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987 lines
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987 lines
37 KiB
Plaintext
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TODO list for PostgreSQL
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========================
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Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
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Last updated: Wed Mar 16 23:42:00 EST 2005
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The most recent version of this document can be viewed at the PostgreSQL web
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site, http://www.PostgreSQL.org.
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#A hyphen, "-", marks changes that will appear in the upcoming 8.1 release.#
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Bracketed items, "[]", have more detail.
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This list contains all known PostgreSQL bugs and feature requests. If
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you would like to work on an item, please read the Developer's FAQ
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first.
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Administration
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==============
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* Remove behavior of postmaster -o after making postmaster/postgres
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flags unique
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* Allow limits on per-db/user connections
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* Add group object ownership, so groups can rename/drop/grant on objects,
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so we can implement roles
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* Allow server log information to be output as INSERT statements
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This would allow server log information to be easily loaded into
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a database for analysis.
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* Prevent default re-use of sysids for dropped users and groups
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Currently, if a user is removed while he still owns objects, a new
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user given might be given their user id and inherit the
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previous users objects.
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* Prevent dropping user that still owns objects, or auto-drop the objects
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* Allow pooled connections to list all prepared queries
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This would allow an application inheriting a pooled connection to know
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the queries prepared in the current session.
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* Allow major upgrades without dump/reload, perhaps using pg_upgrade
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* Have SHOW ALL and pg_settings show descriptions for server-side variables
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* Allow GRANT/REVOKE permissions to be applied to all schema objects with one
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command
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The proposed syntax is:
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GRANT SELECT ON ALL TABLES IN public TO phpuser;
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GRANT SELECT ON NEW TABLES IN public TO phpuser;
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* Allow GRANT/REVOKE permissions to be inherited by objects based on
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schema permissions
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* Remove unreferenced table files created by transactions that were
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in-progress when the server terminated abruptly
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* Allow reporting of which objects are in which tablespaces
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This item is difficult because a tablespace can contain objects from
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multiple databases. There is a server-side function that returns the
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databases which use a specific tablespace, so this requires a tool
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that will call that function and connect to each database to find the
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objects in each database for that tablespace.
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* Allow a database in tablespace t1 with tables created in tablespace t2
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to be used as a template for a new database created with default
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tablespace t2
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All objects in the default database tablespace must have default tablespace
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specifications. This is because new databases are created by copying
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directories. If you mix default tablespace tables and tablespace-specified
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tables in the same directory, creating a new database from such a mixed
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directory would create a new database with tables that had incorrect
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explicit tablespaces. To fix this would require modifying pg_class in the
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newly copied database, which we don't currently do.
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* Add a GUC variable to control the tablespace for temporary objects and
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sort files
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It could start with a random tablespace from a supplied list and cycle
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through the list.
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* Add "include file" functionality in postgresql.conf
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* Add session start time and last statement time to pg_stat_activity
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* Allow server logs to be remotely read using SQL commands
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* Allow pg_hba.conf settings to be controlled via SQL
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This would require a new global table that is dumped to flat file for
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use by the postmaster. We do a similar thing for pg_shadow currently.
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* Allow administrators to safely terminate individual sessions
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Right now, SIGTERM will terminate a session, but it is treated as
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though the postmaster has paniced and shared memory might not be
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cleaned up properly. A new signal is needed for safe termination.
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* Un-comment all variables in postgresql.conf
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By not showing commented-out variables, we discourage people from
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thinking that re-commenting a variable returns it to its default.
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This has to address environment variables that are then overridden
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by config file values. Another option is to allow commented values
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to return to their default values.
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* Allow point-in-time recovery to archive partially filled write-ahead
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logs
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Currently only full WAL files are archived. This means that the most
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recent transactions aren't available for recovery in case of a disk
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failure.
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* Create dump tool for write-ahead logs for use in determining
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transaction id for point-in-time recovery
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* Set proper permissions on non-system schemas during db creation
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Currently all schemas are owned by the super-user because they are
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copied from the template1 database.
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* Add a function that returns the 'uptime' of the postmaster
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* Allow a warm standby system to also allow read-only queries
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This is useful for checking PITR recovery.
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* Allow the PITR process to be debugged and data examined
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* Allow a warm standby system to also allow read-only queries
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* Add the client IP address and port to pg_stat_activity
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* Improve replication solutions
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o Load balancing
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You can use any of the master/slave replication servers to use a
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standby server for data warehousing. To allow read/write queries to
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multiple servers, you need multi-master replication like pgcluster.
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o Allow replication over unreliable or non-persistent links
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Data Types
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==========
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* Remove Money type, add money formatting for decimal type
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* Change NUMERIC to enforce the maximum precision, and increase it
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* Add function to return compressed length of TOAST data values
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* Allow INET subnet tests using non-constants to be indexed
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* Add transaction_timestamp(), statement_timestamp(), clock_timestamp()
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functionality
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Current CURRENT_TIMESTAMP returns the start time of the current
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transaction, and gettimeofday() returns the wallclock time. This will
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make time reporting more consistent and will allow reporting of
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the statement start time.
