Revert "apache#420: Support for not_eq predicate in pruning predicates (

apache#544)"

This reverts commit 2568323.

datafusion/src/physical_optimizer/pruning.rs

@@ -552,14 +552,6 @@ fn build_predicate_expression(
     };
     let corrected_op = expr_builder.correct_operator(op);
     let statistics_expr = match corrected_op {
-        Operator::NotEq => {
-            // column != literal => (min, max) = literal => min > literal || literal > max
-            let min_column_expr = expr_builder.min_column_expr()?;
-            let max_column_expr = expr_builder.max_column_expr()?;
-            min_column_expr
-                .gt(expr_builder.scalar_expr().clone())
-                .or(expr_builder.scalar_expr().clone().gt(max_column_expr))
-        }
         Operator::Eq => {
             // column = literal => (min, max) = literal => min <= literal && literal <= max
             // (column / 2) = 4 => (column_min / 2) <= 4 && 4 <= (column_max / 2)
@@ -937,26 +929,6 @@ mod tests {
         Ok(())
     }
 
-    #[test]
-    fn row_group_predicate_not_eq() -> Result<()> {
-        let schema = Schema::new(vec![Field::new("c1", DataType::Int32, false)]);
-        let expected_expr = "#c1_min Gt Int32(1) Or Int32(1) Gt #c1_max";
-
-        // test column on the left
-        let expr = col("c1").not_eq(lit(1));
-        let predicate_expr =
-            build_predicate_expression(&expr, &schema, &mut RequiredStatColumns::new())?;
-        assert_eq!(format!("{:?}", predicate_expr), expected_expr);
-
-        // test column on the right
-        let expr = lit(1).not_eq(col("c1"));
-        let predicate_expr =
-            build_predicate_expression(&expr, &schema, &mut RequiredStatColumns::new())?;
-        assert_eq!(format!("{:?}", predicate_expr), expected_expr);
-
-        Ok(())
-    }
-
     #[test]
     fn row_group_predicate_gt() -> Result<()> {
         let schema = Schema::new(vec![Field::new("c1", DataType::Int32, false)]);