[jira] [Created] (IGNITE-18931) Sql. Invalid expression code generation for comparing the results of a non-deterministic function.

["Pavel Pereslegin (Jira)" <ji...@apache.org>]

Pavel Pereslegin created IGNITE-18931:
-----------------------------------------

             Summary: Sql. Invalid expression code generation for comparing the results of a non-deterministic function.
                 Key: IGNITE-18931
                 URL: https://issues.apache.org/jira/browse/IGNITE-18931
             Project: Ignite
          Issue Type: Improvement
          Components: sql
            Reporter: Pavel Pereslegin


Currently expressions like "expr() = expr()" and "expr() != expr()" for non-deterministic functions (for example rand_uuid()) do not work correctly.

The problem seems to be related to the optimization made in RexProgramBuilder#registerInternal, ignoring the fact that the function is non-deterministic.

{code:java}
final RexSimplify simplify =
        new RexSimplify(rexBuilder, RelOptPredicateList.EMPTY, RexUtil.EXECUTOR);
    expr = simplify.simplifyPreservingType(expr);
{code}

This optimization translates comparison
{{<>($t1, $t1)}}
to 
{{CAST(AND(null, IS NULL($t1))):BOOLEAN NOT NULL}}

And it looks like a naive fix would be to apply this optimization only if {{RexUtil.isDeterministic(rexNode)}} returns true.

{{RexProgramBuilder}} currently is not a part of Ignite-3 codebase and it seems that it will be better to do such fix in Apache Calcite.

However, before doing this, we need to learn the discussions that have been made on this topic previously.

https://issues.apache.org/jira/browse/CALCITE-2823
https://issues.apache.org/jira/browse/CALCITE-3760
https://issues.apache.org/jira/browse/CALCITE-2142
https://issues.apache.org/jira/browse/CALCITE-2638
https://issues.apache.org/jira/browse/CALCITE-3531
https://issues.apache.org/jira/browse/CALCITE-4256



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