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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
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Daniel John Debrunner commented on DERBY-2917:
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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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