[
https://issues.apache.org/jira/browse/IMPALA-14417?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Pranav Yogi Lodha updated IMPALA-14417:
---------------------------------------
Description:
Currently, the JDBC external data source integration issues an additional count
estimation query in the prepare phase to estimate the number of rows in a JDBC
table. While this helps the planner choose a better parallelization strategy
for complex queries (e.g. joins or aggregations), it also introduces an extra
JDBC round trip.
To give users more control, we propose introducing a query option that enables
or disables row count estimation for JDBC tables. When enabled, Impala will
issue the count estimation query during prepare. When disabled, Impala will
skip this step, avoiding the additional JDBC round trip.
was:
Currently, the JDBC external data source integration issues an additional
COUNT(*) query in the {{prepare()}} phase to estimate the number of rows in a
JDBC table. While this helps the planner choose a better parallelization
strategy for complex queries (e.g. joins or aggregations), it also introduces
an extra JDBC round trip.
To give users more control, we propose introducing a query option that enables
or disables row count estimation for JDBC tables. When enabled, Impala will
issue the COUNT(*) query during prepare. When disabled, Impala will skip this
step, avoiding the additional JDBC round trip.
> Query option for JDBC row count estimation
> ------------------------------------------
>
> Key: IMPALA-14417
> URL: https://issues.apache.org/jira/browse/IMPALA-14417
> Project: IMPALA
> Issue Type: New Feature
> Reporter: Pranav Yogi Lodha
> Priority: Major
>
> Currently, the JDBC external data source integration issues an additional
> count estimation query in the prepare phase to estimate the number of rows in
> a JDBC table. While this helps the planner choose a better parallelization
> strategy for complex queries (e.g. joins or aggregations), it also introduces
> an extra JDBC round trip.
> To give users more control, we propose introducing a query option that
> enables or disables row count estimation for JDBC tables. When enabled,
> Impala will issue the count estimation query during prepare. When disabled,
> Impala will skip this step, avoiding the additional JDBC round trip.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
