On 02.02.2012 11:14, Kristian Waagan wrote:
On 01.02.2012 14:51, Rick Hillegas wrote:
< snip>
On 2/1/12 4:07 AM, Simon Chatelain wrote:
< snip>
You may want to set derby.storage.indexStats.log=true, and more
importantly, derby.storage.indexStats.debug.trace=true. Run you app
for a while, then grep for "{istat}" in derby.log.
This will tell you if automatic calculation is being triggered.
Although strongly discouraged for production environments, you can try
to set lndiffThreshold to zero, or a very small value, to schedule an
update on every occasion, i.e. when you compile a statement like
"select ... from tbl where indexed_column = ?".
If you want to test this manually, you will appreciate setting
derby.storage.indexStats.debug.absdiffThreshold, and possibly
derby.storage.indexStats.debug.createThreshold, to a lower value (both
express number of rows, defaults are 1000 and 250 respectively).
Just for reference, testing stuff like this in ij can be done along
these lines:
select * from sys.sysstatistics (note creationtimestamp / statistics,
may want a join to get table name)
insert into ... (or delete from ...)
prepare q as 'select * from <table> where <indexed_column> = ?'
select * from sys.sysstatistics
--
Kristian
Note that the istat daemon will only be triggered when the table
changes in size. If you do updates that changes the index key
distribution significantly you'll want to generate new statistics
manually/periodically.
Regards,
