分库分表：结果集处理——聚合函数（不含 Group By 子句)

.CHANGELOG.md

@@ -20,6 +20,7 @@
 - [eorm: 分库分表: Merger分页实现](https://github.com/ecodeclub/eorm/pull/175)
 - [eorm: BasicTypeValue重命名](https://github.com/ecodeclub/eorm/pull/177)
 - [eorm: 分库分表: hash、shadow_hash算法不符合预期](https://github.com/ecodeclub/eorm/pull/174)
+- [eorm: 分库分表: 结果集处理--聚合函数(不含GroupBy子句)](https://github.com/ecodeclub/eorm/pull/187)
 - [eorm: 修复单条查询时连接泄露问题](https://github.com/ecodeclub/eorm/pull/188)
 
 ## v0.0.1:

internal/merger/aggregatemerger/aggregator/avg.go

@@ -0,0 +1,234 @@
+// Copyright 2021 ecodeclub
+//
+// Licensed 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.
+
+package aggregator
+
+import (
+	"reflect"
+
+	"github.com/ecodeclub/eorm/internal/merger/internal/errs"
+)
+
+// AVG 用于求平均值，通过sum/count求得。
+// AVG 我们并不能预期在不同的数据库上，精度会不会损失，自己损失的话会有多少的损失。这很大程度上跟数据库类型，数据库驱动实现都有关
+type AVG struct {
+	sumColumnInfo   ColumnInfo
+	countColumnInfo ColumnInfo
+	alias           string
+}
+
+// NewAVG sumInfo是sum的信息，countInfo是count的信息，这两个顺序不能颠倒。
+func NewAVG(sumInfo ColumnInfo, countInfo ColumnInfo, alias string) *AVG {
+	return &AVG{
+		sumColumnInfo:   sumInfo,
+		countColumnInfo: countInfo,
+		alias:           alias,
+	}
+}
+
+func (a *AVG) Aggregate(cols [][]any) (any, error) {
+	sumIndex := a.sumColumnInfo.Index
+	countIndex := a.countColumnInfo.Index
+	if sumIndex >= len(cols[0]) || sumIndex < 0 || countIndex >= len(cols[0]) || countIndex < 0 {
+		return nil, errs.ErrMergerInvalidAggregateColumnIndex
+	}
+	ok, avgFunc := a.findSumAndCountReflectKindBy(cols[0][sumIndex], cols[0][countIndex])
+	if !ok {
+		return nil, errs.ErrMergerAggregateFuncNotFound
+	}
+	return avgFunc(cols, sumIndex, countIndex)
+
+}
+
+func (a *AVG) findSumAndCountReflectKindBy(sum, count any) (bool, func([][]any, int, int) (any, error)) {
+	sumKind := reflect.TypeOf(sum).Kind()
+	countKind := reflect.TypeOf(count).Kind()
+	val, ok := avgAggregateFuncMapping[[2]reflect.Kind{sumKind, countKind}]
+	return ok, val
+}
+
+func (a *AVG) ColumnName() string {
+	return a.alias
+}
+
+// avgAggregator cols就是上面Aggregate的入参cols可以参Aggregate的描述
+func avgAggregator[S AggregateElement, C AggregateElement](cols [][]any, sumIndex int, countIndex int) (any, error) {
+	var sum S
+	var count C
+	for _, col := range cols {
+		sum += col[sumIndex].(S)
+		count += col[countIndex].(C)
+	}
+	val := float64(sum) / float64(count)
+	return val, nil
+
+}
+
+var avgAggregateFuncMapping = map[[2]reflect.Kind]func([][]any, int, int) (any, error){
+	[2]reflect.Kind{reflect.Int, reflect.Int}:     avgAggregator[int, int],
+	[2]reflect.Kind{reflect.Int, reflect.Int8}:    avgAggregator[int, int8],
+	[2]reflect.Kind{reflect.Int, reflect.Int16}:   avgAggregator[int, int16],
+	[2]reflect.Kind{reflect.Int, reflect.Int32}:   avgAggregator[int, int32],
+	[2]reflect.Kind{reflect.Int, reflect.Int64}:   avgAggregator[int, int64],
+	[2]reflect.Kind{reflect.Int, reflect.Uint}:    avgAggregator[int, uint],
+	[2]reflect.Kind{reflect.Int, reflect.Uint8}:   avgAggregator[int, uint8],
+	[2]reflect.Kind{reflect.Int, reflect.Uint16}:  avgAggregator[int, uint16],
+	[2]reflect.Kind{reflect.Int, reflect.Uint32}:  avgAggregator[int, uint32],
