Firebird 2.5

General

New Threading architecture, introducing the new SuperClassic server, for better SMP support
SQL CREATE/ALTER/DROP USER
ALTER VIEW and CREATE OR ALTER VIEW
Autonomous transactions within a PSQL module (stored procedure, trigger or dynamically executable PSQL block)
PSQL new ability to query another database via EXECUTE STATEMENT
Thread-safe client library
ODS version 11.2
Optimizer Improvements

System audit tracing and user trace sessions via the Services API, making it possible to monitor and analyse everything going on in a database in real time
New system role RDB$ADMIN allows SYSDBA to transfer its privileges to another user on a per-database basis (ODS 11.2)
More information in the monitoring tables
- MON$MEMORY_USAGE: current memory usage
- MON$CONTEXT_VARIABLES: known context variables
Asynchronous cancellation of connections
- Disconnect connection ID 32: DELETE FROM MON$STATEMENTS WHERE MON$ATTACHMENT_ID = 32
- Disconnect all clients except my own connection:
  DELETE FROM MON$ATTACHMENTS WHERE MON$ATTACHMENT_ID <> CURRENT_CONNECTION
Capability for ordinary users to monitor any of their own attachments as well as CURRENT_CONNECTION

Regular expression support using the SIMILAR TO predicate
ALTER COLUMN for computed columns
Enhanced access to stored procedures in view definitions
Optional GRANTED BY or GRANTED AS for GRANT and REVOKE statements, enabling the grantor to be a user other than the CURRENT_USER (the default)
REVOKE ALL syntax to dispose of all privileges for a user or role at once
Support for WHERE SOME_COL = ? OR ? IS NULL predications
Removal of “reserved” status for all but a handful of keywords that are not reserved in the SQL standard
Hex Literal Support: SELECT x'00F0A53BC7' FROM RDB$DATABASE;
Borrow Database Column Type for a PSQL Variable:
CREATE PROCEDURE SP_INS_PERSON (ID TYPE OF COLUMN PERSON.ID)
Well-formedness checks are now performed on UNICODE_FSS strings and text blobs

New built-in functions for converting UUID CHAR(16) OCTETS strings to RFC4122-compliant format and vice versa: CHAR_TO_UUID(), UUID_TO_CHAR()
Ability to pass 32-bit and 64-bit integers as hexadecimal in numeric literal and X-prefixed binary string literal formats

Default COLLATE clause for CREATE DATABASE
Ability to change the default COLLATE for a used character set
GBAK restore switches FIX_FSS_DATA and FIX_FSS_METADATA to restore legacy databases with UNICODE_FSS data and/or metadata correctly without resorting to scripts and manual techniques
Accent-insensitive collation for Unicode

New tool fbtracemgr
Retrieve password from a file or prompt: for all tools that expect a password parameter: -fet[ch_password] <filename> instead of -pa[ssword] <password>
GBAK: New repair switches for malformed strings

and many many more ...