[
https://issues.apache.org/jira/browse/HIVE-18434?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16323174#comment-16323174
]
Xuefu Zhang commented on HIVE-18434:
------------------------------------
Thanks for the explanation. While your patch may fix the particular problem,
I'm afraid it might introduce inconsistency in treating string literals for
numbers. My understanding is that Hive treats and implicitly converts number
string literals (such as "3.1415926" as double rather than decimal. When a
decimal (as precise data type) and a double (as imprecise data type) appear in
the same numeric or logical operations, the result data type is double. For
instance:
{code}
hive> explain select 3.14BD + "3.14";
OK
STAGE DEPENDENCIES:
Stage-0 is a root stage
STAGE PLANS:
Stage: Stage-0
Fetch Operator
limit: -1
Processor Tree:
TableScan
alias: _dummy_table
Row Limit Per Split: 1
Statistics: Num rows: 1 Data size: 1 Basic stats: COMPLETE Column
stats: COMPLETE
Select Operator
expressions: 6.28 (type: double)
outputColumnNames: _col0
Statistics: Num rows: 1 Data size: 8 Basic stats: COMPLETE Column
stats: COMPLETE
ListSink
hive> desc dec1;
OK
name string
value decimal(5,2)
hive> explain select * from dec1 where value="3.14";
OK
STAGE DEPENDENCIES:
Stage-0 is a root stage
STAGE PLANS:
Stage: Stage-0
Fetch Operator
limit: -1
Processor Tree:
TableScan
alias: dec1
filterExpr: (value = '3.14') (type: boolean)
Statistics: Num rows: 1 Data size: 0 Basic stats: PARTIAL Column
stats: NONE
Filter Operator
predicate: (value = '3.14') (type: boolean)
Statistics: Num rows: 1 Data size: 0 Basic stats: PARTIAL Column
stats: NONE
Select Operator
expressions: name (type: string), value (type: decimal(5,2))
outputColumnNames: _col0, _col1
Statistics: Num rows: 1 Data size: 0 Basic stats: PARTIAL Column
stats: NONE
ListSink
{code}
I believe that {{ filterExpr: (value = '3.14') (type: boolean)}} will convert
both side to double and than compare internally.
The problem you described seems to be one related to constant optimization.
Specifically, the select op should project {{a}} instead of the following:
{code}
Select Operator
expressions: -1511503446182.5518 (type: decimal(19,6))
{code}
The numeric comparison should be still based on double. We cannot just use
what's is used in the filter condition to rewrite the projection columns.
> Type is not determined correctly for comparison between decimal column and
> string constant
> ------------------------------------------------------------------------------------------
>
> Key: HIVE-18434
> URL: https://issues.apache.org/jira/browse/HIVE-18434
> Project: Hive
> Issue Type: Bug
> Components: Types
> Reporter: Ashutosh Chauhan
> Assignee: Ashutosh Chauhan
> Attachments: HIVE-18434.patch
>
>
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
