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https://issues.apache.org/jira/browse/DRILL-8136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17599848#comment-17599848
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ASF GitHub Bot commented on DRILL-8136:
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jnturton opened a new pull request, #2638:
URL: https://github.com/apache/drill/pull/2638
# [DRILL-8136](https://issues.apache.org/jira/browse/DRILL-8136): Overhaul
implict type casting logic
## Description
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 PR introduces a new, more flexible definition of casting distance based
on a weighted directed graph built over the Drill data types.
## Documentation
Update [the description of implcit casting
precedence](https://drill.apache.org/docs/supported-data-types/#implicit-casting-precedence-of-data-types).
## Testing
Existing implcit cast unit tests plus new additions.
> 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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