[IMPALA-2264] Implicit casts to integers from decimals with higher precision sometimes allowed

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: Impala 2.2
• Fix Version/s: Impala 2.3.0, Impala 2.2.10
• Labels: correctness
• Target Version: Impala 2.3.0, Impala 2.2.10
• Assignee: Tim Armstrong
• Reporter: Tim Armstrong
• Created: 28/Aug/15 21:23
• Updated: 08/Apr/16 01:22
• Resolved: 01/Sep/15 00:24

Description

The edge cases are handled incorrectly. E.g. DECIMAL(3,0) has range [-999,999] but can be implicitly cast to TINYINT with range [-128,127]. DECIMAL(2,0) and DECIMAL(4,0) are handled correctly.

[tarmstrong-box.ca.cloudera.com:21000] > create table tinyints(x tinyint);Query: create table tinyints(x tinyint)

Fetched 0 row(s) in 0.04s
[tarmstrong-box.ca.cloudera.com:21000] > insert into tinyints values(CAST(99 as DECIMAL(2,0)));
Query: insert into tinyints values(CAST(99 as DECIMAL(2,0)))
Inserted 1 row(s) in 4.35s
[tarmstrong-box.ca.cloudera.com:21000] > insert into tinyints values(CAST(1000 as DECIMAL(4,0)));
Query: insert into tinyints values(CAST(1000 as DECIMAL(4,0)))
ERROR: AnalysisException: Possible loss of precision for target table 'default.tinyints'.
Expression 'cast(1000 as decimal(4,0))' (type: DECIMAL(4,0)) would need to be cast to TINYINT for column 'x'

[tarmstrong-box.ca.cloudera.com:21000] > insert into tinyints values(CAST(999 as DECIMAL(3,0)));
Query: insert into tinyints values(CAST(999 as DECIMAL(3,0)))
Inserted 1 row(s) in 0.11s
[tarmstrong-box.ca.cloudera.com:21000] > select * from tinyints;
Query: select * from tinyints
+-----+
| x   |
+-----+
| 99  |
| -25 |
+-----+
Fetched 2 row(s) in 0.33s