[
https://issues.apache.org/jira/browse/CALCITE-2673?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16687375#comment-16687375
]
Julian Hyde commented on CALCITE-2673:
--------------------------------------
It makes sense that {{SqlDialect.supportsFunction}} is for built-in functions
only. User-defined functions and procedures like in schemas, so should be read
by {{JdbcSchema}}. And {{JdbcSchema}} has access to a connection in order to
read them, whereas {{SqlDialect}} does not.
Comments:
* Some of the functions are not standard or not scalar functions, so should not
be on the list: SECOND, YEAR, VALUES, MINUS, ANY_VALUE.
* It's misleading to have a set called DEFAULT_OPERATORS_LIST
* Please clarify in the javadoc for {{SqlDialect.supportsFunction}} that it
only applies to built-in scalar functions and operators, and that UDFs come
from JdbcSchema.
Jethro's case was because different versions of Jethro might have different
sets of built-in functions. Therefore it is appropriate to have multiple
instances of {{JethroDataSqlDialect}}, each with a different set of function.
However, the implementation had some hacks that I don't want to repeat.
> Default implementation of SqlDialect should not support pushing all functions
> -----------------------------------------------------------------------------
>
> Key: CALCITE-2673
> URL: https://issues.apache.org/jira/browse/CALCITE-2673
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
> Priority: Major
> Fix For: 1.18.0
>
>
> SqlDialect contains a 'supportsFunction' that can be used by rules to know
> whether a certain function is supported in the given dialect, e.g., to choose
> whether to push a Filter expression to JDBC, etc.
> The default implementation of 'supportsFunction' always returns true.
> I believe a better idea would be to support in the default implementation for
> the method the most common SQL functions. Then each dialect can override that
> behavior and expand/limit the supported functions, e.g., JethroDataDialect
> already does that.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
