[jira] [Commented] (CALCITE-3504) allow empty ARRAY[] literals

[Pressenna (Jira)]

    [ 
https://issues.apache.org/jira/browse/CALCITE-3504?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17190047#comment-17190047
 ] 

Pressenna commented on CALCITE-3504:
------------------------------------

Current internal solution: default to {{null}} component type for empty arrays.
We created a new subclass of SqlArrayValueConstructor, which caters for empty 
arrays accordingly and registered it against the operator table.

See subclass below.

{code:java}
  public static class SqlArrayValueConstructorAllowingEmpty
          extends SqlArrayValueConstructor {
    @Override
    protected RelDataType getComponentType(
            RelDataTypeFactory typeFactory, List<RelDataType> argTypes) {
      if (argTypes.isEmpty()) {
        return typeFactory.createSqlType(SqlTypeName.NULL);
      }
      return super.getComponentType(typeFactory, argTypes);
    }

    @Override
    public boolean checkOperandTypes(SqlCallBinding callBinding, boolean 
throwOnFailure) {
      if (callBinding.operands().isEmpty()) {
        return true;
      }
      return super.checkOperandTypes(callBinding, throwOnFailure);
    }
  }
{code}

> allow empty ARRAY[] literals
> ----------------------------
>
>                 Key: CALCITE-3504
>                 URL: https://issues.apache.org/jira/browse/CALCITE-3504
>             Project: Calcite
>          Issue Type: Wish
>    Affects Versions: 1.21.0
>            Reporter: Pressenna
>            Priority: Major
>
> Currently an ARRAY expression requires at least one element.
> Please allow empty ARRAY expressions.
> {code:sql}
> SELECT ARRAY[] FROM foo;
> -- or more concise for updates:
> UPDATE food set array_column = ARRAY[];
> {code}



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