[jira] [Resolved] (SQOOP-1987) Sqoop2: Add a NullMatcher

["Qian Xu (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SQOOP-1987?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Qian Xu resolved SQOOP-1987.
----------------------------
    Resolution: Invalid

The MatcherFactory will create suitable Matcher instance, no need to add extra complexity.

> Sqoop2: Add a NullMatcher
> -------------------------
>
>                 Key: SQOOP-1987
>                 URL: https://issues.apache.org/jira/browse/SQOOP-1987
>             Project: Sqoop
>          Issue Type: Sub-task
>    Affects Versions: 1.99.5
>            Reporter: Qian Xu
>            Assignee: Qian Xu
>            Priority: Minor
>             Fix For: 2.0.0
>
>
> The {{MatcherFactory}} will create a suitable matcher according to toSchema and fromSchema conditions. 
> If {{NameMatcher}} is chosen, it means FROM and TO schema should not be empty, so the following code is not necessary. Thanks [~jerrychenhf] for pointing it out.
> {code}
>   public Object[] getMatchingData(Object[] fields) {
>     if (getToSchema().isEmpty()) {
>       // No destination schema found. No need to convert anything.
>       return fields;
>     }
> {code}
> If {{LocationMatcher}} is chosen, TO schema can be empty. In code there is a rule 0. If TO schema is empty, it will not convert anything. 
> {code}
>   public Object[] getMatchingData(Object[] fields) {
>     if (getToSchema().isEmpty()) {
>       // No destination schema found. No need to convert anything.
>       return fields;
>     }
> {code}
> I'm thinking we can create a third matcher {{NullMatcher}}, which simply return input fields as result. This is a tiny optimization thing. 
> Second, it'd be better to have precondition check in constructor of both matcher classes. So that we know better that when the matcher should be used. And related test cases should be updated, if precondition check is added.



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