[jira] [Created] (CALCITE-4911) CAST operation should throw an exception when cast DECIMAL type lose significant digits

["duan xiong (Jira)" <ji...@apache.org>]

duan xiong created CALCITE-4911:
-----------------------------------

             Summary: CAST operation should throw an exception when cast DECIMAL type lose significant digits
                 Key: CALCITE-4911
                 URL: https://issues.apache.org/jira/browse/CALCITE-4911
             Project: Calcite
          Issue Type: Bug
    Affects Versions: 1.28.0
            Reporter: duan xiong


In Calcite:
{code:java}
select avg(comm) as a from "scott".emp{code}
This SQL physical plan is:
{noformat}
EnumerableProject(A=[CAST(/(CAST(CASE(=($1, 0), null:DECIMAL(19, 2), $0)):DECIMAL(7, 2), $1)):DECIMAL(7, 2)])
  EnumerableAggregate(group=[{}], agg#0=[$SUM0($6)], agg#1=[COUNT($6)])
    EnumerableTableScan(table=[[scott, EMP]]){noformat}
As above:
The Calcite tries to cast DECIMAL(19,2) to DECIMAL(7,2). Actually, this cast should throw an exception but not.

According to SQL Standard's description about <CAST specification>:

If TD is exact numeric, then
Case:
a) If SD is exact numeric or approximate numeric, then
Case:
i) If there is a representation of SV in the data type *TD that does not lose any leading significant digits* after rounding or truncating if necessary, then TV is that representation. The choice of whether to round or truncate is implementation-defined.
ii) Otherwise, {*}an exception condition is raised{*}: data exception------numeric value out of range.



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