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From Tyler Hobbs <>
Subject Re: Slow down of secondary index query with VNODE (C* version 1.2.18, jre6).
Date Fri, 19 Sep 2014 21:10:21 GMT
On Fri, Sep 19, 2014 at 12:41 PM, Jay Patel <> wrote:

> Btw, there is no data in the table. Table is empty. Query is fired on the
> empty table.

This is actually the worst case for secondary index lookups.

> From the tracing ouput, I don't understand why it's doing multiple scans
> on one node. With non-vnode, there is only one scan per node & same query
> works fine.
> If you look at the output1.txt attached earlier, coordinator is firing
> index scan on a given node (for example, in the below snippet
> from output1.txt) multiple times for different token ranges. Why can't it
> fire only one time? With non-vnode, it's only one time & query comes back
> very fast.

It will merge requests to neighboring ranges when the same node is a
replica for both of them.  Without vnodes, this usually results in all
ranges for a node being merged.  With vnodes, merging still happens, but
not all ranges can be merged.

Tyler Hobbs
DataStax <>

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