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* Have sequence dependency track use of DEFAULT sequences,
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seqname.nextval (?)
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* Disallow changing default expression of a SERIAL column (?)
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* Allow infinite dates just like infinite timestamps
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* Have initdb set DateStyle based on locale?
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* Add pg_get_acldef(), pg_get_typedefault(), and pg_get_attrdef()
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* Allow to_char() to print localized month names
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* Allow functions to have a schema search path specified at creation time
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* Allow substring/replace() to get/set bit values
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* Add a GUC variable to allow output of interval values in ISO8601 format
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* Fix data types where equality comparison isn't intuitive, e.g. box
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* Merge hardwired timezone names with the TZ database; allow either kind
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everywhere a TZ name is currently taken
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* Allow customization of the known set of TZ names (generalize the
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present australian_timezones hack)
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* Allow TIMESTAMP WITH TIME ZONE to store the original timezone
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information, either zone name or offset from UTC
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If the TIMESTAMP value is stored with a time zone name, interval
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computations should adjust based on the time zone rules, e.g. adding
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24 hours to a timestamp would yield a different result from adding one
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day.
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* Prevent INET cast to CIDR if the unmasked bits are not zero, or
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zero the bits
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* Prevent INET cast to CIDR from droping netmask, SELECT '1.1.1.1'::inet::cidr
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* Add 'tid != tid ' operator for use in corruption recovery
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* ARRAYS
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o Allow NULLs in arrays
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o Allow MIN()/MAX() on arrays
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o Delay resolution of array expression's data type so assignment
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coercion can be performed on empty array expressions
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o Modify array literal representation to handle array index lower bound
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of other than one
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* BINARY DATA
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o Improve vacuum of large objects, like /contrib/vacuumlo (?)
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o Add security checking for large objects
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Currently large objects entries do not have owners. Permissions can
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only be set at the pg_largeobject table level.
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o Auto-delete large objects when referencing row is deleted
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o Allow read/write into TOAST values like large objects
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This requires the TOAST column to be stored EXTERNAL.
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Multi-Language Support
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======================
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* Add NCHAR (as distinguished from ordinary varchar),
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* Allow locale to be set at database creation
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Currently locale can only be set during initdb.
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* Allow encoding on a per-column basis
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Right now only one encoding is allowed per database.
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* Optimize locale to have minimal performance impact when not used
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* Support multiple simultaneous character sets, per SQL92
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* Improve UTF8 combined character handling (?)
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* Add octet_length_server() and octet_length_client()
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* Make octet_length_client() the same as octet_length()?
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Views / Rules
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=============
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* Automatically create rules on views so they are updateable, per SQL99
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We can only auto-create rules for simple views. For more complex
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cases users will still have to write rules.
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* Add the functionality for WITH CHECK OPTION clause of CREATE VIEW
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* Allow NOTIFY in rules involving conditionals
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* Have views on temporary tables exist in the temporary namespace
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* Allow temporary views on non-temporary tables
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* Allow RULE recompilation
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Indexes
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=======
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* Allow inherited tables to inherit index, UNIQUE constraint, and primary
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key, foreign key
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* UNIQUE INDEX on base column not honored on INSERTs/UPDATEs from
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inherited table: INSERT INTO inherit_table (unique_index_col) VALUES
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(dup) should fail
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The main difficulty with this item is the problem of creating an index
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that can span more than one table.
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* Add UNIQUE capability to non-btree indexes
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* Add rtree index support for line, lseg, path, point
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* Use indexes for MIN() and MAX()
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MIN/MAX queries can already be rewritten as SELECT col FROM tab ORDER
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BY col {DESC} LIMIT 1. Completing this item involves doing this
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transformation automatically.
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* Use index to restrict rows returned by multi-key index when used with
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non-consecutive keys to reduce heap accesses
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For an index on col1,col2,col3, and a WHERE clause of col1 = 5 and
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col3 = 9, spin though the index checking for col1 and col3 matches,
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rather than just col1; also called skip-scanning.
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* Prevent index uniqueness checks when UPDATE does not modify the column
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Uniqueness (index) checks are done when updating a column even if the
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column is not modified by the UPDATE.
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* Fetch heap pages matching index entries in sequential order
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Rather than randomly accessing heap pages based on index entries, mark
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heap pages needing access in a bitmap and do the lookups in sequential
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order. Another method would be to sort heap ctids matching the index
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before accessing the heap rows.
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* Allow non-bitmap indexes to be combined by creating bitmaps in memory
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Bitmap indexes index single columns that can be combined with other bitmap
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indexes to dynamically create a composite index to match a specific query.
