优化count查询速度

lxDb/sql.go

@@ -214,6 +214,95 @@ func SqlQuery(tx *gorm.DB, sql string, list interface{}, q *PaginationQuery, par
 		params = make([]interface{}, 0)
 	}
 
+	// 条件字段
+	if q != nil {
+		where, args := q.BuildRawWhere()
+		if hasWhere(sql) { // 原SQL已有WHERE子句
+			builder.WriteString(where) // 去掉where 前头的and or ..
+		} else { // 原SQL没有WHERE子句
+			if strings.HasPrefix(where, " AND ") {
+				where = strings.Replace(where, " AND ", " WHERE ", 1)
+				builder.WriteString(where)
+			} else if strings.HasPrefix(where, " OR ") {
+				where = strings.Replace(where, " OR ", " WHERE ", 1)
+				builder.WriteString(where)
+			} else {
+				builder.WriteString(where) // "" 或者 " GROUP BY ..."
+			}
+		}
+		if len(args) > 0 {
+			params = append(params, args...)
+		}
+
+		// 半成品 sql 用于查询其他信息
+		var sql2 = builder.String()
+
+		// 记录条数
+		if needDoCount(q) {
+			var total int64
+			//tx = tx.Count(&total)
+			tx.Raw("SELECT COUNT(*) as total FROM ("+sql2+") aaaa", params...).Take(&total)
+			q.Total = int(total)
+			if total == 0 { // 如果查了记录条数并且是0, 就不需要查记录和汇总了
+				return
+			}
+
+			// 获取汇总信息 // TODO: 汇总应该放到查询列表的后面
+			if q.Summary != "" && len(q.SummarySql) == 0 {
+				q.SummarySql = fieldsToSumSql(q.Summary)
+			}
+			if len(q.Summary) != 0 {
+				tx = tx.Offset(-1) // 需要去除offset, 否则结果可能为空, 注意: 设置0不起作用.
+				var summary = make(map[string]interface{})
+				//tx.Order("") // FIXME: 怎么去掉order by, sum是不需要order by的, 影响性能.
+				//tx.Select(q.SummarySql).Take(&summary) // 不适合rawsql?
+
+				tx.Raw("SELECT "+strings.Join(q.SummarySql, ", ")+" FROM ("+sql2+") ssss", params...).Take(&summary)
+
+				// []byte 转 string. 不太合理, 应该返回int或float
+				for k, v := range summary {
+					if bs, ok := v.([]byte); ok {
+						summary[k] = string(bs)
+					}
+				}
+				q.SummaryResult = summary
+			}
+		}
+
+		// 排序处理
+		if q.OrderBy != "" {
+			s := fmt.Sprintf(" ORDER BY %s", lxUtil.FieldToColumn(q.OrderBy)) // TODO: q.OrderBy是字符串,可能多个字段 会有问题吗
+			builder.WriteString(s)
+		}
+
+		// 偏移量处理
+		if q.Limit > 0 {
+			if q.Offset > 0 {
+				offset := (q.Offset - 1) * q.Limit
+				s := fmt.Sprintf(" LIMIT %d, %d", offset, q.Limit)
+				builder.WriteString(s)
+			} else {
+				s := fmt.Sprintf(" LIMIT %d", q.Limit)
+				builder.WriteString(s)
+			}
+		}
+	}
+
+	//tx.Raw(builder.String(), params...).Scan(list) // FIXME: unsupported data type: &[] why?
+	tx.Raw(builder.String(), params...).Find(list) // Find与Scan区别: list传入[]时, 查询为空的情况下, Find返回的是[], 而Scan返回的是nil.
+	// ref: What is the difference between Find and Scan: https://github.com/go-gorm/gorm/issues/4218
+
+	return
+}
+
+func SqlQueryNew(tx *gorm.DB, sql string, list interface{}, q *PaginationQuery, params ...interface{}) (err error) {
+	var builder strings.Builder
+	builder.WriteString(sql)
+
+	if params == nil {
+		params = make([]interface{}, 0)
+	}
+
 	// 条件字段
 	if q != nil {
 		where, args := q.BuildRawWhere()
@@ -417,7 +506,7 @@ func replaceSelectAndRemoveGroupBy(sql string) string {
 	replacedSQL := sql[:selectIndex+6] + " " + newSelectClause + " " + sql[fromIndex:]
 
 	// 去掉 GROUP BY 子句
-	groupByIndex := strings.Index(strings.ToUpper(replacedSQL), "GROUP BY")
+	groupByIndex := strings.LastIndex(strings.ToUpper(replacedSQL), "GROUP BY")
 	if groupByIndex != -1 {
 		c := replacedSQL[groupByIndex+8:]
 		c = strings.TrimSpace(c)