Re: [jira] Updated: (DERBY-805) Push join predicates into union and other set operations. DERBY-649 implemented scalar (single table) predicate pushdown. Adding join predicate push down could improve performance significantly.

[Army]

Andrew McIntyre wrote:

The only time the statistics for an index are guaranteed to be up to
date is when the index is created. See:

https://issues.apache.org/jira/browse/DERBY-737
https://issues.apache.org/jira/browse/DERBY-269

Creating the index before loading the table with data means that the
statistics for the table will correspond to an empty table. The table
needs to be loaded with data, and then the index created afterward.

Thanks for asking the question about indexes, Bryan.  And thanks to Andrew for 
answering the question and for providing Jira entries.  I've included the above 
text as a footnote in the latest html document for DERBY-805 (_v5.html).

And many thanks to both of you for taking the time to read this rather daunting 
document; I do appreciate the feedback...

Army