[
https://issues.apache.org/jira/browse/IMPALA-92?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Jim Apple updated IMPALA-92:
----------------------------
Attachment: (was: like-predicate.cc.patch)
> Significant performance difference between LIKE = 'x' AND = 'x'
> ---------------------------------------------------------------
>
> Key: IMPALA-92
> URL: https://issues.apache.org/jira/browse/IMPALA-92
> Project: IMPALA
> Issue Type: Bug
> Affects Versions: Impala 0.6
> Reporter: Philip Zeyliger
> Assignee: Skye Wanderman-Milne
> Fix For: Impala 0.7
>
> Attachments: like-predicate.cc.patch
>
>
> I'm running the following two queries. The only difference between them is
> I'm using "LIKE" in one case and "=" in another, though there is no "%" in
> the LIKE, so the effect is the same. I was surprised to see approximately a
> 10x difference in performance between them.
> {code}
> Query: select v1, c, count(*) FROM xxx b, yyy a WHERE a.v1 = b.file AND v5
> LIKE "hostId" AND v3 = "hosts" GROUP BY v1, c ORDER BY count(*) limit 1000
> Returned 89 row(s) in 10.13s
> Query: select v1, c, count(*) FROM xxx b, yyy a WHERE a.v1 = b.file AND v5
> LIKE "hostId" AND v3 = "hosts" GROUP BY v1, c ORDER BY count(*) limit 1000
> Returned 89 row(s) in 93.76s
> {code}
> I'm running
> {code}
> impalad version 0.6 RELEASE (build e675301a90e370f694d700b395a13f0265b7f09c)
> {code}
> I've attached the two query profiles. The basic difference is in the
> execution rate:
> {code}
> - Averaged Fragment 2:(1m27s 0.00%)
> - completion times: min:1m19s max:1m32s mean: 1m28s stddev:4s545ms
> - execution rates: min:35.33 MB/sec max:41.00 MB/sec mean:37.37 MB/sec
> stddev:1.90 MB/sec
> + - RowsReturnedRate: 9.00 /sec
> + Averaged Fragment 2:(7s906ms 0.00%)
> + completion times: min:7s620ms max:9s495ms mean: 8s056ms stddev:653ms
> + execution rates: min:342.95 MB/sec max:436.42 MB/sec mean:409.84
> MB/sec stddev:31.25 MB/sec
> {code}
> Obviously I've fixed my query.
--
This message was sent by Atlassian JIRA
(v6.3.15#6346)