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Each index is a bitmap, and the bitmaps are bitwise AND'ed or OR'ed to be
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combined. They can index by tid or can be lossy requiring a scan of the
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heap page to find matching rows, or perhaps use a mixed solution where
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tids are recorded for pages with only a few matches and per-page bitmaps
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are used for more dense pages. Another idea is to use a 32-bit bitmap
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for every page and set a bit based on the item number mod(32).
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* Allow the creation of on-disk bitmap indexes which can be quickly
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combined with other bitmap indexes
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Such indexes could be more compact if there are only a few distinct values.
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Such indexes can also be compressed. Keeping such indexes updated can be
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costly.
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* Allow use of indexes to search for NULLs
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One solution is to create a partial index on an IS NULL expression.
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* Add concurrency to GIST
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* Pack hash index buckets onto disk pages more efficiently
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Currently no only one hash bucket can be stored on a page. Ideally
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several hash buckets could be stored on a single page and greater
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granularity used for the hash algorithm.
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* Allow accurate statistics to be collected on indexes with more than
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one column or expression indexes, perhaps using per-index statistics
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* Add fillfactor to control reserved free space during index creation
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* Allow the creation of indexes with mixed ascending/descending specifiers
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Commands
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========
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* Add BETWEEN ASYMMETRIC/SYMMETRIC
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* Change LIMIT/OFFSET and FETCH/MOVE to use int8
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* Allow CREATE TABLE AS to determine column lengths for complex
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expressions like SELECT col1 || col2
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* Allow UPDATE to handle complex aggregates [update] (?)
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* Allow backslash handling in quoted strings to be disabled for portability
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The use of C-style backslashes (.e.g. \n, \r) in quoted strings is not
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SQL-spec compliant, so allow such handling to be disabled. However,
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disabling backslashes could break many third-party applications and tools.
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* Allow an alias to be provided for the target table in UPDATE/DELETE
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This is not SQL-spec but many DBMSs allow it.
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* Allow additional tables to be specified in DELETE for joins
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UPDATE already allows this (UPDATE...FROM) but we need similar
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functionality in DELETE. It's been agreed that the keyword should
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be USING, to avoid anything as confusing as DELETE FROM a FROM b.
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* Add CORRESPONDING BY to UNION/INTERSECT/EXCEPT
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* Allow REINDEX to rebuild all database indexes, remove /contrib/reindex
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* Add ROLLUP, CUBE, GROUPING SETS options to GROUP BY
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* Add a schema option to createlang
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* Allow UPDATE tab SET ROW (col, ...) = (...) for updating multiple columns
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* Allow SET CONSTRAINTS to be qualified by schema/table name
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* Allow TRUNCATE ... CASCADE/RESTRICT
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* Allow PREPARE of cursors
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* Allow PREPARE to automatically determine parameter types based on the SQL
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statement
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* Allow finer control over the caching of prepared query plans
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Currently, queries prepared via the libpq API are planned on first
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execute using the supplied parameters --- allow SQL PREPARE to do the
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same. Also, allow control over replanning prepared queries either
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manually or automatically when statistics for execute parameters
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differ dramatically from those used during planning.
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* Allow LISTEN/NOTIFY to store info in memory rather than tables?
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Currently LISTEN/NOTIFY information is stored in pg_listener. Storing
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such information in memory would improve performance.
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* Dump large object comments in custom dump format
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* Add optional textual message to NOTIFY
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This would allow an informational message to be added to the notify
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message, perhaps indicating the row modified or other custom
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information.
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* Use more reliable method for CREATE DATABASE to get a consistent copy
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of db?
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Currently the system uses the operating system COPY command to create
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a new database.
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* Add C code to copy directories for use in creating new databases
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* Have pg_ctl look at PGHOST in case it is a socket directory?
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* Allow column-level GRANT/REVOKE privileges
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* Add a GUC variable to warn about non-standard SQL usage in queries
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* Add MERGE command that does UPDATE/DELETE, or on failure, INSERT (rules,
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triggers?)
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* Add ON COMMIT capability to CREATE TABLE AS SELECT
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* Add NOVICE output level for helpful messages like automatic sequence/index
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creation
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* Add COMMENT ON for all cluster global objects (users, groups, databases
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and tablespaces)
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* Add an option to automatically use savepoints for each statement in a
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multi-statement transaction.
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When enabled, this would allow errors in multi-statement transactions
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to be automatically ignored.
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* Make row-wise comparisons work per SQL spec
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* Add RESET CONNECTION command to reset all session state
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This would include resetting of all variables (RESET ALL), dropping of
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all temporary tables, removal of any NOTIFYs, cursors, prepared
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queries(?), currval()s, etc. This could be used for connection pooling.
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We could also change RESET ALL to have this functionality.
