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PostgreSQL TODO List
====================
Current maintainer: Bruce Momjian (bruce@momjian.us)
Last updated: Sat Mar 22 20:14:35 EDT 2008
The most recent version of this document can be viewed at
http://www.postgresql.org/docs/faqs.TODO.html.
#A hyphen, "-", marks changes that will appear in the upcoming 8.3 release.#
#A percent sign, "%", marks items that are easier to implement.#
Bracketed items, "[]", have more detail.
This list contains all known PostgreSQL bugs and feature requests. If
you would like to work on an item, please read the Developer's FAQ
first. There is also a developer's wiki at
http://developer.postgresql.org.
Administration
==============
* Allow administrators to safely terminate individual sessions either
via an SQL function or SIGTERM
Lock table corruption following SIGTERM of an individual backend
has been reported in 8.0. A possible cause was fixed in 8.1, but
it is unknown whether other problems exist. This item mostly
requires additional testing rather than of writing any new code.
http://archives.postgresql.org/pgsql-hackers/2006-08/msg00174.php
http://archives.postgresql.org/pgsql-hackers/2007-04/msg00218.php
* Check for unreferenced table files created by transactions that were
in-progress when the server terminated abruptly
http://archives.postgresql.org/pgsql-patches/2006-06/msg00096.php
* Set proper permissions on non-system schemas during db creation
Currently all schemas are owned by the super-user because they are copied
from the template1 database. However, since all objects are inherited
from the template database, it is not clear that setting schemas to the db
owner is correct.
* Add function to report the time of the most recent server reload
* Allow statistics collector information to be pulled from the collector
process directly, rather than requiring the collector to write a
filesystem file twice a second?
* Reduce file system activity overhead of statistics file pgstat.stat
http://archives.postgresql.org/pgsql-general/2007-12/msg00106.php
* Allow statistics last vacuum/analyze execution times to be displayed
without requiring stats_row_level to be enabled
* Allow log_min_messages to be specified on a per-module basis
This would allow administrators to see more detailed information from
specific sections of the backend, e.g. checkpoints, autovacuum, etc.
Another idea is to allow separate configuration files for each module,
or allow arbitrary SET commands to be passed to them.
* Simplify ability to create partitioned tables
This would allow creation of partitioned tables without requiring
creation of triggers or rules for INSERT/UPDATE/DELETE, and constraints
for rapid partition selection. Options could include range and hash
partition selection.
http://archives.postgresql.org/pgsql-hackers/2007-03/msg00375.php
http://archives.postgresql.org/pgsql-hackers/2007-04/msg00151.php
http://archives.postgresql.org/pgsql-hackers/2008-01/msg00028.php
http://archives.postgresql.org/pgsql-hackers/2008-01/msg00248.php
http://archives.postgresql.org/pgsql-hackers/2008-01/msg00387.php
http://archives.postgresql.org/pgsql-hackers/2008-01/msg00413.php
* Allow auto-selection of partitioned tables for min/max() operations
* Allow more complex user/database default GUC settings
Currently ALTER USER and ALTER DATABASE support per-user and
per-database defaults. Consider adding per-user-and-database
defaults so things like search_path can be defaulted for a
specific user connecting to a specific database.
* Allow custom variable classes that can restrict who can set the values
http://archives.postgresql.org/pgsql-hackers/2006-11/msg00911.php
* Implement the SQL standard mechanism whereby REVOKE ROLE revokes only
the privilege granted by the invoking role, and not those granted
by other roles
http://archives.postgresql.org/pgsql-bugs/2007-05/msg00010.php
* Allow SSL authentication/encryption over unix domain sockets
http://archives.postgresql.org/pgsql-hackers/2007-12/msg00924.php
* Allow SSL key file permission checks to be optionally disabled when
sharing SSL keys with other applications
http://archives.postgresql.org/pgsql-bugs/2007-12/msg00069.php
* Allow client certificate names to be checked against the client
hostname
This is already implemented in
libpq/fe-secure.c::verify_peer_name_matches_certificate() but the code
is commented out.
* Configuration files
o Allow pg_hba.conf to specify host names along with IP addresses
Host name lookup could occur when the postmaster reads the
pg_hba.conf file, or when the backend starts. Another
solution would be to reverse lookup the connection IP and
check that hostname against the host names in pg_hba.conf.
We could also then check that the host name maps to the IP
address.
o %Allow postgresql.conf file values to be changed via an SQL
API, perhaps using SET GLOBAL
o Allow the server to be stopped/restarted via an SQL API
o Issue a warning if a change-on-restart-only postgresql.conf value
is modified and the server config files are reloaded
o Consider normalizing fractions in postgresql.conf, perhaps
using '%'
http://archives.postgresql.org/pgsql-hackers/2007-06/msg00550.php
o Allow Kerberos to disable stripping of realms so we can
check the username@realm against multiple realms
http://archives.postgresql.org/pgsql-hackers/2007-11/msg00009.php
* Tablespaces
o Allow a database in tablespace t1 with tables created in
tablespace t2 to be used as a template for a new database created
with default tablespace t2
Currently all objects in the default database tablespace must
have default tablespace specifications. This is because new
databases are created by copying directories. If you mix default
tablespace tables and tablespace-specified tables in the same
directory, creating a new database from such a mixed directory
would create a new database with tables that had incorrect
explicit tablespaces. To fix this would require modifying
pg_class in the newly copied database, which we don't currently
do.