+	[2]reflect.Kind{reflect.Int, reflect.Uint64}:  avgAggregator[int, uint64],
+	[2]reflect.Kind{reflect.Int, reflect.Float32}: avgAggregator[int, float32],
+	[2]reflect.Kind{reflect.Int, reflect.Float64}: avgAggregator[int, float64],
+
+	[2]reflect.Kind{reflect.Int8, reflect.Int}:     avgAggregator[int8, int],
+	[2]reflect.Kind{reflect.Int8, reflect.Int8}:    avgAggregator[int8, int8],
+	[2]reflect.Kind{reflect.Int8, reflect.Int16}:   avgAggregator[int8, int16],
+	[2]reflect.Kind{reflect.Int8, reflect.Int32}:   avgAggregator[int8, int32],
+	[2]reflect.Kind{reflect.Int8, reflect.Int64}:   avgAggregator[int8, int64],
+	[2]reflect.Kind{reflect.Int8, reflect.Uint}:    avgAggregator[int8, uint],
+	[2]reflect.Kind{reflect.Int8, reflect.Uint8}:   avgAggregator[int8, uint8],
+	[2]reflect.Kind{reflect.Int8, reflect.Uint16}:  avgAggregator[int8, uint16],
+	[2]reflect.Kind{reflect.Int8, reflect.Uint32}:  avgAggregator[int8, uint32],
+	[2]reflect.Kind{reflect.Int8, reflect.Uint64}:  avgAggregator[int8, uint64],
+	[2]reflect.Kind{reflect.Int8, reflect.Float32}: avgAggregator[int8, float32],
+	[2]reflect.Kind{reflect.Int8, reflect.Float64}: avgAggregator[int8, float64],
+
+	[2]reflect.Kind{reflect.Int16, reflect.Int}:     avgAggregator[int16, int],
+	[2]reflect.Kind{reflect.Int16, reflect.Int8}:    avgAggregator[int16, int8],
+	[2]reflect.Kind{reflect.Int16, reflect.Int16}:   avgAggregator[int16, int16],
+	[2]reflect.Kind{reflect.Int16, reflect.Int32}:   avgAggregator[int16, int32],
+	[2]reflect.Kind{reflect.Int16, reflect.Int64}:   avgAggregator[int16, int64],
+	[2]reflect.Kind{reflect.Int16, reflect.Uint}:    avgAggregator[int16, uint],
+	[2]reflect.Kind{reflect.Int16, reflect.Uint8}:   avgAggregator[int16, uint8],
+	[2]reflect.Kind{reflect.Int16, reflect.Uint16}:  avgAggregator[int16, uint16],
+	[2]reflect.Kind{reflect.Int16, reflect.Uint32}:  avgAggregator[int16, uint32],
+	[2]reflect.Kind{reflect.Int16, reflect.Uint64}:  avgAggregator[int16, uint64],
+	[2]reflect.Kind{reflect.Int16, reflect.Float32}: avgAggregator[int16, float32],
+	[2]reflect.Kind{reflect.Int16, reflect.Float64}: avgAggregator[int16, float64],
+
+	[2]reflect.Kind{reflect.Int32, reflect.Int}:     avgAggregator[int16, int],
+	[2]reflect.Kind{reflect.Int32, reflect.Int8}:    avgAggregator[int16, int8],
+	[2]reflect.Kind{reflect.Int32, reflect.Int16}:   avgAggregator[int16, int16],
+	[2]reflect.Kind{reflect.Int32, reflect.Int32}:   avgAggregator[int16, int32],
+	[2]reflect.Kind{reflect.Int32, reflect.Int64}:   avgAggregator[int16, int64],
+	[2]reflect.Kind{reflect.Int32, reflect.Uint}:    avgAggregator[int16, uint],
+	[2]reflect.Kind{reflect.Int32, reflect.Uint8}:   avgAggregator[int16, uint8],
+	[2]reflect.Kind{reflect.Int32, reflect.Uint16}:  avgAggregator[int16, uint16],
+	[2]reflect.Kind{reflect.Int32, reflect.Uint32}:  avgAggregator[int16, uint32],
+	[2]reflect.Kind{reflect.Int32, reflect.Uint64}:  avgAggregator[int16, uint64],
+	[2]reflect.Kind{reflect.Int32, reflect.Float32}: avgAggregator[int16, float32],
+	[2]reflect.Kind{reflect.Int32, reflect.Float64}: avgAggregator[int16, float64],
+
