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https://issues.apache.org/jira/browse/HIVE-17536?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16168751#comment-16168751
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Vineet Garg commented on HIVE-17536:
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This is for queries without from e.g. {{select 1}}. getBasicStats return -1 and
then {{estimateRowSizeFromSchema}} isn't able to estimate since there is no
data so we end up returning -1. Previously on countering 0 number of rows we
were instead returning 1.
One way of handling this is to change getNumRows to return 1 instead of -1.
> StatsUtil::getBasicStatForTable doesn't distinguish b/w absence of statistics
> or zero stats
> -------------------------------------------------------------------------------------------
>
> Key: HIVE-17536
> URL: https://issues.apache.org/jira/browse/HIVE-17536
> Project: Hive
> Issue Type: Improvement
> Components: Statistics
> Reporter: Vineet Garg
> Assignee: Vineet Garg
> Attachments: HIVE-17536.1.patch, HIVE-17536.2.patch
>
>
> This method returns zero for both of the following cases:
> * Statistics are missing in metastore
> * Actual stats e.g. number of rows are zero
> It'll be good for this method to return e.g. -1 in absence of statistics
> instead of assuming it to be zero.
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