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* Allow FOR UPDATE queries to do NOWAIT locks
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* ALTER
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o Have ALTER TABLE RENAME rename SERIAL sequence names
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o Add ALTER DOMAIN TYPE
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o Allow ALTER TABLE ... ALTER CONSTRAINT ... RENAME
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o Allow ALTER TABLE to change constraint deferrability and actions
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o Disallow dropping of an inherited constraint
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o Allow objects to be moved to different schemas
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o Allow ALTER TABLESPACE to move to different directories
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o Allow databases and schemas to be moved to different tablespaces
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One complexity is whether moving a schema should move all existing
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schema objects or just define the location for future object creation.
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o Allow moving system tables to other tablespaces, where possible
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Currently non-global system tables must be in the default database
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schema. Global system tables can never be moved.
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* CLUSTER
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o Automatically maintain clustering on a table
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This might require some background daemon to maintain clustering
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during periods of low usage. It might also require tables to be only
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paritally filled for easier reorganization. Another idea would
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be to create a merged heap/index data file so an index lookup would
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automatically access the heap data too. A third idea would be to
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store heap rows in hashed groups, perhaps using a user-supplied
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hash function.
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o Add default clustering to system tables
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To do this, determine the ideal cluster index for each system
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table and set the cluster setting during initdb.
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* COPY
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o Allow COPY to report error lines and continue
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This requires the use of a savepoint before each COPY line is
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processed, with ROLLBACK on COPY failure.
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o Allow COPY to understand \x as a hex byte
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o Have COPY return the number of rows loaded/unloaded (?)
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o Allow COPY to optionally include column headings in the first line
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o -Allow COPY FROM ... CSV to interpret newlines and carriage
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returns in data
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* CURSOR
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o Allow UPDATE/DELETE WHERE CURRENT OF cursor
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This requires using the row ctid to map cursor rows back to the
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original heap row. This become more complicated if WITH HOLD cursors
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are to be supported because WITH HOLD cursors have a copy of the row
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and no FOR UPDATE lock.
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o Prevent DROP TABLE from dropping a row referenced by its own open
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cursor (?)
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o Allow pooled connections to list all open WITH HOLD cursors
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Because WITH HOLD cursors exist outside transactions, this allows
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them to be listed so they can be closed.
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* INSERT
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o Allow INSERT/UPDATE of the system-generated oid value for a row
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o Allow INSERT INTO tab (col1, ..) VALUES (val1, ..), (val2, ..)
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o Allow INSERT/UPDATE ... RETURNING new.col or old.col
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This is useful for returning the auto-generated key for an INSERT.
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One complication is how to handle rules that run as part of
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the insert.
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* SHOW/SET
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o Add SET PERFORMANCE_TIPS option to suggest INDEX, VACUUM, VACUUM
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ANALYZE, and CLUSTER
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o Add SET PATH for schemas (?)
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This is basically the same as SET search_path.
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o Prevent conflicting SET options from being set
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This requires a checking function to be called after the server
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configuration file is read.
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* SERVER-SIDE LANGUAGES
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o Allow PL/PgSQL's RAISE function to take expressions (?)
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Currently only constants are supported.
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o -Change PL/PgSQL to use palloc() instead of malloc()
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o Handle references to temporary tables that are created, destroyed,
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then recreated during a session, and EXECUTE is not used
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This requires the cached PL/PgSQL byte code to be invalidated when
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an object referenced in the function is changed.
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o Fix PL/pgSQL RENAME to work on variables other than OLD/NEW
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o Allow function parameters to be passed by name,
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get_employee_salary(emp_id => 12345, tax_year => 2001)
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o Add Oracle-style packages
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o Add table function support to pltcl, plperl, plpython (?)
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o Allow PL/pgSQL to name columns by ordinal position, e.g. rec.(3)
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o Allow PL/pgSQL EXECUTE query_var INTO record_var;
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o Add capability to create and call PROCEDURES
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o Allow PL/pgSQL to handle %TYPE arrays, e.g. tab.col%TYPE[]
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Clients
|
|
=======
|
|
|
|
* Add XML output to pg_dump and COPY
|
|
|
|
We already allow XML to be stored in the database, and XPath queries
|
|
can be used on that data using /contrib/xml2. It also supports XSLT
|
|
transformations.
|
|
|
|
* Add a libpq function to support Parse/DescribeStatement capability
|
|
* Prevent libpq's PQfnumber() from lowercasing the column name (?)
|
|
* Allow libpq to access SQLSTATE so pg_ctl can test for connection failure
|
|
|
|
This would be used for checking if the server is up.
|
|
|
|
* Have psql show current values for a sequence
|
|
* Move psql backslash database information into the backend, use mnemonic
|
|
commands? [psql]
|
|
|
|
This would allow non-psql clients to pull the same information out of
|
|
the database as psql.
|
|
|
|
* Fix psql's display of schema information (Neil)
|
|
* Allow psql \pset boolean variables to set to fixed values, rather than toggle
|
|
* Consistently display privilege information for all objects in psql
|
|
* Improve psql's handling of multi-line queries
|
|
* pg_dump
|
|
o Have pg_dump use multi-statement transactions for INSERT dumps
|
|
o Allow pg_dump to use multiple -t and -n switches
|
|
|
|
This should be done by allowing a '-t schema.table' syntax.
