Github user vdiravka commented on a diff in the pull request:
https://github.com/apache/drill/pull/937#discussion_r138133454
--- Diff:
contrib/storage-hive/core/src/main/codegen/templates/ObjectInspectorHelper.java
---
@@ -204,7 +204,11 @@ public static JBlock getDrillObject(JCodeModel m,
ObjectInspector oi,
<#elseif entry.hiveType == "TIMESTAMP">
JVar tsVar =
jc._else().decl(m.directClass(java.sql.Timestamp.class.getCanonicalName()),
"ts",
castedOI.invoke("getPrimitiveJavaObject").arg(returnValue));
- jc._else().assign(returnValueHolder.ref("value"),
tsVar.invoke("getTime"));
+ // Bringing relative timestamp value without timezone info to
timestamp value in UTC, since Drill keeps date-time values in UTC
--- End diff --
I'm not fully agreed. Let me explain:
Let's take for example TimeStampVector, Drill keeps date-time values in
DrillBuf as millis from epoch. Then timestamp values are extracted via
[getObject()](https://github.com/apache/drill/blob/1c09c2f13bd0f50ca40c17dc0bfa7aae5826b8c3/exec/java-exec/src/main/codegen/templates/FixedValueVectors.java#L446)
method (I agree that the code in this method is questionable, but it is not
current issue, this jira contains other bug).
For PST timezone machine and query `select timestamp '1970-01-01
00:00:00' from (VALUES(1))` the `0 millis` timestamp value is stored in
DrillBuf and only on extracting stage the value is represented with server
timezone. The same result for querying the timestamp data from any data source:
'1970-01-01 00:00:00' will be stored as `0 millis` timestamp for any timezone.
But only for hive functions the logic differs:
Let's consider `select to_utc_timestamp('1969-12-31 16:00:00','PST') from
(VALUES(1))`. The result should be "1970-01-01 00:00:00" even with current
Drill date/time logic.
The output from hive's UDF is "java.sql.Timestamp" value (for PST timezone
machine -- `28800000 millis` internally, for UTC timezone machine -- `0 millis`
internally). But in favour of above logic of
[getObject()](https://github.com/apache/drill/blob/1c09c2f13bd0f50ca40c17dc0bfa7aae5826b8c3/exec/java-exec/src/main/codegen/templates/FixedValueVectors.java#L446)
the `0 millis` timestamp value should be storing in the DrillBuf for any
timezone.
In the result, with my fix the same timestamp values will be stored in
DrillBuf for any timezone machine.
Let me know if I am wrong with something.
---
