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From "Eric Jain (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-571) Virtual Table Mapping for no argument Diagnostic tables
Date Thu, 27 Oct 2005 12:59:56 GMT
    [ http://issues.apache.org/jira/browse/DERBY-571?page=comments#action_12356073 ] 

Eric Jain commented on DERBY-571:
---------------------------------

If such virtual tables could be used to integrate Lucene search results with data in relational
tables (e.g. for summaries and sorting), that would be a killer feature for Derby!

> Virtual Table Mapping for no argument Diagnostic tables
> -------------------------------------------------------
>
>          Key: DERBY-571
>          URL: http://issues.apache.org/jira/browse/DERBY-571
>      Project: Derby
>         Type: Improvement
>   Components: SQL
>     Reporter: Daniel John Debrunner
>     Assignee: Daniel John Debrunner
>     Priority: Minor
>      Fix For: 10.2.0.0

>
> Currently four no-argument diagnostic tables exist that provide information about the
running state of Derby, or its error messages.
> These tables are invoked using an awkward, non-standard syntax. As an example:
> SELECT * FROM NEW org.apache.derby.diag.LockTable() as LOCK_TABLE
> The improvement will provide an internal mapping from a regular table name in the SYSCS_DIAG
schema
> to the runtime virtual table code. Thus the above example would be replaced by:
> SELECT * FROM SYSCS_DIAG.LOCK_TABLE
> These diagnostic table expressions are regular table expressions (as is the NEW VTI construct)
and
> can be used wherever a normal table can.
> Any DDL, INSERT/UPDATE/DELETE, compression procedure etc. that references a diagnostic
table
> will result in an exception.
> The old style syntax will remain in place for 10.2, but become deprecated.
> The tables to be implemented in this change are:
> SYSCS_DIAG.LOCK_TABLE   replaces org.apache.derby.diag.LockTable
> SYSCS_DIAG.STATEMENT_CACHE    replaces org.apache.derby.diag.StatementCache
> SYSCS_DIAG.TRANSACTION_TABLE    replaces org.apache.derby.diag.TransactionTable
> SYSCS_DIAG.ERROR_MESSAGES    replaces org.apache.derby.diag.ErrorMessages
> Adding such a table will be table driven, thus easy for others to provide additional
diagnostics.
> Information about these diagnostic tables will not appear in the system catalogs or JDBC
DatabaseMetaData.
> The ResultSetMetaData for the any query involving a diagnostic table will be valid.
> This is a first step in a progression towards supporing a fully application/user defined
virtual table.
> These steps are not part of this jira issue, but added for information purposes.
> - second step - supporting diagnostic tables with parameters, e.g.
>   SELECT * FROM SYSCS_DIAG.SPACE_TABLE('sales', 'orders');
> - third step - providing a create virtual table statement (most databases support
>    some form of virtual table, or wrappers). The DDL would be non-standard but the
>    data access would be standard. [need to check table functions in part 13 of SQL standard]
>    E.g. syntax yet to be defined, but to give the general idea
>       CREATE VIRTUAL TABLE (TICKER VARCHAR(10), START TIMESTAMP, END TIMESTAMP)
>            LANGUAGE JAVA
>            PARAMETER STYLE JAVA
>            EXTERNAL NAME 'com.acme.stocks.historyFromYahooFinance';

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