|
|
|
|
o Add dumping of comments on composite type columns
|
|
o Add dumping of comments on index columns
|
|
o Replace crude DELETE FROM method of pg_dumpall for cleaning of
|
|
users and groups with separate DROP commands
|
|
o Add dumping and restoring of LOB comments
|
|
o Stop dumping CASCADE on DROP TYPE commands in clean mode
|
|
o Add full object name to the tag field. eg. for operators we need
|
|
'=(integer, integer)', instead of just '='.
|
|
o Add pg_dumpall custom format dumps.
|
|
|
|
This is probably best done by combining pg_dump and pg_dumpall
|
|
into a single binary.
|
|
|
|
o Add CSV output format
|
|
|
|
* ECPG
|
|
o Docs
|
|
|
|
Document differences between ecpg and the SQL standard and
|
|
information about the Informix-compatibility module.
|
|
|
|
o Solve cardinality > 1 for input descriptors / variables (?)
|
|
o Add a semantic check level, e.g. check if a table really exists
|
|
o fix handling of DB attributes that are arrays
|
|
o Use backend PREPARE/EXECUTE facility for ecpg where possible
|
|
o Implement SQLDA
|
|
o Fix nested C comments
|
|
o sqlwarn[6] should be 'W' if the PRECISION or SCALE value specified
|
|
o Make SET CONNECTION thread-aware, non-standard?
|
|
o Allow multidimensional arrays
|
|
* Add internationalized message strings
|
|
|
|
|
|
Referential Integrity
|
|
=====================
|
|
|
|
* Add MATCH PARTIAL referential integrity
|
|
* Add deferred trigger queue file
|
|
|
|
Right now all deferred trigger information is stored in backend
|
|
memory. This could exhaust memory for very large trigger queues.
|
|
This item involves dumping large queues into files.
|
|
|
|
* Implement dirty reads or shared row locks and use them in RI triggers
|
|
|
|
Adding shared locks requires recording the table/rows numbers in a
|
|
shared area, and this could potentially be a large amount of data.
|
|
One idea is to store the table/row numbers in a separate table and set
|
|
a bit on the row indicating looking in this new table is required to
|
|
find any shared row locks.
|
|
|
|
* Enforce referential integrity for system tables
|
|
* Change foreign key constraint for array -> element to mean element
|
|
in array (?)
|
|
* Allow DEFERRABLE UNIQUE constraints (?)
|
|
* Allow triggers to be disabled [trigger]
|
|
|
|
Currently the only way to disable triggers is to modify the system
|
|
tables.
|
|
|
|
* With disabled triggers, allow pg_dump to use ALTER TABLE ADD FOREIGN KEY
|
|
|
|
If the dump is known to be valid, allow foreign keys to be added
|
|
without revalidating the data.
|
|
|
|
* Allow statement-level triggers to access modified rows
|
|
* Support triggers on columns (Greg Sabino Mullane)
|
|
* Remove CREATE CONSTRAINT TRIGGER
|
|
|
|
This was used in older releases to dump referential integrity
|
|
constraints.
|
|
|
|
* Allow AFTER triggers on system tables
|
|
|
|
System tables are modified in many places in the backend without going
|
|
through the executor and therefore not causing triggers to fire. To
|
|
complete this item, the functions that modify system tables will have
|
|
to fire triggers.
|
|
|
|
|
|
Dependency Checking
|
|
===================
|
|
|
|
* Flush cached query plans when the dependent objects change
|
|
* Track dependencies in function bodies and recompile/invalidate
|
|
|
|
|
|
Exotic Features
|
|
===============
|
|
|
|
* Add SQL99 WITH clause to SELECT
|
|
* Add SQL99 WITH RECURSIVE to SELECT
|
|
* Add pre-parsing phase that converts non-ANSI syntax to supported
|
|
syntax
|
|
|
|
This could allow SQL written for other databases to run without
|
|
modification.
|
|
|
|
* Allow plug-in modules to emulate features from other databases
|
|
* SQL*Net listener that makes PostgreSQL appear as an Oracle database
|
|
to clients
|
|
* Allow queries across databases or servers with transaction
|
|
semantics
|
|
|
|
Right now contrib/dblink can be used to issue such queries except it
|
|
does not have locking or transaction semantics. Two-phase commit is
|
|
needed to enable transaction semantics.
