Gopal V created HIVE-14302:
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Summary: Tez: Optimized Hashtable can support DECIMAL keys of same
precision
Key: HIVE-14302
URL: https://issues.apache.org/jira/browse/HIVE-14302
Project: Hive
Issue Type: Improvement
Components: Tez
Affects Versions: 2.2.0
Reporter: Gopal V
Decimal support in the optimized hashtable was decided on the basis of the fact
that Decimal(10,1) == Decimal(10, 2) when both contain "1.0" and "1.00".
However, the joins now don't have any issues with decimal precision because
they cast to common.
{code}
create temporary table x (a decimal(10,2), b decimal(10,1)) stored as orc;
insert into x values (1.0, 1.0);
> explain logical select count(1) from x, x x1 where x.a = x1.b;
OK
LOGICAL PLAN:
$hdt$_0:$hdt$_0:x
TableScan (TS_0)
alias: x
filterExpr: (a is not null and true) (type: boolean)
Filter Operator (FIL_18)
predicate: (a is not null and true) (type: boolean)
Select Operator (SEL_2)
expressions: a (type: decimal(10,2))
outputColumnNames: _col0
Reduce Output Operator (RS_6)
key expressions: _col0 (type: decimal(11,2))
sort order: +
Map-reduce partition columns: _col0 (type: decimal(11,2))
Join Operator (JOIN_8)
condition map:
Inner Join 0 to 1
keys:
0 _col0 (type: decimal(11,2))
1 _col0 (type: decimal(11,2))
Group By Operator (GBY_11)
aggregations: count(1)
mode: hash
outputColumnNames: _col0
{code}
See cast up to Decimal(11, 2) in the plan, which normalizes both sides of the
join to be able to compare HiveDecimal as-is.
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