Question

这是我的谜。在控制台上，当我计算这个查询时，它运行得非常好：

SELECT rd.ds_id AS ds_id
FROM (SELECT ds_id, 1 AS dummy FROM bq_000010.table) rd
  INNER JOIN EACH (SELECT 1 AS dummy) cal ON (cal.dummy = rd.dummy);

然后我将其保存为名为dataset.myview的视图，然后运行：

SELECT * FROM dataset.myview LIMIT 1000

但这会引发以下错误：

引用非常量字段或使用聚合的SELECT查询函数或具有WHERE，OMIT IF，GROUP BY，ORDER BY中的一个或多个条款必须有FROM子句。

然而，当我尝试：SELECT * FROM dataset.myview时，即没有LIMIT，它就有效!!

事实上，当我使用底部的LIMIT运行我的完整查询时，它也会引发错误：

SELECT rd.ds_id AS ds_id
FROM (SELECT ds_id, 1 AS dummy FROM bq_000010.table) rd
  INNER JOIN EACH (SELECT 1 AS dummy) cal ON (cal.dummy = rd.dummy) LIMIT 1000;

然而，当我添加一个内部ORDER BY时，它再次计算得很好：

SELECT rd.ds_id AS ds_id
FROM (SELECT ds_id,
             1 AS dummy
      FROM bq_000010.000010_flux_visites_ds
      ORDER BY ds_id) rd
  INNER JOIN EACH (SELECT 1 AS dummy) cal ON (cal.dummy = rd.dummy) LIMIT 1000

Answer 1

如果您在视图上的选择中应用订单会怎样？或者你需要随机结果？

A query with a LIMIT clause may still be non-deterministic if there is no operator in the query that guarantees the ordering of the output result set. This is because BigQuery executes using a large number of parallel workers. The order in which parallel jobs return is not guaranteed.

我不确定为什么这里的订单会产生影响。然而，看到没有任何订单的限制通常很奇怪;这就是我询问订单的原因。一个完整的SWAG可能是并行工作者在内部选择完成之前完成外部连接和限制，从而导致内部错误;并且通过系统应用命令强制在执行内连接连接之前实现记录。

但我真的~~没有CLUE~

关于BigQuery视图的神秘感

1 个答案: