BigQuery 视图的神秘之处

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);

然后我将它保存为一个名为 dataset.myview 的视图，并且运行:

SELECT * FROM dataset.myview LIMIT 1000

但这会引发以下错误：

SELECT query which references non constant fields or uses aggregation functions or has one or more of WHERE, OMIT IF, GROUP BY, ORDER BY clauses must have FROM clause.

然而，当我尝试：SELECT * FROM dataset.myview，即没有 LIMIT，它起作用了！！

事实上，当我运行我在底部使用 LIMIT 进行完整查询时，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，当我添加内部 ORDER BY 时，它再次计算良好：

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

如果您对视图中的 select 应用 order by 会怎样？还是您需要随机结果？

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.

我不确定这里的顺序为什么会有所不同。但是，看到没有任何顺序的限制通常很奇怪；这就是为什么我询问订单。一个完整的 SWAG 可能是并行工作人员在内部 select 完成之前完成外部连接和限制，从而导致内部错误；并通过系统应用命令强制在执行内部连接之前具体化记录。

但我真的~~没有线索~

BigQuery 视图的神秘之处

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