[
https://issues.apache.org/jira/browse/DERBY-3937?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12645333#action_12645333
]
Martin Hajduch commented on DERBY-3937:
---------------------------------------
Ok, in the meantime I read more about the topic and Derby.
So back to my original question - is there any alternative to COUNT(*) and
implementing of paging over ordered set of (milion) rows with constant
performance towards 'last' pages ?
If not at the moment - is there any development planned in this area (where I
could possibly contribute as well) ?
If not, is there any development planned in the area of speeding up the index
scan so that milion rows do not take 10, but let's say 1 second ? Even such
constant improvement would help in my particular case.
I tried several open source databases, found Derby to be the closest to my
needs and I am able to devote some resources in this direction - but would like
to get some pointers towards what to concentrate on to.
> Select count(*) scans all the rows (and is therefore slow with big tables),
> is the amount of rows not available/known for example in index ?
> --------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-3937
> URL: https://issues.apache.org/jira/browse/DERBY-3937
> Project: Derby
> Issue Type: Improvement
> Components: Performance
> Environment: Any
> Reporter: Martin Hajduch
>
> Create table with 5000000 rows. Create index on unique ID. Select count(*) on
> such table is going to take quite some time.
> Shouldn't the index contain amount of indexed rows and the value taken from
> there ?
> Additionally, queries of the form select count(*) from table where
> col1=value; take lots of time (depending on amount of rows satisfying WHERE
> clause) even if index on col1 exists. Isn't it possible to find first and
> last occurence in the index, and then calculate amount of rows more
> effectively then scanning through all of them ?
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
