Zoltán Borók-Nagy created IMPALA-11322:
------------------------------------------
Summary: Add proper estimations for virtual columns
Key: IMPALA-11322
URL: https://issues.apache.org/jira/browse/IMPALA-11322
Project: IMPALA
Issue Type: Bug
Components: Frontend
Reporter: Zoltán Borók-Nagy
IMPALA-801 adds support for virtual column INPUT__FILE__NAME.
Though memory estimations are a bit off for virtual columns because the default
estimations are used. Virtual columns actually require much less memory. E.g.
INPUT__FILE__NAME is only allocated per file per scanner.
Also cardinality estimations are off. These could be problematic if users do
GROUP BY based on virtual columns, because currently we overestimate the
cardinality. This causes too high memory estimations. As a workaround, users
can set MEM_LIMIT.
--
This message was sent by Atlassian Jira
(v8.20.7#820007)
