PostgreSQL 8.1 was recently released with hundreds of changes and new features including: 1) Bitmap scans allow using more than one index per table by combining index hits in memory. 2) Two-phase commit support allows prepared transactions to be preserved across server restarts. 3) The new role system unifies users and groups and roles can own database objects. 4) Constraint exclusion avoids lookups on child tables when constraints make rows impossible.

1. PostgreSQL News
Peter Eisentraut
petere@postgresql.org

2. News
• PostgreSQL 8.1 released today
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3. Hundreds of Changes
• See release notes for details...
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4. Bitmap Scans
• Ability to use more than one index per table
• Index hits are combined in memory
• Useful for
• SELECT * FROM table WHERE (x = 1) OR (x
= 2) OR (x = 3)
• Automatically generated queries
• Slony-I
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5. Two-Phase Commit
• PREPARE TRANSACTION
• COMMIT TRANSACTION
• ROLLBACK TRANSACTION
• Prepared transactions are preserved
across server restart.
• No XA interface support yet
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6. Role System
• Unifies users and groups
• “User” = role + login permission
• Roles can be nested
• Roles can own objects
• Roles can be enabled/disabled at run time
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7. Automatic Use of Indexes for
MIN() and MAX()
Rewrite
SELECT min(col) FROM tab;
as
SELECT col FROM tab ORDER BY col
LIMIT 1;
• Index automatically used
• Works for all data types
• Can be used by user-defined aggregates
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8. Integrated Autovacuum
• contrib/pg_autovacuum now a server
process
• Starts and stops with the database server
• Many configuration possibilities in
postgresql.conf
• Not turned on by default
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9. Shared Row-Level Locks
• SELECT ... FOR SHARE
• Reduces locking requirements of referential
integrity checks
• Better performance for foreign keys
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10. Dependencies on Shared
Objects
• Prevents roles from being dropped while
there are still database objects they own
• No more “orphaned” objects
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11. Constraint Exclusion
• Avoids lookups on child tables where
constraints indicate that no matching rows
exist in the child table.
• Basic type of table partitioning, to be
extended in the future
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12. New ODBC Driver
• Based on libpq
• IPv6 support
• SSL support
• A lot more stable
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13. New JDBC Driver
• Lots of bug fixes
• Is rumored to pass Sun JDBC CTS
• No XA yet :-(
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14. New pgAdmin III Version 1.4.0
• PostgreSQL 8.1 support:
• Autovacuum administration
• Roles
• OUT parameters
• Prepared transactions (2PC)
• Graphical EXPLAIN
• Slony-I support
• SQL/shell job scheduling agent
• Mac OS X support
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15. Future/Most Wanted Features
• MERGE command
• Table partitioning
• Materialized views
• Updatable views
• Index-organized tables, index-only access
• Recursive queries
• Window functions
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16. Questions?
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