[jira] [Created] (SPARK-30203) store assignable if there exists an appropriate user-defined cast function

["Kent Yao (Jira)" <ji...@apache.org>]

Kent Yao created SPARK-30203:
--------------------------------

             Summary: store assignable if there exists an appropriate user-defined cast function
                 Key: SPARK-30203
                 URL: https://issues.apache.org/jira/browse/SPARK-30203
             Project: Spark
          Issue Type: Sub-task
          Components: SQL
    Affects Versions: 3.0.0
            Reporter: Kent Yao


h3. 9.2 Store assignment
h4. Syntax Rules

1) Let T be the TARGET and let V be the VALUE in an application of the Syntax Rules of this Subclause.
 2) Let TD and SD be the declared types of T and V, respectively.
 3) If TD is character string, binary string, numeric, boolean, datetime, interval, or a user-defined type, then
 either SD shall be assignable to TD or there shall exist an appropriate user-defined cast function UDCF
 from SD to TD.
 _NOTE 319 — “Appropriate user-defined cast function” is defined in Subclause 4.11, “Data conversions”_
h3.  4.11 Data conversions

Implicit type conversion can occur in expressions, fetch operations, single row select operations, inserts, deletes,
and updates. Explicit type conversions can be specified by the use of the CAST operator.

 

The current implementation for ANSI store assignment is totally out of context. 

According to this rule, `there shall exist an appropriate user-defined cast function UDCF`, the spark legacy store assignment is just fine because we do have *a_ppropriate cast_* _*functions.*_

At least according to the ansi cast rule, the current ANSI assignment policy is too strict to the ANSI cast rules

 
{code:java}
* (SD) --------------------- (TD) -------------------------
*     | EN  AN  C  D  T  TS  YM  DT  BO  UDT  B  RT  CT  RW
* EN  |  Y   Y  Y  N  N   N   M   M   N   M   N   M   N   N
* AN  |  Y   Y  Y  N  N   N   N   N   N   M   N   M   N   N
*  C  |  Y   Y  Y  Y  Y   Y   Y   Y   Y   M   N   M   N   N
*  D  |  N   N  Y  Y  N   Y   N   N   N   M   N   M   N   N
*  T  |  N   N  Y  N  Y   Y   N   N   N   M   N   M   N   N
* TS  |  N   N  Y  Y  Y   Y   N   N   N   M   N   M   N   N
* YM  |  M   N  Y  N  N   N   Y   N   N   M   N   M   N   N
* DT  |  M   N  Y  N  N   N   N   Y   N   M   N   M   N   N
* BO  |  N   N  Y  N  N   N   N   N   Y   M   N   M   N   N
* UDT |  M   M  M  M  M   M   M   M   M   M   M   M   M   N
*  B  |  N   N  N  N  N   N   N   N   N   M   Y   M   N   N
* RT  |  M   M  M  M  M   M   M   M   M   M   M   M   N   N
* CT  |  N   N  N  N  N   N   N   N   N   M   N   N   M   N
* RW  |  N   N  N  N  N   N   N   N   N   N   N   N   N   M
*
* Where:
* EN = Exact Numeric
* AN = Approximate Numeric
* C = Character (Fixed- or Variable-Length, or Character Large Object)
* D = Date
* T = Time
* TS = Timestamp
* YM = Year-Month Interval
* DT = Day-Time Interval
* BO = Boolean
* UDT = User-Defined Type
* B = Binary (Fixed- or Variable-Length or Binary Large Object)
* RT = Reference type
* CT = Collection type
* RW = Row type
{code}
 

 

_cc [~cloud_fan] [~gengliang]_ [~maropu] 

 



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