Snowflake 加入性能改进

Question

我需要在包含 1300 多列的 table 之上创建一个视图。新数据将每季度加载到 table（以百万行为单位）。创建视图时，我需要将其他 table 与基础 table 连接起来。我还需要在视图中添加一个最近的行指示符。

CREATE OR REPLACE SECURE VIEW VIEW_NAME AS
SELECT lkp_tbl.col1,base_tbl.col1,base_tbl.col2,base_tbl.col3,........,
base_tbl.col1334, 1 as Is_Latest_Quarter 
FROM base_tbl full outer JOIN lkp_tbl
on base_tbl.CUST_ID = lkp_tbl.CUST_ID 
where snapshot_dt=(select max(snapshot_dt) from base_tbl)


union all


SELECT lkp_tbl.col1,base_tbl.col1,base_tbl.col2,base_tbl.col3,........,
base_tbl.col1334,0 as Is_Latest_Quarter 
FROM base_tbl full outer JOIN lkp_tbl 
on base_tbl.CUST_ID = lkp_tbl.CUST_ID 
where snapshot_dt!=(select max(snapshot_dt) from base_tbl);

创建此视图后，即使我们查询 100 行，查询性能也太慢了。有没有一种方法可以更有效地创建视图。如果不能，我该如何提高性能？

Answer 1

只用一个SELECT语句，用一个CASE语句计算Is_Latest_Quarter

已更新（几乎）实际 SQL

CREATE OR REPLACE SECURE VIEW VIEW_NAME AS
SELECT {list of columns you want to include}
,CASE WHEN snapshot_dt=(select max(snapshot_dt) from base_tbl) THEN 1 
 ELSE 0 END as Is_Latest_Quarter
FROM base_tbl 
full outer JOIN lkp_tbl on base_tbl.CUST_ID = lkp_tbl.CUST_ID

或者，如果 Snowflake 不喜欢该内联子查询，您可以使用类似以下的 CTE：

CREATE OR REPLACE SECURE VIEW VIEW_NAME AS
    WITH MAX_DATE AS (SELECT MAX(Ssnapshot_dt) AS max_snapshot_dt FROM base_tbl),
    SELECT {list of columns you want to include}
    ,CASE WHEN max_date.max_snapshot_dt is not null  THEN 1 
     ELSE 0 END as Is_Latest_Quarter
    FROM base_tbl 
    full outer JOIN lkp_tbl on base_tbl.CUST_ID = lkp_tbl.CUST_ID
    LEFT OUTER JOIN MAX_DATE ON base_tbl.snapshot_dt = max_date.max_snapshot_dt

Snowflake 加入性能改进

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