springboot-mybatis plus工程统计消费余额的正确方式

统计已经消费的金额，因为数据库的已经消费的条数很多，做统计信息如果全部拉入内存计算，会出现问题，造成请求的接口很慢。
如下图所示的做法：

		override fun getConsumeAmountByTenantId(tenantId: Long): BigDecimal=this.list(
			QueryWrapper().allEq(mapOf("tenant_id" to tenantId, "transaction_type" to TransactionType.ORDER_DEDUCTION))
		).sumOf { it.amount!! }

通过sql进行统计，这样请求会相对快一些

	
	override fun getConsumeAmountByTenantId(tenantId: Long): BigDecimal{
		val queryWrapper: QueryWrapper = QueryWrapper()
		queryWrapper.select("sum(amount) as sum_amount ")
		queryWrapper.allEq(mapOf("tenant_id" to tenantId, "transaction_type" to TransactionType.ORDER_DEDUCTION))
		val sumAmountMap=this.getMap(queryWrapper)?: return BigDecimal.ZERO
		return sumAmountMap["sum_amount"].toString().toBigDecimal()
	}

执行的sql为

SELECT sum(amount) as sum_amount FROM sub_account_record WHERe deleted=0 AND (tenant_id = 1436952636891992064 AND transaction_type = 'EXPIRED_DEDUCTION')