|
|
|
|
* Add two-phase commit
|
|
|
|
This will involve adding a way to respond to commit failure by either
|
|
taking the server into offline/readonly mode or notifying the
|
|
administrator
|
|
|
|
|
|
PERFORMANCE
|
|
===========
|
|
|
|
|
|
Fsync
|
|
=====
|
|
|
|
* Improve commit_delay handling to reduce fsync()
|
|
* Determine optimal fdatasync/fsync, O_SYNC/O_DSYNC options
|
|
* Allow multiple blocks to be written to WAL with one write()
|
|
* Add an option to sync() before fsync()'ing checkpoint files
|
|
|
|
|
|
Cache
|
|
=====
|
|
* Allow free-behind capability for large sequential scans, perhaps using
|
|
posix_fadvise()
|
|
|
|
Posix_fadvise() can control both sequential/random file caching and
|
|
free-behind behavior, but it is unclear how the setting affects other
|
|
backends that also have the file open, and the feature is not supported
|
|
on all operating systems.
|
|
|
|
* Consider use of open/fcntl(O_DIRECT) to minimize OS caching,
|
|
especially for WAL writes
|
|
* -Cache last known per-tuple offsets to speed long tuple access
|
|
* Speed up COUNT(*)
|
|
|
|
We could use a fixed row count and a +/- count to follow MVCC
|
|
visibility rules, or a single cached value could be used and
|
|
invalidated if anyone modifies the table. Another idea is to
|
|
get a count directly from a unique index, but for this to be
|
|
faster than a sequential scan it must avoid access to the heap
|
|
to obtain tuple visibility information.
|
|
|
|
* Allow data to be pulled directly from indexes
|
|
|
|
Currently indexes do not have enough tuple tuple visibility
|
|
information to allow data to be pulled from the index without
|
|
also accessing the heap. One way to allow this is to set a bit
|
|
to index tuples to indicate if a tuple is currently visible to
|
|
all transactions when the first valid heap lookup happens. This
|
|
bit would have to be cleared when a heap tuple is expired.
|
|
|
|
* Consider automatic caching of queries at various levels:
|
|
o Parsed query tree
|
|
o Query execute plan
|
|
o Query results
|
|
|
|
* Allow the size of the buffer cache used by temporary objects to be
|
|
specified as a GUC variable
|
|
|
|
Larger local buffer cache sizes requires more efficient handling of
|
|
local cache lookups.
|
|
|
|
* Improve the background writer
|
|
|
|
Allow the background writer to more efficiently write dirty buffers
|
|
from the end of the LRU cache and use a clock sweep algorithm to
|
|
write other dirty buffers to reduced checkpoint I/O
|
|
|
|
* Allow sequential scans to take advantage of other concurrent
|
|
sequentiqal scans, also called "Synchronised Scanning"
|
|
|
|
Vacuum
|
|
======
|
|
|
|
* Improve speed with indexes
|
|
|
|
For large table adjustements during vacuum, it is faster to reindex
|
|
rather than update the index.
|
|
|
|
* Reduce lock time by moving tuples with read lock, then write
|
|
lock and truncate table
|
|
|
|
Moved tuples are invisible to other backends so they don't require a
|
|
write lock. However, the read lock promotion to write lock could lead
|
|
to deadlock situations.
|
|
|
|
* -Add a warning when the free space map is too small
|
|
* Maintain a map of recently-expired rows
|
|
|
|
This allows vacuum to reclaim free space without requiring
|
|
a sequential scan
|
|
|
|
* Auto-vacuum
|
|
o Move into the backend code
|
|
o Scan the buffer cache to find free space or use background writer
|
|
o Use free-space map information to guide refilling
|
|
|
|
Locking
|
|
=======
|
|
|
|
* Make locking of shared data structures more fine-grained
|
|
|
|
This requires that more locks be acquired but this would reduce lock
|
|
contention, improving concurrency.
|
|
|
|
* Add code to detect an SMP machine and handle spinlocks accordingly
|
|
from distributted.net, http://www1.distributed.net/source,
|
|
in client/common/cpucheck.cpp
|
|
|
|
On SMP machines, it is possible that locks might be released shortly,
|
|
while on non-SMP machines, the backend should sleep so the process
|
|
holding the lock can complete and release it.
|
|
|
|
* Improve SMP performance on i386 machines
|
|
|
|
i386-based SMP machines can generate excessive context switching
|
|
caused by lock failure in high concurrency situations. This may be
|
|
caused by CPU cache line invalidation inefficiencies.
|
|
|
|
* Research use of sched_yield() for spinlock acquisition failure
|
|
* Fix priority ordering of read and write light-weight locks (Neil)
|
|
|
|
|
|
Startup Time
|
|
============
|
|
|
|
* Experiment with multi-threaded backend [thread]
|
|
|
|
This would prevent the overhead associated with process creation. Most
|
|
operating systems have trivial process creation time compared to
|
|
database startup overhead, but a few operating systems (WIn32,
|
|
Solaris) might benefit from threading.
|
|
|
|
* Add connection pooling
|
|
|
|
It is unclear if this should be done inside the backend code or done
|
|
by something external like pgpool. The passing of file descriptors to
|
|
existing backends is one of the difficulties with a backend approach.
