Vova Vysotskyi created DRILL-7490:
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Summary: limit is not pushed to JDBC storage plugin
Key: DRILL-7490
URL: https://issues.apache.org/jira/browse/DRILL-7490
Project: Apache Drill
Issue Type: Bug
Components: Client - JDBC
Affects Versions: 1.11.0
Reporter: Vova Vysotskyi
Assignee: Vova Vysotskyi
The limit is not pushed to JDBC storage plugin.
The following query:
{code:sql}
select person_id from mysql.`drill_mysql_test`.person limit 10
{code}
Returns plan:
{noformat}
00-00 Screen
00-01 Project(person_id=[$0])
00-02 SelectionVectorRemover
00-03 Limit(fetch=[10])
00-04 Limit(fetch=[10])
00-05 Jdbc(sql=[SELECT `person_id` FROM
`drill_mysql_test`.`person` ])
{noformat}
This issue happens since incorrect row count is calculated for {{JdbcSort}}.
Drill enforces to use {{RelNode.estimateRowCount(mq)}} for calculating row
count for all inheritants of {{Sort}} rel node (see {{DrillRelMdRowCount}}),
but {{JdbcSort}} doesn't override this method and uses parent one which returns
row count of input. So planner choses {{DrillLimitRel}} since it has less row
count.
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