fix(joblist): MCOL-6218 null safe operator now handles string literals for a specific edge case.

Author: mariadb-KristinaPavlova

dbcon/execplan/simplecolumn.h

@@ -337,6 +337,10 @@ class SimpleColumn : public ReturnedColumn
   double getDoubleVal(rowgroup::Row& row, bool& isNull) override
   {
     evaluate(row, isNull);
+    if (isNull)
+    {
+      return 0;
+    }
     return TreeNode::getDoubleVal();
   }
 

mysql-test/columnstore/basic/r/mcol-6218.result

@@ -0,0 +1,17 @@
+DROP DATABASE IF EXISTS mcol6218;
+CREATE DATABASE mcol6218;
+USE mcol6218;
+CREATE TABLE person (
+name VARCHAR(100) NOT NULL,
+surname VARCHAR(100) DEFAULT NULL
+) ENGINE=Columnstore
+DEFAULT CHARSET=utf8mb3
+COLLATE=utf8mb3_general_ci;
+INSERT INTO person (name, surname) VALUES
+('Warren Baby', NULL),
+('Charlie', 'Parker'),
+('Oscar', 'Peterson');
+SELECT * FROM person WHERE surname <=> 1;
+name	surname
+drop table person;
+DROP DATABASE mcol6218;

mysql-test/columnstore/basic/t/mcol-6218.test

@@ -0,0 +1,26 @@
+-- source ../include/have_columnstore.inc
+
+--disable_warnings
+DROP DATABASE IF EXISTS mcol6218;
+--enable_warnings
+
+CREATE DATABASE mcol6218;
+
+USE mcol6218;
+
+CREATE TABLE person (
+  name VARCHAR(100) NOT NULL,
+  surname VARCHAR(100) DEFAULT NULL
+) ENGINE=Columnstore
+DEFAULT CHARSET=utf8mb3
+COLLATE=utf8mb3_general_ci;
+ 
+INSERT INTO person (name, surname) VALUES
+  ('Warren Baby', NULL),
+  ('Charlie', 'Parker'),
+  ('Oscar', 'Peterson');
+ 
+SELECT * FROM person WHERE surname <=> 1;
+
+drop table person;
+DROP DATABASE mcol6218;