fix: Avoid mistaken ILike to string equality optimization

Author: srh

datafusion/optimizer/src/simplify_expressions/expr_simplifier.rs

@@ -1606,8 +1606,9 @@ impl<S: SimplifyInfo> TreeNodeRewriter for Simplifier<'_, S> {
                                 }))
                             }
                             Some(pattern_str)
-                                if !pattern_str
-                                    .contains(['%', '_', escape_char].as_ref()) =>
+                                if !like.case_insensitive
+                                    && !pattern_str
+                                        .contains(['%', '_', escape_char].as_ref()) =>
                             {
                                 // If the pattern does not contain any wildcards, we can simplify the like expression to an equality expression
                                 // TODO: handle escape characters
@@ -4102,6 +4103,11 @@ mod tests {
         assert_eq!(simplify(expr), col("c1").like(lit("a_")));
         let expr = col("c1").not_like(lit("a_"));
         assert_eq!(simplify(expr), col("c1").not_like(lit("a_")));
+
+        let expr = col("c1").ilike(lit("a"));
+        assert_eq!(simplify(expr), col("c1").ilike(lit("a")));
+        let expr = col("c1").not_ilike(lit("a"));
+        assert_eq!(simplify(expr), col("c1").not_ilike(lit("a")));
     }
 
     #[test]