[IMPALA-3155] CHAR expression in case statement is implicitly cast to string

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 2.5.0
• Component/s: Frontend
• Labels: ramp-up
• Target Version: Impala 2.6.0
• Assignee: Taras Bobrovytsky
• Reporter: Tim Armstrong
• Created: 08/Mar/16 17:14
• Updated: 07/May/16 02:23
• Resolved: 07/May/16 02:23

Description

Joe Prosser reports this odd behaviour:

[jvp1-3.vpc.cloudera.com:21000] > create table c (v char(1));

Query: create table c (v char(1))

Fetched 0 row(s) in 0.26s



-- This simple cast works for an insert

[jvp1-3.vpc.cloudera.com:21000] > insert into c select cast('a' as char(1));

Query: insert into c select cast('a' as char(1))

Inserted 1 row(s) in 5.20s



-- this one when using a case statement gives a precision error

[jvp1-3.vpc.cloudera.com:21000] > insert into c select case when 5 < 3 then cast('L'  as char(1))  else cast('M'  as char(1)) end as v;

Query: insert into c select case when 5 < 3 then cast('L'  as char(1))  else cast('M'  as char(1)) end as v

ERROR: AnalysisException: Possible loss of precision for target table 'ilimisp01_eciw.c'.

Expression 'CASE WHEN 5 < 3 THEN CAST('L' AS CHAR(1)) ELSE CAST('M' AS CHAR(1)) END' (type: STRING) would need to be cast to CHAR(1) for column 'v'



-- the same thing works with varchar though:

[jvp1-3.vpc.cloudera.com:21000] > create table vc (v varchar(1));

Query: create table vc (v varchar(1))

Fetched 0 row(s) in 0.23s

[jvp1-3.vpc.cloudera.com:21000] > insert into vc select case when 5 < 3 then cast('L'  as varchar(1))  else cast('M'  as varchar(1)) end as v;

Query: insert into vc select case when 5 < 3 then cast('L'  as varchar(1))  else cast('M'  as varchar(1)) end as v

Inserted 1 row(s) in 4.88s