[jira] [Commented] (IGNITE-3698) ODBC: Support LEN(string) function.

["Vladimir Ozerov (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IGNITE-3698?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15430862#comment-15430862 ] 

Vladimir Ozerov commented on IGNITE-3698:
-----------------------------------------

On hold for now, as we probably will not need that once IGNITE-3716 and IGNITE-3627 are ready.

> ODBC: Support LEN(string) function.
> -----------------------------------
>
>                 Key: IGNITE-3698
>                 URL: https://issues.apache.org/jira/browse/IGNITE-3698
>             Project: Ignite
>          Issue Type: Task
>          Components: odbc, SQL
>    Affects Versions: 1.7
>            Reporter: Vladimir Ozerov
>            Assignee: Vladimir Ozerov
>            Priority: Critical
>             Fix For: 1.8
>
>
> *Problem*
> ODBC has standard function LEN(string). We do not support it at the moment because our H2 engine doesn't have this function. Instead, it has LENGTH function [1].
> We need to support LEN as well.
> *Solution*
> It is necessary to investigate how we can add "LEN" support. Most probably we should implement custom H2 function [2] inside "core" module. It can be placed in the package {{org.apache.ignite.internal.processors.query.h2.ext.func}} in the module "ignite-indexing".
> After that we should register it's alias inside the database, so that is LEN is correctly routed to that function.
> There is a chance that we can skip implementation of the new function and directly route LEN alias to built-in LENGTH function. This is the most preferred solution (if achievable). See {{org.h2.expression.Function}} class in H2 JAR. It shows an example on how funcs are registered and mapped to SQL literals. E.g., this is how {{LENGTH}} is mapped:
> {code}
> addFunction("LENGTH", LENGTH, 1, Value.LONG);
> {code}
> Something semantically similar can be found in {{GridSqlFunction}} and {{GridSqlFunctionType}} classes in Ignite. 
> Please also make sure that proper tests are added. 
> [1] http://www.h2database.com/html/functions.html#length
> [2] http://www.h2database.com/html/features.html#user_defined_functions



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