+	[2]reflect.Kind{reflect.Int64, reflect.Int}:     avgAggregator[int64, int],
+	[2]reflect.Kind{reflect.Int64, reflect.Int8}:    avgAggregator[int64, int8],
+	[2]reflect.Kind{reflect.Int64, reflect.Int16}:   avgAggregator[int64, int16],
+	[2]reflect.Kind{reflect.Int64, reflect.Int32}:   avgAggregator[int64, int32],
+	[2]reflect.Kind{reflect.Int64, reflect.Int64}:   avgAggregator[int64, int64],
+	[2]reflect.Kind{reflect.Int64, reflect.Uint}:    avgAggregator[int64, uint],
+	[2]reflect.Kind{reflect.Int64, reflect.Uint8}:   avgAggregator[int64, uint8],
+	[2]reflect.Kind{reflect.Int64, reflect.Uint16}:  avgAggregator[int64, uint16],
+	[2]reflect.Kind{reflect.Int64, reflect.Uint32}:  avgAggregator[int64, uint32],
+	[2]reflect.Kind{reflect.Int64, reflect.Uint64}:  avgAggregator[int64, uint64],
+	[2]reflect.Kind{reflect.Int64, reflect.Float32}: avgAggregator[int64, float32],
+	[2]reflect.Kind{reflect.Int64, reflect.Float64}: avgAggregator[int64, float64],
+
+	[2]reflect.Kind{reflect.Uint, reflect.Int}:     avgAggregator[uint, int],
+	[2]reflect.Kind{reflect.Uint, reflect.Int8}:    avgAggregator[uint, int8],
+	[2]reflect.Kind{reflect.Uint, reflect.Int16}:   avgAggregator[uint, int16],
+	[2]reflect.Kind{reflect.Uint, reflect.Int32}:   avgAggregator[uint, int32],
+	[2]reflect.Kind{reflect.Uint, reflect.Int64}:   avgAggregator[uint, int64],
+	[2]reflect.Kind{reflect.Uint, reflect.Uint}:    avgAggregator[uint, uint],
+	[2]reflect.Kind{reflect.Uint, reflect.Uint8}:   avgAggregator[uint, uint8],
+	[2]reflect.Kind{reflect.Uint, reflect.Uint16}:  avgAggregator[uint, uint16],
+	[2]reflect.Kind{reflect.Uint, reflect.Uint32}:  avgAggregator[uint, uint32],
+	[2]reflect.Kind{reflect.Uint, reflect.Uint64}:  avgAggregator[uint, uint64],
+	[2]reflect.Kind{reflect.Uint, reflect.Float32}: avgAggregator[uint, float32],
+	[2]reflect.Kind{reflect.Uint, reflect.Float64}: avgAggregator[uint, float64],
+
+	[2]reflect.Kind{reflect.Uint8, reflect.Int}:     avgAggregator[uint8, int],
+	[2]reflect.Kind{reflect.Uint8, reflect.Int8}:    avgAggregator[uint8, int8],
+	[2]reflect.Kind{reflect.Uint8, reflect.Int16}:   avgAggregator[uint8, int16],
+	[2]reflect.Kind{reflect.Uint8, reflect.Int32}:   avgAggregator[uint8, int32],
+	[2]reflect.Kind{reflect.Uint8, reflect.Int64}:   avgAggregator[uint8, int64],
+	[2]reflect.Kind{reflect.Uint8, reflect.Uint}:    avgAggregator[uint8, uint],
+	[2]reflect.Kind{reflect.Uint8, reflect.Uint8}:   avgAggregator[uint8, uint8],
+	[2]reflect.Kind{reflect.Uint8, reflect.Uint16}:  avgAggregator[uint8, uint16],
+	[2]reflect.Kind{reflect.Uint8, reflect.Uint32}:  avgAggregator[uint8, uint32],
+	[2]reflect.Kind{reflect.Uint8, reflect.Uint64}:  avgAggregator[uint8, uint64],
+	[2]reflect.Kind{reflect.Uint8, reflect.Float32}: avgAggregator[uint8, float32],
+	[2]reflect.Kind{reflect.Uint8, reflect.Float64}: avgAggregator[uint8, float64],
+
+	[2]reflect.Kind{reflect.Uint16, reflect.Int}:     avgAggregator[uint16, int],
+	[2]reflect.Kind{reflect.Uint16, reflect.Int8}:    avgAggregator[uint16, int8],
+	[2]reflect.Kind{reflect.Uint16, reflect.Int16}:   avgAggregator[uint16, int16],
+	[2]reflect.Kind{reflect.Uint16, reflect.Int32}:   avgAggregator[uint16, int32],
