[SPARK-25797] Views created via 2.1 cannot be read via 2.2+

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.2.0, 2.2.1, 2.2.2, 2.3.0, 2.3.1, 2.3.2
• Fix Version/s: 2.2.3, 2.3.3, 2.4.0
• Component/s: SQL
• Assignee: Chenxiao Mao
• Reporter: Chenxiao Mao
• Created: 22/Oct/18 07:15
• Updated: 29/Oct/18 04:28
• Resolved: 29/Oct/18 04:28

Description

We ran into this issue when we update our Spark from 2.1 to 2.3. Below's a simple example to reproduce the issue.

Create views via Spark 2.1

create view v1 as
select (cast(1 as decimal(18,0)) + cast(1 as decimal(18,0))) c1;

Query views via Spark 2.3

select * from v1;
Error in query: Cannot up cast `c1` from decimal(20,0) to c1#3906: decimal(19,0) as it may truncate

After investigation, we found that this is because when a view is created via Spark 2.1, the expanded text is saved instead of the original text. Unfortunately, the blow expanded text is buggy.

spark-sql> desc extended v1;
c1 decimal(19,0) NULL
Detailed Table Information
Database default
Table v1
Type VIEW
View Text SELECT `gen_attr_0` AS `c1` FROM (SELECT (CAST(CAST(1 AS DECIMAL(18,0)) AS DECIMAL(19,0)) + CAST(CAST(1 AS DECIMAL(18,0)) AS DECIMAL(19,0))) AS `gen_attr_0`) AS gen_subquery_0

We can see that c1 is decimal(19,0), however in the expanded text there is decimal(19,0) + decimal(19,0) which results in decimal(20,0). Since Spark 2.2, decimal(20,0) in query is not allowed to cast to view definition column decimal(19,0). (https://github.com/apache/spark/pull/16561)

I further tested other decimal calculations. Only add/subtract has this issue.

Create views via 2.1:

create view v1 as
select (cast(1 as decimal(18,0)) + cast(1 as decimal(18,0))) c1;
create view v2 as
select (cast(1 as decimal(18,0)) - cast(1 as decimal(18,0))) c1;
create view v3 as
select (cast(1 as decimal(18,0)) * cast(1 as decimal(18,0))) c1;
create view v4 as
select (cast(1 as decimal(18,0)) / cast(1 as decimal(18,0))) c1;
create view v5 as
select (cast(1 as decimal(18,0)) % cast(1 as decimal(18,0))) c1;
create view v6 as
select cast(1 as decimal(18,0)) c1
union
select cast(1 as decimal(19,0)) c1;

Query views via Spark 2.3

select * from v1;
Error in query: Cannot up cast `c1` from decimal(20,0) to c1#3906: decimal(19,0) as it may truncate
select * from v2;
Error in query: Cannot up cast `c1` from decimal(20,0) to c1#3909: decimal(19,0) as it may truncate
select * from v3;
1
select * from v4;
1
select * from v5;
0
select * from v6;
1

Views created via Spark 2.2+ don't have this issue because Spark 2.2+ does not generate expanded text for view (https://issues.apache.org/jira/browse/SPARK-18209).

Issue Links

• relates to: SPARK-18801 Support resolve a nested view
• relates to: SPARK-11012 Canonicalize view definitions
• relates to: HIVE-972 Support views
• relates to: SPARK-18209 More robust view canonicalization without full SQL expansion
• links to: [Github] Pull Request #22846 (seancxmao)
• links to: [Github] Pull Request #22851 (seancxmao)