Firebird Project is happy to announce general availability of Firebird 2.5.1 This sub-release introduces several bug fixes and many important improvements – for example, performance improvements during a database restore, the ability to write to global temporary tables in read-only databases, etc. For the full list of changes please refer to the Release Notes, Chapter 2 “New in Firebird 2.5″. Firebird 2.5.1 has 100% compatible on-disk structure with Firebird 2.5.0, so it is recommended to migrate to 2.5.1 as soon as possible.

There is a substantial number of bug fixes, this sub-release takes in a few minor improvements and optimizations that missed the initial release. In summary:

  • Significant for MacOSX 10.7 users was a bug that caused attempts to start Superserver and Superclassic to fail. The bug is described in Tracker ticket CORE-3589 and also in the Bug Fixes list for this sub-release.
  • An SQLSTATE context variable is now available in PSQL, parallel to the the context variables GDSCODE and SQLCODE that are used in WHEN blocks to test for error conditions.
  • A couple of improvements were made, that should help performance when global temporary tables (GTTs) are being used:
    • The “undoing”, on rolling back the transaction, of changes made to GTTs that were created with the ON COMMIT DELETE ROWS option was an unnecessary overhead and has been bypassed.
    • Garbage collection in global temporary tables was being delayed unnecessarily by active transactions in other attachments. That bottleneck is gone.
  • A needed optimization in the temporary space manager with regard to small chunk allocations has been implemented.
  • The Lock Manager has been provided with the capability to cancel waiting, avoiding a condition whereby a transaction in WAIT mode could wait interminably for the end of another transaction that could not be achieved by either a DELETE FROM MON$xxx or an fb_cancel_operation request.
  • The query optimizer now estimates the actual record compression ratio, enabling better guesses about the number of stored records in tables.
  • Some minor improvements to the remote interface:
    • Any unused bytes of varchar values in the message buffer are now set to zero.
    • Set the SO_KEEPALIVE option on the client TCP socket
  • The MON$STATEMENT_ID value constant is now kept constant among monitoring snapshots.
  • Ports of this sub-release were done for Linux/HPPA and Linux/alpha platforms.
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