# Query on VDS not accelerated - manually querying parents IS accelerated

**URL:** https://community.dremio.com/t/query-on-vds-not-accelerated-manually-querying-parents-is-accelerated/7223
**Category:** Uncategorized
**Created:** [March 31, 2021, 10:14am UTC](https://community.dremio.com/t/query-on-vds-not-accelerated-manually-querying-parents-is-accelerated/7223 "2021-03-31T10:14:28Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![Saltxwater](https://avatars.discourse-cdn.com/v4/letter/s/94ad74/32.png) [@Saltxwater](https://community.dremio.com/u/Saltxwater)
#### Post date: [March 31, 2021, 10:14am UTC](https://community.dremio.com/t/query-on-vds-not-accelerated-manually-querying-parents-is-accelerated/7223/1 "2021-03-31T10:14:28Z")

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Hi!

I’ve got a Physical Dataset (A) with an aggregate reflection on dimension columns d1, d2 and aggregate (SUM) columns a1, a2, …, a750. (Also a raw reflection on this).  
I’ve got another PDS (B) with columns c1, c2, c3 with a raw reflection.  
I’ve separately got a Virtual Dataset which joins A with B on columns d1 = c1. (many to 1).

Using an external client (python) if I query the VDS with a WHERE clause on c2 (which should give me a subset of A) [and summing the a1 - a750 cols] then I see in the jobs that this query is not being accelerated by the aggr reflection on A (considered, not matched.) and is instead hitting the raw reflection on A. This query takes 220 seconds.

If with the same client I don’t query the VDS and instead query A and B directly, specifying the same join and WHERE on the same column then it DOES hit the aggregate reflection on A and the query completes in 40 seconds.

Is this behaviour explainable? I was surprised as I thought the query on the VDS would still optimise in the same way.

Thanks for your help

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### Author: ![balaji.ramaswamy](https://sea2.discourse-cdn.com/flex020/user_avatar/community.dremio.com/balaji.ramaswamy/32/843_2.png) [@balaji.ramaswamy](https://community.dremio.com/u/balaji.ramaswamy)
#### Post date: [April 1, 2021, 7:28am UTC](https://community.dremio.com/t/query-on-vds-not-accelerated-manually-querying-parents-is-accelerated/7223/2 "2021-04-01T07:28:35Z")

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@Saltxwater Are you able to send us the profile of the query that was not accelerated?

> **[How To Share A Query Profile](https://www.dremio.com/tutorials/share-query-profile-dremio/)**
>
> Tutorial explaining how to share a query profile in Dremio.