[Enhancement](doris-future) Support REGR_ARGX, REGR_ARGY, REGR_COUNT and REGR_R2 aggregate functions (#61352)

Issue Number: #38974, #38976

Related PR: #55940

Problem Summary:

This PR completes the remaining statistical regression aggregate
functions (`REGR_*`) by adding support for `REGR_AVGX`, `REGR_AVGY`,
`REGR_COUNT`, and `REGR_R2`, based on the unified Regr aggregate
function
  approach introduced in #55940.

Author: JoverZhang

be/src/exprs/aggregate/aggregate_function_regr.cpp

@@ -0,0 +1,93 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include "exprs/aggregate/aggregate_function_regr.h"
+
+#include "core/data_type/data_type.h"
+#include "core/data_type/define_primitive_type.h"
+#include "exprs/aggregate/aggregate_function.h"
+#include "exprs/aggregate/aggregate_function_simple_factory.h"
+#include "exprs/aggregate/factory_helpers.h"
+#include "exprs/aggregate/helpers.h"
+
+namespace doris {
+
+template <RegrFunctionKind kind>
+AggregateFunctionPtr create_aggregate_function_regr(const std::string& name,
+                                                    const DataTypes& argument_types,
+                                                    const DataTypePtr& result_type,
+                                                    const bool result_is_nullable,
+                                                    const AggregateFunctionAttr& attr) {
+    assert_arity_range(name, argument_types, 2, 2);
+    DCHECK(argument_types[0]->get_primitive_type() == TYPE_DOUBLE);
+    DCHECK(argument_types[1]->get_primitive_type() == TYPE_DOUBLE);
+    if constexpr (kind == RegrFunctionKind::regr_count) {
+        DCHECK(result_type->get_primitive_type() == TYPE_BIGINT);
+        DCHECK(!result_is_nullable);
+    } else {
+        DCHECK(result_type->get_primitive_type() == TYPE_DOUBLE);
+        DCHECK(result_is_nullable);
+    }
+
+    bool y_nullable_input = argument_types[0]->is_nullable();
+    bool x_nullable_input = argument_types[1]->is_nullable();
+    if (y_nullable_input) {
+        if (x_nullable_input) {
+            return creator_without_type::create_ignore_nullable<
+                    AggregateFunctionRegr<TYPE_DOUBLE, kind, true, true>>(argument_types,
+                                                                          result_is_nullable, attr);
+        } else {
+            return creator_without_type::create_ignore_nullable<
+                    AggregateFunctionRegr<TYPE_DOUBLE, kind, true, false>>(
+                    argument_types, result_is_nullable, attr);
+        }
+    } else {
+        if (x_nullable_input) {
+            return creator_without_type::create_ignore_nullable<
+                    AggregateFunctionRegr<TYPE_DOUBLE, kind, false, true>>(
+                    argument_types, result_is_nullable, attr);
+        } else {
+            return creator_without_type::create_ignore_nullable<
+                    AggregateFunctionRegr<TYPE_DOUBLE, kind, false, false>>(
+                    argument_types, result_is_nullable, attr);
+        }
+    }
+}
+
+void register_aggregate_function_regr(AggregateFunctionSimpleFactory& factory) {
+    factory.register_function_both(RegrTraits<RegrFunctionKind::regr_avgx>::name,
+                                   create_aggregate_function_regr<RegrFunctionKind::regr_avgx>);
+    factory.register_function_both(RegrTraits<RegrFunctionKind::regr_avgy>::name,
+                                   create_aggregate_function_regr<RegrFunctionKind::regr_avgy>);
+    factory.register_function_both(RegrTraits<RegrFunctionKind::regr_count>::name,
+                                   create_aggregate_function_regr<RegrFunctionKind::regr_count>);
+    factory.register_function_both(RegrTraits<RegrFunctionKind::regr_slope>::name,
+                                   create_aggregate_function_regr<RegrFunctionKind::regr_slope>);
+    factory.register_function_both(
+            RegrTraits<RegrFunctionKind::regr_intercept>::name,
+            create_aggregate_function_regr<RegrFunctionKind::regr_intercept>);
+    factory.register_function_both(RegrTraits<RegrFunctionKind::regr_sxx>::name,
+                                   create_aggregate_function_regr<RegrFunctionKind::regr_sxx>);
+    factory.register_function_both(RegrTraits<RegrFunctionKind::regr_syy>::name,
+                                   create_aggregate_function_regr<RegrFunctionKind::regr_syy>);
+    factory.register_function_both(RegrTraits<RegrFunctionKind::regr_sxy>::name,
+                                   create_aggregate_function_regr<RegrFunctionKind::regr_sxy>);
+    factory.register_function_both(RegrTraits<RegrFunctionKind::regr_r2>::name,
+                                   create_aggregate_function_regr<RegrFunctionKind::regr_r2>);
+}
+
+} // namespace doris