+	[2]reflect.Kind{reflect.Uint16, reflect.Int64}:   avgAggregator[uint16, int64],
+	[2]reflect.Kind{reflect.Uint16, reflect.Uint}:    avgAggregator[uint16, uint],
+	[2]reflect.Kind{reflect.Uint16, reflect.Uint8}:   avgAggregator[uint16, uint8],
+	[2]reflect.Kind{reflect.Uint16, reflect.Uint16}:  avgAggregator[uint16, uint16],
+	[2]reflect.Kind{reflect.Uint16, reflect.Uint32}:  avgAggregator[uint16, uint32],
+	[2]reflect.Kind{reflect.Uint16, reflect.Uint64}:  avgAggregator[uint16, uint64],
+	[2]reflect.Kind{reflect.Uint16, reflect.Float32}: avgAggregator[uint16, float32],
+	[2]reflect.Kind{reflect.Uint16, reflect.Float64}: avgAggregator[uint16, float64],
+
+	[2]reflect.Kind{reflect.Uint32, reflect.Int}:     avgAggregator[uint32, int],
+	[2]reflect.Kind{reflect.Uint32, reflect.Int8}:    avgAggregator[uint32, int8],
+	[2]reflect.Kind{reflect.Uint32, reflect.Int16}:   avgAggregator[uint32, int16],
+	[2]reflect.Kind{reflect.Uint32, reflect.Int32}:   avgAggregator[uint32, int32],
+	[2]reflect.Kind{reflect.Uint32, reflect.Int64}:   avgAggregator[uint32, int64],
+	[2]reflect.Kind{reflect.Uint32, reflect.Uint}:    avgAggregator[uint32, uint],
+	[2]reflect.Kind{reflect.Uint32, reflect.Uint8}:   avgAggregator[uint32, uint8],
+	[2]reflect.Kind{reflect.Uint32, reflect.Uint16}:  avgAggregator[uint32, uint16],
+	[2]reflect.Kind{reflect.Uint32, reflect.Uint32}:  avgAggregator[uint32, uint32],
+	[2]reflect.Kind{reflect.Uint32, reflect.Uint64}:  avgAggregator[uint32, uint64],
+	[2]reflect.Kind{reflect.Uint32, reflect.Float32}: avgAggregator[uint32, float32],
+	[2]reflect.Kind{reflect.Uint32, reflect.Float64}: avgAggregator[uint32, float64],
+
+	[2]reflect.Kind{reflect.Uint64, reflect.Int}:     avgAggregator[uint64, int],
+	[2]reflect.Kind{reflect.Uint64, reflect.Int8}:    avgAggregator[uint64, int8],
+	[2]reflect.Kind{reflect.Uint64, reflect.Int16}:   avgAggregator[uint64, int16],
+	[2]reflect.Kind{reflect.Uint64, reflect.Int32}:   avgAggregator[uint64, int32],
+	[2]reflect.Kind{reflect.Uint64, reflect.Int64}:   avgAggregator[uint64, int64],
+	[2]reflect.Kind{reflect.Uint64, reflect.Uint}:    avgAggregator[uint64, uint],
+	[2]reflect.Kind{reflect.Uint64, reflect.Uint8}:   avgAggregator[uint64, uint8],
+	[2]reflect.Kind{reflect.Uint64, reflect.Uint16}:  avgAggregator[uint64, uint16],
+	[2]reflect.Kind{reflect.Uint64, reflect.Uint32}:  avgAggregator[uint64, uint32],
+	[2]reflect.Kind{reflect.Uint64, reflect.Uint64}:  avgAggregator[uint64, uint64],
+	[2]reflect.Kind{reflect.Uint64, reflect.Float32}: avgAggregator[uint64, float32],
+	[2]reflect.Kind{reflect.Uint64, reflect.Float64}: avgAggregator[uint64, float64],
+
+	[2]reflect.Kind{reflect.Float32, reflect.Int}:     avgAggregator[float32, int],
+	[2]reflect.Kind{reflect.Float32, reflect.Int8}:    avgAggregator[float32, int8],
+	[2]reflect.Kind{reflect.Float32, reflect.Int16}:   avgAggregator[float32, int16],
+	[2]reflect.Kind{reflect.Float32, reflect.Int32}:   avgAggregator[float32, int32],
+	[2]reflect.Kind{reflect.Float32, reflect.Int64}:   avgAggregator[float32, int64],
+	[2]reflect.Kind{reflect.Float32, reflect.Uint}:    avgAggregator[float32, uint],
