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ASF GitHub Bot commented on DRILL-4551: --------------------------------------- Github user jinfengni commented on a diff in the pull request: https://github.com/apache/drill/pull/452#discussion_r57818552 --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/DateTypeFunctions.java --- @@ -40,6 +41,36 @@ public class DateTypeFunctions { + /** + * Function to check if a varchar value can be cast to a date. + * + * At the time of writing this function, several other databases were checked + * for behavior compatibility. There was not a consensus between oracle and + * Sql server about the expected behavior of this function, and Postgres + * lacks it completely. + * + * Sql Server appears to have both a DATEFORMAT and language locale setting + * that can change the values accepted by this function. Oracle appears to + * support several formats, some of which are not mentioned in the Sql + * Server docs. With the lack of standardization, we decided to implement + * this function so that it would only consider date strings that would be + * accepted by the cast function as valid. + */ + @SuppressWarnings("unused") + @FunctionTemplate(name = "isdate", scope = FunctionTemplate.FunctionScope.SIMPLE, nulls=NullHandling.NULL_IF_NULL, --- End diff -- Have you checked isdate() returns null for null input in other system like oracle? I thought it would return either true or false. > Add some missing functions that are generated by Tableau (cot, regex_matches, > split_part, isdate) > ------------------------------------------------------------------------------------------------- > > Key: DRILL-4551 > URL: https://issues.apache.org/jira/browse/DRILL-4551 > Project: Apache Drill > Issue Type: Improvement > Reporter: Jason Altekruse > Assignee: Jason Altekruse > > Several of these functions do not appear to be standard SQL functions, but > they are available in several other popular databases like SQL Server, Oracle > and Postgres. -- This message was sent by Atlassian JIRA (v6.3.4#6332)