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Date: Fri, 1 Feb 2008 15:01:12 -0800 (PST)
From: "Daniel John Debrunner (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Commented: (DERBY-2917) Refactor DataTypeDescriptor and
 TypeDescriptor to result in cleaner code.
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    [ https://issues.apache.org/jira/browse/DERBY-2917?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12564968#action_12564968 ] 

Daniel John Debrunner commented on DERBY-2917:
----------------------------------------------

Note on upgrade from older releases:

Objects that are org.apache.derby.catalog.TypeDescriptor can be stored in these two system catalogs:

SYSALIASES - ALIASINFO column as fields with a RoutineAliasInfo (parameter types and return types)
SYSCOLUMNS - COLUMNDATATYPE 
-----------------------------------------------------------------------------------------------------------------------

SYSCOLUMNS.COLUMNDATATYPE is always populated with a TypeDescriptorImpl which is the simple correct form of TypeDescriptor for catalogs.
   SYSCOLUMNSRowFactory has enforced this since the code was contributed. Thus there are no upgrade issues for this catalog.

SYSALIASES - ALIASINFO is populated with the runtime DataTypeDescriptor in releases older than 10.4, thus their on-disk format for a RoutineAliasInfo uses the serialized version that includes duplicate information (see earlier comment). Some upgrade code might be needed for 10.4 to cope with this format.

> Refactor DataTypeDescriptor and TypeDescriptor to result in cleaner code.
> -------------------------------------------------------------------------
>
>                 Key: DERBY-2917
>                 URL: https://issues.apache.org/jira/browse/DERBY-2917
>             Project: Derby
>          Issue Type: Sub-task
>          Components: Services, SQL
>            Reporter: Daniel John Debrunner
>            Assignee: Daniel John Debrunner
>
> TypeDescriptor ideally represents a catalog type (column in a table, parameter in a procedure etc.)
> DataTypeDescriptor represents a runtime type
> Currently DataTypeDescriptor  extends (implements) TypeDescriptor , but the relationship would be cleaner if DataTypeDescriptor  had a TypeDescriptor (but was not a TypeDescriptor).
> One can at the moment obtain a TypeDescriptor from a DataTypeDescriptor  using DataTypeDescriptor.getCatalogType() but most code just treats DataTypeDescriptor   as a TypeDescriptor. This has lead to a couple of issues:
> 1) When a routine's parameter/return type is written out a DataTypeDescriptor is written to disk. This results in type information being repeated in the serialized form, thus increasing the on-disk size of a Derby database.
> 2) Collation derivation is runtime only (all persistent types by definition have implicit type) but the derivation is on the catalog Typedescriptor interface.

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