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From jaltekruse <...@git.apache.org>
Subject [GitHub] drill pull request: DRILL-4551: Implement new functions (cot, rege...
Date Wed, 30 Mar 2016 18:50:54 GMT
Github user jaltekruse commented on a diff in the pull request:

    https://github.com/apache/drill/pull/452#discussion_r57942687
  
    --- 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 --
    
    I couldn't find a definite answer on that in the oracle docs, and I didn't have an oracle
install to verify on. This Sql Server page is clear that they do return 0 on null and I assume
oracle is the same, will update the patch. https://msdn.microsoft.com/en-us/library/ms187347.aspx


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