|
|
|
|
|
|
Write-Ahead Log
|
|
===============
|
|
|
|
* Eliminate need to write full pages to WAL before page modification [wal]
|
|
|
|
Currently, to protect against partial disk page writes, we write the
|
|
full page images to WAL before they are modified so we can correct any
|
|
partial page writes during recovery. These pages can also be
|
|
eliminated from point-in-time archive files.
|
|
|
|
* Reduce WAL traffic so only modified values are written rather than
|
|
entire rows (?)
|
|
* Turn off after-change writes if fsync is disabled
|
|
|
|
If fsync is off, there is no purpose in writing full pages to WAL
|
|
|
|
* Add WAL index reliability improvement to non-btree indexes
|
|
* Allow the pg_xlog directory location to be specified during initdb
|
|
with a symlink back to the /data location
|
|
* Allow WAL information to recover corrupted pg_controldata
|
|
* Find a way to reduce rotational delay when repeatedly writing
|
|
last WAL page
|
|
|
|
Currently fsync of WAL requires the disk platter to perform a full
|
|
rotation to fsync again. One idea is to write the WAL to different
|
|
offsets that might reduce the rotational delay.
|
|
|
|
* Allow buffered WAL writes and fsync
|
|
|
|
Instead of guaranteeing recovery of all committed transactions, this
|
|
would provide improved performance by delaying WAL writes and fsync
|
|
so an abrupt operating system restart might lose a few seconds of
|
|
committed transactions but still be consistent. We could perhaps
|
|
remove the 'fsync' parameter (which results in an an inconsistent
|
|
database) in favor of this capability.
|
|
|
|
* Eliminate WAL logging for CREATE TABLE AS when not doing WAL archiving
|
|
|
|
Optimizer / Executor
|
|
====================
|
|
|
|
* Add missing optimizer selectivities for date, r-tree, etc
|
|
* Allow ORDER BY ... LIMIT 1 to select high/low value without sort or
|
|
index using a sequential scan for highest/lowest values
|
|
|
|
If only one value is needed, there is no need to sort the entire
|
|
table. Instead a sequential scan could get the matching value.
|
|
|
|
* Precompile SQL functions to avoid overhead
|
|
* Create utility to compute accurate random_page_cost value
|
|
* Improve ability to display optimizer analysis using OPTIMIZER_DEBUG
|
|
* Have EXPLAIN ANALYZE highlight poor optimizer estimates
|
|
* Use CHECK constraints to influence optimizer decisions
|
|
|
|
CHECK constraints contain information about the distribution of values
|
|
within the table. This is also useful for implementing subtables where
|
|
a tables content is distributed across several subtables.
|
|
|
|
* Consider using hash buckets to do DISTINCT, rather than sorting
|
|
|
|
This would be beneficial when there are few distinct values.
|
|
|
|
* ANALYZE should record a pg_statistic entry for an all-NULL column
|
|
|
|
Miscellaneous
|
|
=============
|
|
|
|
* Do async I/O for faster random read-ahead of data
|
|
|
|
Async I/O allows multiple I/O requests to be sent to the disk with
|
|
results coming back asynchronously.
|
|
|
|
* Use mmap() rather than SYSV shared memory or to write WAL files (?)
|
|
|
|
This would remove the requirement for SYSV SHM but would introduce
|
|
portability issues. Anonymous mmap (or mmap to /dev/zero) is required
|
|
to prevent I/O overhead.
|
|
|
|
* Consider mmap()'ing files into a backend?
|
|
|
|
Doing I/O to large tables would consume a lot of address space or
|
|
require frequent mapping/unmapping. Extending the file also causes
|
|
mapping problems that might require mapping only individual pages,
|
|
leading to thousands of mappings. Another problem is that there is no
|
|
way to _prevent_ I/O to disk from the dirty shared buffers so changes
|
|
could hit disk before WAL is written.
|
|
|
|
* Add a script to ask system configuration questions and tune postgresql.conf
|
|
* Use a phantom command counter for nested subtransactions to reduce
|
|
per-tuple overhead
|
|
* Consider parallel processing a single query
|
|
|
|
This would involve using multiple threads or processes to do optimization,
|
|
sorting, or execution of single query. The major advantage of such a
|
|
feature would be to allow multiple CPUs to work together to process a
|
|
single query.
|
|
|
|
* Research the use of larger page sizes
|
|
|
|
|
|
Source Code
|
|
===========
|
|
|
|
* Add use of 'const' for variables in source tree
|
|
* Rename some /contrib modules from pg* to pg_*
|
|
* Move some things from /contrib into main tree
|
|
* Move some /contrib modules out to their own project sites
|
|
* Remove warnings created by -Wcast-align
|
|
* Move platform-specific ps status display info from ps_status.c to ports
|
|
* Add optional CRC checksum to heap and index pages
|
|
* Improve documentation to build only interfaces (Marc)
|
|
* Remove or relicense modules that are not under the BSD license, if possible
|
|
* Remove memory/file descriptor freeing before ereport(ERROR)
|
|
* Acquire lock on a relation before building a relcache entry for it
|
|
* Promote debug_query_string into a server-side function current_query()
|
|
* Allow the identifier length to be increased via a configure option
|
|
* Remove Win32 rename/unlink looping if unnecessary
|
|
* Remove kerberos4 from source tree?
