[GitHub] [doris] englefly commented on a diff in pull request #15466: [Bug](filter) fix not in(null) return true

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

englefly commented on code in PR #15466:
URL: https://github.com/apache/doris/pull/15466#discussion_r1059645378


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be/src/vec/exec/scan/vscan_node.cpp:
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@@ -771,6 +771,13 @@ Status VScanNode::_normalize_not_in_and_not_eq_predicate(VExpr* expr, VExprConte
                         ->get_function_state(FunctionContext::FRAGMENT_LOCAL));
         HybridSetBase::IteratorBase* iter = state->hybrid_set->begin();
         auto fn_name = std::string("");
+
+        // not in(any, null) == (x!=any and x!=null)
+        // (x!=null)=null=false, so not in(any, null) return always false

Review Comment:
   `in (any, null)` does not always return false, in fact, it returns `null`.
   an counter example:
   `k not in (null)` returns null, so `not ( k not in (null)` returns null.
   `select * from t where k not in (null) ` returns empty result set.
   `select * from t where not (k not in (null)) ` returns empty result set too.



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