Details
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Sub-task
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Status: Resolved
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Major
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Resolution: Fixed
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Impala 1.4
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None
Description
Consider the following sequence:
[localhost:21000] > describe foo;
Query: describe foo
+------+----------------+---------+
| name | type | comment |
+------+----------------+---------+
| d | decimal(38,38) | |
+------+----------------+---------+
Returned 1 row(s) in 1.00s
[localhost:21000] > insert into foo values(cast(0.1 as Decimal(38,38)));
Query: insert into foo values(cast(0.1 as Decimal(38,38)))
Inserted 1 rows in 0.38s
[localhost:21000] > select * from foo;
Query: select * from foo
+------------------------------------------+
| d |
+------------------------------------------+
| 0.09999999999999998358171037484709838848 |
+------------------------------------------+
Returned 1 row(s) in 0.44s
[localhost:21000] > insert into foo values(cast("0.1" as Decimal(38,38)));
Query: insert into foo values(cast("0.1" as Decimal(38,38)))
Inserted 1 rows in 0.38s
[localhost:21000] > select * from foo;
Query: select * from foo
+------------------------------------------+
| d |
+------------------------------------------+
| 0.09999999999999998358171037484709838848 |
| 0.10000000000000000000000000000000000000 |
+------------------------------------------+
Returned 2 row(s) in 0.44s
Nong told me that in the frontend, we first cast the the number in the query string to a double, and then recast it to decimal. Since the second cast is on Java's encoding of double, we get a very odd result when reading the column value as a Decimal. I'm not sure if it's possible to not do the cast when we're recasting it anyways, but that would be ideal.