Author: Attila Jeges <firstname.lastname@example.org>
Date: Wed Feb 8 19:44:16 2017 +0100
IMPALA-2716: Hive/Impala incompatibility for timestamp data in Parquet
Before this change:
Hive adjusts timestamps by subtracting the local time zone's offset
from all values when writing data to Parquet files. Hive is internally
inconsistent because it behaves differently for other file formats. As
a result of this adjustment, Impala may read "incorrect" timestamp
values from Parquet files written by Hive.
After this change:
Impala reads Parquet MR timestamp data and adjusts values using a time
zone from a table property (parquet.mr.int96.write.zone), if set, and
will not adjust it if the property is absent. No adjustment will be
applied to data written by Impala.
New HDFS tables created by Impala using CREATE TABLE and CREATE TABLE
LIKE <file> will set the table property to UTC if the global flag
--set_parquet_mr_int96_write_zone_to_utc_on_new_tables is set to true.
HDFS tables created by Impala using CREATE TABLE LIKE <other table>
will copy the property of the table that is copied.
This change also affects the way Impala deals with
--convert_legacy_hive_parquet_utc_timestamps global flag (introduced
IMPALA-1658). The flag will be taken into account only if
parquet.mr.int96.write.zone table property is not set and ignored
Reviewed-by: Dan Hecht <email@example.com>
Tested-by: Impala Public Jenkins