+	[2]reflect.Kind{reflect.Float32, reflect.Uint8}:   avgAggregator[float32, uint8],
+	[2]reflect.Kind{reflect.Float32, reflect.Uint16}:  avgAggregator[float32, uint16],
+	[2]reflect.Kind{reflect.Float32, reflect.Uint32}:  avgAggregator[float32, uint32],
+	[2]reflect.Kind{reflect.Float32, reflect.Uint64}:  avgAggregator[float32, uint64],
+	[2]reflect.Kind{reflect.Float32, reflect.Float32}: avgAggregator[float32, float32],
+	[2]reflect.Kind{reflect.Float32, reflect.Float64}: avgAggregator[float32, float64],
+
+	[2]reflect.Kind{reflect.Float64, reflect.Int}:     avgAggregator[float64, int],
+	[2]reflect.Kind{reflect.Float64, reflect.Int8}:    avgAggregator[float64, int8],
+	[2]reflect.Kind{reflect.Float64, reflect.Int16}:   avgAggregator[float64, int16],
+	[2]reflect.Kind{reflect.Float64, reflect.Int32}:   avgAggregator[float64, int32],
+	[2]reflect.Kind{reflect.Float64, reflect.Int64}:   avgAggregator[float64, int64],
+	[2]reflect.Kind{reflect.Float64, reflect.Uint}:    avgAggregator[float64, uint],
+	[2]reflect.Kind{reflect.Float64, reflect.Uint8}:   avgAggregator[float64, uint8],
+	[2]reflect.Kind{reflect.Float64, reflect.Uint16}:  avgAggregator[float64, uint16],
+	[2]reflect.Kind{reflect.Float64, reflect.Uint32}:  avgAggregator[float64, uint32],
+	[2]reflect.Kind{reflect.Float64, reflect.Uint64}:  avgAggregator[float64, uint64],
+	[2]reflect.Kind{reflect.Float64, reflect.Float32}: avgAggregator[float64, float32],
+	[2]reflect.Kind{reflect.Float64, reflect.Float64}: avgAggregator[float64, float64],
+}

internal/merger/aggregatemerger/aggregator/avg_test.go

@@ -0,0 +1,96 @@
+// Copyright 2021 ecodeclub
+//
+// Licensed 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.
+
+package aggregator
+
+import (
+	"testing"
+
+	"github.com/ecodeclub/eorm/internal/merger/internal/errs"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAvg_Aggregate(t *testing.T) {
+	testcases := []struct {
+		name    string
+		input   [][]any
+		index   []int
+		wantVal any
+		wantErr error
+	}{
+		{
+			name: "avg正常合并",
+			input: [][]any{
+				{
+					int64(10),
+					int64(2),
+				},
+				{
+					int64(20),
+					int64(2),
+				},
+				{
+					int64(30),
+					int64(2),
+				},
+			},
+			index:   []int{0, 1},
+			wantVal: float64(10),
+		},
+		{
+			name: "传入的参数非AggregateElement类型",
+			input: [][]any{
+				{
+					"1",
+					"2",
+				},
+				{
+					"3",
+					"4",
+				},
+			},
+			index:   []int{0, 1},
+			wantErr: errs.ErrMergerAggregateFuncNotFound,
+		},
+		{
+			name: "columnInfo的index不合法",
+			input: [][]any{
+				{
+					int64(10),
+					int64(2),
+				},
+				{
+					int64(20),
+					int64(2),
+				},
+			},
+			index:   []int{0, 10},
+			wantErr: errs.ErrMergerInvalidAggregateColumnIndex,
+		},
+	}
+	for _, tc := range testcases {
+		t.Run(tc.name, func(t *testing.T) {
+			avg := NewAVG(NewColInfo(tc.index[0], "SUM(grade)"), NewColInfo(tc.index[1], "COUNT(grade)"), "AVG(grade)")
+			val, err := avg.Aggregate(tc.input)
+			assert.Equal(t, tc.wantErr, err)
+			if err != nil {
+				return
+			}
+			assert.Equal(t, tc.wantVal, val)
+			assert.Equal(t, "AVG(grade)", avg.ColumnName())
+		})
+	}
+
+}