Csaba Ringhofer created IMPALA-7557:
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Summary: Optimize local time functions for the UTC case
Key: IMPALA-7557
URL: https://issues.apache.org/jira/browse/IMPALA-7557
Project: IMPALA
Issue Type: Improvement
Components: Backend
Reporter: Csaba Ringhofer
Currently two flags decide whether to do UTZ->local timezone conversions
- convert_legacy_hive_parquet_utc_timestamps
- use_local_tz_for_unix_timestamp_conversions
Enabling these global flags make Impala more compatible with Hive, but can
highly degrade performance. Since IMPALA-7362, it is possible to override the
local timezone with a query option. Setting timezone to UTC practically
disables the flags above, but their overhead does not disappear completely. It
would be relatively easy to create shortcuts for the UTC case to avoid this
overhead.
This could make it easier to choose the right values for the flags: both could
be set to true, and users who want to avoid the performance impact could switch
to UTC.
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