[jira] [Created] (FLINK-15602) Blink planner does not respect the precision when casting timestamp to varchar

[Shang Yuanchun (Jira)]

Dawid Wysakowicz created FLINK-15602:
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             Summary: Blink planner does not respect the precision when casting timestamp to varchar
                 Key: FLINK-15602
                 URL: https://issues.apache.org/jira/browse/FLINK-15602
             Project: Flink
          Issue Type: Bug
          Components: Table SQL / Planner
    Affects Versions: 1.10.0
            Reporter: Dawid Wysakowicz
             Fix For: 1.10.0


According to SQL 2011 Part 2 Section 6.13 General Rules 11) d)

{quote}
If SD is a datetime data type or an interval data type then let Y be the shortest character string that
conforms to the definition of <literal> in Subclause 5.3, “<literal>”, and such that the interpreted value
of Y is SV and the interpreted precision of Y is the precision of SD.
{quote}

That means:
{code}
select cast(cast(TO_TIMESTAMP('2014-07-02 06:14:00', 'YYYY-MM-DD HH24:mm:SS') as TIMESTAMP(0)) as VARCHAR(256)) from ...;
// should produce
// 2014-07-02 06:14:00

select cast(cast(TO_TIMESTAMP('2014-07-02 06:14:00', 'YYYY-MM-DD HH24:mm:SS') as TIMESTAMP(3)) as VARCHAR(256)) from ...;
// should produce
// 2014-07-02 06:14:00.000

select cast(cast(TO_TIMESTAMP('2014-07-02 06:14:00', 'YYYY-MM-DD HH24:mm:SS') as TIMESTAMP(9)) as VARCHAR(256)) from ...;
// should produce
// 2014-07-02 06:14:00.000000000
{code}

One possible solution would be to propagate the precision in {{org.apache.flink.table.planner.codegen.calls.ScalarOperatorGens#localTimeToStringCode}}. If I am not mistaken this problem was introduced in [FLINK-14599]



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