|
|
* Allow cross-compiling by generating the zic database on the target system
|
|
* Improve NLS maintenace of libpgport messages linked onto applications
|
|
* Allow ecpg to work with MSVC and BCC
|
|
* -Make src/port/snprintf.c thread-safe
|
|
* Add xpath_array() to /contrib/xml2 to return results as an array
|
|
* Allow building in directories containing spaces
|
|
|
|
This is probably not possible because 'gmake' and other compiler tools
|
|
do not fully support quoting of paths with spaces.
|
|
|
|
* Allow installing to directories containing spaces
|
|
|
|
This is possible if proper quoting is added to the makefiles for the
|
|
install targets. Because PostgreSQL supports relocatable installs, it
|
|
is already possible to install into a directory that doesn't contain
|
|
spaces and then copy the install to a directory with spaces.
|
|
|
|
* Fix cross-compiling of time zone database via 'zic'
|
|
* Win32
|
|
o Remove configure.in check for link failure when cause is found
|
|
o Remove readdir() errno patch when runtime/mingwex/dirent.c rev
|
|
1.4 is released
|
|
o Remove psql newline patch when we find out why mingw outputs an
|
|
extra newline
|
|
o Allow psql to use readline once non-US code pages work with
|
|
backslashes
|
|
o Re-enable timezone output on log_line_prefix '%t' when a
|
|
shorter timezone string is available
|
|
o Improve dlerror() reporting string
|
|
o Fix problem with shared memory on the Win32 Terminal Server
|
|
o Add support for Unicode
|
|
|
|
To fix this, the data needs to be converted to/from UTF16/UTF8
|
|
so the Win32 wcscoll() can be used, and perhaps other functions
|
|
like towupper(). However, UTF8 already works with normal
|
|
locales but provides no ordering or character set classes.
|
|
|
|
* Wire Protocol Changes
|
|
o Allow dynamic character set handling
|
|
o Add decoded type, length, precision
|
|
o Use compression?
|
|
o Update clients to use data types, typmod, schema.table.column names
|
|
of result sets using new query protocol
|
|
|
|
|
|
---------------------------------------------------------------------------
|
|
|
|
|
|
Developers who have claimed items are:
|
|
--------------------------------------
|
|
* Alvaro is Alvaro Herrera <alvherre@dcc.uchile.cl>
|
|
* Andrew is Andrew Dunstan <andrew@dunslane.net>
|
|
* Bruce is Bruce Momjian <pgman@candle.pha.pa.us> of Software Research Assoc.
|
|
* Christopher is Christopher Kings-Lynne <chriskl@familyhealth.com.au> of
|
|
Family Health Network
|
|
* Claudio is Claudio Natoli <claudio.natoli@memetrics.com>
|
|
* D'Arcy is D'Arcy J.M. Cain <darcy@druid.net> of The Cain Gang Ltd.
|
|
* Fabien is Fabien Coelho <coelho@cri.ensmp.fr>
|
|
* Gavin is Gavin Sherry <swm@linuxworld.com.au> of Alcove Systems Engineering
|
|
* Greg is Greg Sabino Mullane <greg@turnstep.com>
|
|
* Hiroshi is Hiroshi Inoue <Inoue@tpf.co.jp>
|
|
* Jan is Jan Wieck <JanWieck@Yahoo.com> of Afilias, Inc.
|
|
* Joe is Joe Conway <mail@joeconway.com>
|
|
* Karel is Karel Zak <zakkr@zf.jcu.cz>
|
|
* Magnus is Magnus Hagander <mha@sollentuna.net>
|
|
* Marc is Marc Fournier <scrappy@hub.org> of PostgreSQL, Inc.
|
|
* Matthew T. O'Connor <matthew@zeut.net>
|
|
* Michael is Michael Meskes <meskes@postgresql.org> of Credativ
|
|
* Neil is Neil Conway <neilc@samurai.com>
|
|
* Oleg is Oleg Bartunov <oleg@sai.msu.su>
|
|
* Peter is Peter Eisentraut <peter_e@gmx.net>
|
|
* Philip is Philip Warner <pjw@rhyme.com.au> of Albatross Consulting Pty. Ltd.
|
|
* Rod is Rod Taylor <pg@rbt.ca>
|
|
* Simon is Simon Riggs <simon@2ndquadrant.com>
|
|
* Stephan is Stephan Szabo <sszabo@megazone23.bigpanda.com>
|
|
* Tatsuo is Tatsuo Ishii <t-ishii@sra.co.jp> of Software Research Assoc.
|
|
* Tom is Tom Lane <tgl@sss.pgh.pa.us> of Red Hat
|