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Re: Odd Row Estimates in Query Plan (rows=75)

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On 08/15/2018 01:03 PM, Don Seiler wrote:
Here's the query, obfuscated manually by me:

SELECT
         'Foo' as system_function,
stores.name <http://stores.name> as store,
         lt.owner,
         lt.minute_of_day,
         lt.records
         FROM
         foo.stores
         LEFT OUTER JOIN
             (SELECT
                 lts.store_pkey,
                 lts.owner,
                 date_trunc('minute', lts.date_gifted) as minute_of_day,
                 count(*) as records
             FROM foo.gifts lts
             WHERE
                 lts.date_added  > '2017-07-14 11:13:05'
             AND lts.date_added  < '2017-08-13 14:14:21'
             AND lts.date_gifted >= '2017-08-13 11:13:05'
             AND lts.date_gifted <  '2017-08-13 14:14:21'
             GROUP BY 1,2,3
             ORDER BY 1
             ) lt ON lt.store_pkey = stores.pkey
         WHERE lt.records IS NOT NULL;

The foo.gifts table is pretty much the core table of our database. It's big and very active. There is an index on date_added but not yet on date_gifted.

I'm working to re-write the query while the dev sees if we even need this query anymore.


I agree the issue seems to be in the index/filter of the dates. That leads me to another question:

Why in:

WHERE
	lts.date_added  > '2017-07-14 11:13:05'
AND
	lts.date_added  < '2017-08-13 14:14:21'
AND
	lts.date_gifted >= '2017-08-13 11:13:05'
AND
	lts.date_gifted <  '2017-08-13 14:14:21'

is

	lts.date_added  > '2017-07-14 11:13:05'

and
	
	lts.date_gifted >= '2017-08-13 11:13:05'
?

In other words one '>' and the other '>=' ?








--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx




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