05, Satheesh Bandaram <[EMAIL PROTECTED]> wrote: I don't know why Jira is not forwarding comments for this specific bug. Here are some of my comments. SQL standard provides a way to have generated columns. These generated columns can be created using, GENERATED ALWAYS AS <left paren><value _expression_><right paren> Once we have a generated column, it should be possible to create a regular B-Tree index on this generated column. I think there are several advantages of using this syntax: 1) It is standards based. 2) Since the column is visible, it is much cleaner and easier to understand the semantics 3) Fits nicely with existing syntax for identity columns. I think this is a good enhancement to add to Derby. Satheesh Mike Matrigali wrote: don' know what is going on with jira. I have added comments on 455, and have not seen those go to the list. Rick Hillegas wrote: I added comments to two bugs this week (171 and 455) and was hoping that Jira would post these comments to the developer's list. In particular, I was hoping that my comment on 455 (_expression_ indexes) would invite further discussion by the Store experts. Alas, Jira did not post my comments. Would appreciate theories about how I am mis-using Jira. Thanks, -Rick