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https://issues.apache.org/jira/browse/DRILL-8136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17600062#comment-17600062
]
ASF GitHub Bot commented on DRILL-8136:
---------------------------------------
cgivre commented on PR #2638:
URL: https://github.com/apache/drill/pull/2638#issuecomment-1236342717
@jnturton Thanks for this. IMHO this will be a MAJOR improvement in
usability. I have a question about date conversions. Let's say we have a
query like this:
```sql
SELECT...
FROM ...
WHERE dateField > '2020-01-01'
```
Queries like that will work in MySQL and other RDBMS. In Drill I think they
won't fail, but the results are not what people expect. For cases like this,
would `'2020-01-01'` be automatically cast to a date? Would the same thing
happen in situations like:
```
DATE_DIFF('2020-01-01', '2021-01-01')
```
> Overhaul implict type casting logic
> -----------------------------------
>
> Key: DRILL-8136
> URL: https://issues.apache.org/jira/browse/DRILL-8136
> Project: Apache Drill
> Issue Type: Improvement
> Reporter: Esther Buchwalter
> Assignee: James Turton
> Priority: Minor
>
> The existing implicit casting system is built on simplistic total ordering of
> data types[1] that yields oddities such as TINYINT being regarded as the
> closest numeric type to VARCHAR or DATE the closest type to FLOAT8. This, in
> turn, hurts the range of data types with which SQL functions can be used.
> E.g. `select sqrt('3.1415926')` works in many RDBMSes but not in Drill while,
> confusingly, `select '123' + 456` does work in Drill. In addition the
> limitations of the existing type precedence list mean that it has been
> supplmented with ad hoc secondary casting rules that go in the opposite
> direction.
> This Issue proposes a new, more flexible definition of casting distance based
> on a weighted directed graph built over the Drill data types.
> [1]
> [https://drill.apache.org/docs/supported-data-types/#implicit-casting-precedence-of-data-types]
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