ey-chih chow created SPARK-22639:
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Summary: no rowcount estimation returned if groupby clause
involves substring
Key: SPARK-22639
URL: https://issues.apache.org/jira/browse/SPARK-22639
Project: Spark
Issue Type: Bug
Components: Optimizer, SQL
Affects Versions: 2.2.0
Reporter: ey-chih chow
CBO can not estimate rowcount if the groupby clause of a query involves the
expression substring. For example, we can not estimate the row count of the
following query, extracted from TPC-DS queries and based on the TPC-DS schema:
SELECT item.`i_brand`, count(1), date_dim.`d_year`, item.`i_brand_id`,
sum(store_sales.`ss_ext_sales_price`) AS `ext_price`, item.`i_item_sk`
FROM store_sales INNER JOIN date_dim ON (date_dim.`d_date_sk` =
store_sales.`ss_sold_date_sk`) INNER JOIN item ON (store_sales.`ss_item_sk` =
item.`i_item_sk`)
GROUP BY item.`i_brand`, date_dim.`d_date`, substring(item.`i_item_desc`, 1,
30), date_dim.`d_year`, item.`i_brand_id`, item.`i_item_sk`
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