db-derby-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Harshvardhan Gupta (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (DERBY-6938) Obtain cardinality estimates and true estimates for base tables as well as for intermediate results for queries involving multiple joins.
Date Sat, 10 Jun 2017 20:38:19 GMT

     [ https://issues.apache.org/jira/browse/DERBY-6938?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Harshvardhan Gupta updated DERBY-6938:
--------------------------------------
    Attachment: explain.txt

Hi Bryan,

I am attaching the explain plan of one of the queries from the dataset. I have doubts with
regard to the scans performed for INFO_TYPE and TITLE tables and optimizer's estimated row
count for those scans.

How in general is the estimated row count for scans as part of joins determined? 

I went through the link below but they do not cover the case when a join is specified 
http://db.apache.org/derby/docs/10.13/tuning/ctunstats849203.html


>  Obtain cardinality estimates and true estimates for base tables as well as for intermediate
results for queries involving multiple joins. 
> -------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-6938
>                 URL: https://issues.apache.org/jira/browse/DERBY-6938
>             Project: Derby
>          Issue Type: Sub-task
>          Components: SQL
>            Reporter: Harshvardhan Gupta
>            Assignee: Harshvardhan Gupta
>         Attachments: explain.txt
>
>




--
This message was sent by Atlassian JIRA
(v6.3.15#6346)

Mime
View raw message