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https://issues.apache.org/jira/browse/HIVE-23095?focusedWorklogId=415863&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-415863
]
ASF GitHub Bot logged work on HIVE-23095:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 04/Apr/20 00:59
Start Date: 04/Apr/20 00:59
Worklog Time Spent: 10m
Work Description: prasanthj commented on pull request #964: HIVE-23095
ndv 70
URL: https://github.com/apache/hive/pull/964#discussion_r403398547
##########
File path:
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/common/ndv/hll/HLLSparseRegister.java
##########
@@ -148,8 +148,12 @@ public int encodeHash(long hashcode) {
}
}
- public int getSize() {
- return sparseMap.size() + tempListIdx;
+ public boolean isSizeGreaterThan(int s) {
+ if (sparseMap.size() + tempListIdx > s) {
+ mergeTempListToSparseMap();
Review comment:
The tempList array was added for insertion performance (at the cost of
slight misestimation when there are duplicates in the temp list) to quickly
buffer up 1024 elements. This is negating that by merging it to sparse map more
frequently. We might as well add it to sparse map directly instead of tempList
so that getSize() becomes a constant time operation. The sparse register will
switch to dense around after 3200 elements so sparsemap will not be a hot loop.
I would recommend removing tempList from sparse register that way there will be
less branching.
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Issue Time Tracking
-------------------
Worklog Id: (was: 415863)
Time Spent: 20m (was: 10m)
> NDV might be overestimated for a table with ~70 value
> -----------------------------------------------------
>
> Key: HIVE-23095
> URL: https://issues.apache.org/jira/browse/HIVE-23095
> Project: Hive
> Issue Type: Bug
> Reporter: Zoltan Haindrich
> Assignee: Zoltan Haindrich
> Priority: Major
> Labels: pull-request-available
> Attachments: HIVE-23095.01.patch, HIVE-23095.02.patch,
> HIVE-23095.03.patch, HIVE-23095.04.patch, HIVE-23095.04.patch,
> HIVE-23095.04.patch
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> uncovered during looking into HIVE-23082
> https://issues.apache.org/jira/browse/HIVE-23082?focusedCommentId=17067773&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-17067773
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