[GitHub] [calcite] MusbahELFIL opened a new pull request #1286: CALCITE-3155 : Fixing bug in the unparse of UNION_ALL SqlSetOperator when it has no operands

[GitBox <gi...@apache.org>]

MusbahELFIL opened a new pull request #1286: CALCITE-3155 : Fixing bug in the unparse of UNION_ALL SqlSetOperator when it has no operands
URL: https://github.com/apache/calcite/pull/1286
 
 
   when we have a query of the form "select X from TEST_TABLE where Y= ( select Z from TEST-TABLE2 where 1=2), when converting to a RelNode, the plan contains a LogicalValues with no tuples (which is correct since the right hand side should return no tuples).
   
   When converting the above RelNode to an SqlNode the LogicalValues is being converted to a UNION_ALL operator with no operands. Its toString() method which is called when doing an unparse (when converting the generated SqlNode back to an SQL string) is throwing an exception (since it has no tuples).
   
   The fix converts the values with no tuples to a "select NULL, NULL ... from DUAL"

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