[DERBY-1107] For existing databases JDBC metadata queries do not get updated properly between maintenance versions.

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 10.0.2.0, 10.0.2.1, 10.1.1.0, 10.1.2.1, 10.1.3.1, 10.2.1.6
• Fix Version/s: 10.5.1.1
• Component/s: JDBC
• Issue & fix info: High Value Fix
• Assignee: Katherine Marsden
• Reporter: Katherine Marsden
• Created: 14/Mar/06 06:48
• Updated: 02/May/13 02:29
• Resolved: 10/Nov/08 17:20

Description

The JDBC DatabaseMetaData queries are stored as stored prepared statements in the database. If a bug is fixed for any of the metadata calls it can require that these queries be changed. Currently existing databases will not get updated properly if a bug is fixed. Ideally the metadata queries should match the derby version that is running. That way we avoid situations where the query is not compatible with the Derby version running.

To confirm I :
1) created a database with 10.1.1.0
2) Made a metadata change in my 10.1.2.4 client.
3) Connected to the 10.1.1.0 database with 10.1.2.4 and saw that there was no change to the stored prepared statements in SYS.SYSSTATEMENTS

I also confirmed that a database created with 10.1.2.4 does not get changed when reverting to 10.1.1.0.

Below this line is some history and reference that might be helful to someone fixing this issue:
------------------------------------------------------------------------------------------------------------------------------------------------
In discussing DERBY-970, the subject of the metadata stored prepared statements
came up.
The general questions are:

1) Why do we use stored prepared statements for metadata queries?
2) What issues might there be related to upgrade/downgrade with the
metadata stored prepared statements?
3) How do we address potential upgrade/downgrade issues?

GENERAL HISTORY:

• Cloudscape 5.x had stored prepared statements, a way to store precompiled
  statements in the database. This is no longer exposed externally.
• Metadata stored prepared statements were a performance optimization that
  predated the statement cache.
• In the past, this performance optimization has been of particular importance
  to gui database browsers that execute all the metadata methods on connection to
  the database. This would still probably be an issue with embedded even with the
  statement cache.
• All stored prepared statements get recompiled on the first connection to the
  database if the version changes.

UPGRADE HISTORY

• In Cloudscape 5.1, the metadata stored prepared statements have traditionally
  been a source of trouble for even minor version changes as queries change or
  they refer to methods/stored procedures that may or may not exist in the target
  version and cannot recompile or execute.
• The solution to the problem in Cloudscape v5.1.60 was to automatically
  always call DD_Version.dropJDBCMetadataSPSes() whenever the version changed up
  or down in upgradeIfNeeded().
• The workaround before this change to do this automatically was to call this
  method manually:

  CALL Factory.getDatabaseOfConnection(). dropAllJDBCMetaDataSPSes()

HOW DERBY WORKS TODAY:

• In Derby we now only call dropJDBCMetadataSPSes() on fullUpgrade and it has
  been this way since contribution.
• I think the problems of upgrade/downgrade for metadata stored prepared
  statements may exist in Derby.
• I don't know a workaround to drop the metadata stored prepared statements if
  we need to deliver a bug fix or how the ugprade/downgrade is handled currently.
• I seem to recall some special handling in Derby for soft upgrade for optimizer directives, but don't know the details.

RECENT DISCUSSIONS:
In discussing DERBY-970, the subject of the metadata stored prepared statements
came up.
The general questions are:

1) Why do we use stored prepared statements for metadata queries?
2) What issues might there be related to upgrade/downgrade with the
metadata stored prepared statements?
3) How do we address potential upgrade/downgrade issues?

MY QUESTIONS
Anyone know when/why the dropJDBCMetadataSPSes() on all version changes was
removed between Cloudcape 5.1.60 and contribution?
How do we deliver bug fixes for metadata queries or handle changes in the
metadata queries in Derby?

Issue Links

• is depended upon by: DERBY-3933 Reference Manual: document new SYSCS_UTIL.SYSCS_UPDATE_METADATA_QUERIES() system procedure
• is related to: DERBY-3000 getTables() call with 10.3 causes java.sql.SQLException: The parameter position '8' is out of range. The number of parameters for this prepared statement is '7'.