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https://issues.apache.org/jira/browse/HIVE-22239?focusedWorklogId=324951&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-324951
]
ASF GitHub Bot logged work on HIVE-22239:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 08/Oct/19 08:47
Start Date: 08/Oct/19 08:47
Worklog Time Spent: 10m
Work Description: kgyrtkirk commented on pull request #787: HIVE-22239
URL: https://github.com/apache/hive/pull/787#discussion_r332377711
##########
File path:
standalone-metastore/metastore-common/src/main/thrift/hive_metastore.thrift
##########
@@ -562,14 +562,27 @@ struct DateColumnStatsData {
5: optional binary bitVectors
}
+struct Timestamp {
+1: required i64 secondsSinceEpoch
Review comment:
I'm afraid that there will be a downside that we are throwing away precision
- and because of that we may get into some troubles later:
If we do truncate to seconds; we may not be able to extend the timestamp
logic to the stats optimizer - as we are not working with the real values.
consider the following
```sql
select '2019-11-11 11:11:11.400' < '2019-11-11 11:11:11.300'
```
if we round to seconds; consider that the left side comes from a table - a
the columns maxvalue; the stats optimizer could deduce a "true" for the above
Would it complicate things much to use a non-rounded timestamp - and retain
miliseconds/microsendond as well ?
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Issue Time Tracking
-------------------
Worklog Id: (was: 324951)
Time Spent: 1h 50m (was: 1h 40m)
> Scale data size using column value ranges
> -----------------------------------------
>
> Key: HIVE-22239
> URL: https://issues.apache.org/jira/browse/HIVE-22239
> Project: Hive
> Issue Type: Improvement
> Components: Physical Optimizer
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
> Priority: Major
> Labels: pull-request-available
> Attachments: HIVE-22239.01.patch, HIVE-22239.02.patch,
> HIVE-22239.patch
>
> Time Spent: 1h 50m
> Remaining Estimate: 0h
>
> Currently, min/max values for columns are only used to determine whether a
> certain range filter falls out of range and thus filters all rows or none at
> all. If it does not, we just use a heuristic that the condition will filter
> 1/3 of the input rows. Instead of using that heuristic, we can use another
> one that assumes that data will be uniformly distributed across that range,
> and calculate the selectivity for the condition accordingly.
> This patch also includes the propagation of min/max column values from
> statistics to the optimizer for timestamp type.
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