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From "Paul Rogers (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DRILL-4763) Parquet file with DATE logical type produces wrong results for simple SELECT
Date Mon, 04 Jul 2016 18:02:11 GMT
Paul Rogers created DRILL-4763:
----------------------------------

             Summary: Parquet file with DATE logical type produces wrong results for simple
SELECT
                 Key: DRILL-4763
                 URL: https://issues.apache.org/jira/browse/DRILL-4763
             Project: Apache Drill
          Issue Type: Bug
          Components: Execution - Data Types
    Affects Versions: 1.6.0
            Reporter: Paul Rogers


Created a simple Parquet file with the following schema:

message test { required int32 index; required int32 value (DATE); required int32 raw; }

That is, a file with an int32 storage type and a DATE logical type. Then, created a number
of test values:

0 (which should be interpreted as 1970-01-01) and
(int) (System.currentTimeMillis() / (24*60*60*1000) ) Which should be interpreted as the number
of days since 1970-01-01 and today.

According to the Parquet spec (https://github.com/Parquet/parquet-format/blob/master/LogicalTypes.md),
Parquet dates are expressed as "the number of days from the Unix epoch, 1 January 1970."

Java timestamps are expressed as "measured in milliseconds, between the current time and midnight,
January 1, 1970 UTC."

There is ambiguity here: Parquet dates are presumably local times not absolute times, so the
math above will actually tell us the date in London right now, but that's close enough.

Generate the local file to date.parquet. Query it with:

SELECT * from `local`.`root`.`date.parquet`;

The results are incorrect:

index value raw
1	-11395-10-18T00:00:00.000-07:52:58	0

Here, we have a value of 0. The displayed date is decidedly not 1970-01-01T00:00:00. We actually
have many problems:

1. The date is far off.
2. The output shows time. But, the Parquet DATE format explcitly does NOT include time, so
it makes no sense to include it.
3. The output attempts to show a time zone, but a time zone of -07:52:58, while close to PST,
is not right (there is no timezine that is of by 7:02 from UTC.)
4. The data has no time zone, Parquet DATE explicilty is a local time, so it is impossible
to know the relationship between that date an UTC.

The correct output (in ISO format) would be: 1970-01-01

The last line should be today's date, but instead is:

6	-11348-04-20T00:00:00.000-07:52:58	16986

Expected:

2016-07-04

Note that all the information to produce the right information is available to Drill:

1. The DATE annotation says the meaning of the signed 32-bit integer.
2. Given the starting point and duration in days, the conversion to Drill's own internal date
format is unambiguous.
3. The DATE annotation says that the date is local, so Drill should not attempt to convert
to UTC. (That is, a Java Date object can't be used, instead a Joda/Java 8 LocalDate is necessary.)





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