o Allow reporting of which objects are in which tablespaces
This item is difficult because a tablespace can contain objects
from multiple databases. There is a server-side function that
returns the databases which use a specific tablespace, so this
requires a tool that will call that function and connect to each
database to find the objects in each database for that tablespace.
o Allow WAL replay of CREATE TABLESPACE to work when the directory
structure on the recovery computer is different from the original
o Allow per-tablespace quotas
* Point-In-Time Recovery (PITR)
o Allow a warm standby system to also allow read-only statements
[pitr]
http://archives.postgresql.org/pgsql-hackers/2007-03/msg00050.php
o %Create dump tool for write-ahead logs for use in determining
transaction id for point-in-time recovery
This is useful for checking PITR recovery.
o Allow recovery.conf to support the same syntax as
postgresql.conf, including quoting
http://archives.postgresql.org/pgsql-hackers/2006-12/msg00497.php
o Fix server restart problem when the server was shutdown during
a PITR backup
http://archives.postgresql.org/pgsql-hackers/2007-11/msg00800.php
o Recreate pg_xlog/archive_status/ if it doesn't exist after
restoring from a PITR backup
http://archives.postgresql.org/pgsql-hackers/2007-12/msg00487.php
Data Types
==========
* Change NUMERIC to enforce the maximum precision
* Reduce storage space for small NUMERICs
http://archives.postgresql.org/pgsql-hackers/2007-02/msg01331.php
http://archives.postgresql.org/pgsql-patches/2007-02/msg00505.php
http://archives.postgresql.org/pgsql-hackers/2007-06/msg00715.php
* Fix data types where equality comparison isn't intuitive, e.g. box
* Add support for public SYNONYMs
http://archives.postgresql.org/pgsql-hackers/2006-03/msg00519.php
* Fix CREATE CAST on DOMAINs
http://archives.postgresql.org/pgsql-hackers/2006-05/msg00072.php
http://archives.postgresql.org/pgsql-hackers/2006-09/msg01681.php
* Allow domains to be cast
http://archives.postgresql.org/pgsql-hackers/2003-06/msg01206.php
http://archives.postgresql.org/pgsql-hackers/2007-08/msg00289.php
* Add support for SQL-standard GENERATED/IDENTITY columns
http://archives.postgresql.org/pgsql-hackers/2006-07/msg00543.php
http://archives.postgresql.org/pgsql-hackers/2006-08/msg00038.php
http://archives.postgresql.org/pgsql-hackers/2007-05/msg00344.php
http://archives.postgresql.org/pgsql-patches/2007-05/msg00076.php
http://archives.postgresql.org/pgsql-hackers/2008-02/msg00604.php
* Improve XML support
http://developer.postgresql.org/index.php/XML_Support
* Consider placing all sequences in a single table, or create a system
view
http://archives.postgresql.org/pgsql-hackers/2008-03/msg00008.php
* Allow the UUID type to accept non-standard formats
http://archives.postgresql.org/pgsql-hackers/2008-02/msg01214.php
* Allow text search dictionary to filter out only stop words
http://archives.postgresql.org/pgsql-patches/2007-11/msg00081.php
* Consider a function-based API for '@@' full text searches
http://archives.postgresql.org/pgsql-hackers/2007-11/msg00511.php
* Improve text search error messages
http://archives.postgresql.org/pgsql-hackers/2007-10/msg00966.php
http://archives.postgresql.org/pgsql-hackers/2007-11/msg01146.php
* Consider a special data type for regular expressions
http://archives.postgresql.org/pgsql-hackers/2007-08/msg01067.php
* Reduce BIT data type overhead using short varlena headers
http://archives.postgresql.org/pgsql-general/2007-12/msg00273.php
* Dates and Times
o Allow infinite dates and intervals just like infinite timestamps
o Merge hardwired timezone names with the TZ database; allow either
kind everywhere a TZ name is currently taken
o Allow TIMESTAMP WITH TIME ZONE to store the original timezone
information, either zone name or offset from UTC [timezone]
If the TIMESTAMP value is stored with a time zone name, interval
computations should adjust based on the time zone rules.
o Fix SELECT '0.01 years'::interval, '0.01 months'::interval
o Add a GUC variable to allow output of interval values in ISO8601
format
o Have timestamp subtraction not call justify_hours()?
http://archives.postgresql.org/pgsql-sql/2006-10/msg00059.php
o Improve timestamptz subtraction to be DST-aware
Currently subtracting one date from another that crosses a
daylight savings time adjustment can return '1 day 1 hour', but
adding that back to the first date returns a time one hour in
the future. This is caused by the adjustment of '25 hours' to
'1 day 1 hour', and '1 day' is the same time the next day, even
if daylight savings adjustments are involved.
o Fix interval display to support values exceeding 2^31 hours
o Add overflow checking to timestamp and interval arithmetic
o Extend timezone code to allow 64-bit values so we can
represent years beyond 2038
http://archives.postgresql.org/pgsql-hackers/2006-09/msg01363.php
o Use LC_TIME for localized weekday/month names, rather than
LC_MESSAGES
http://archives.postgresql.org/pgsql-hackers/2006-11/msg00390.php
o Add ISO INTERVAL handling
http://archives.postgresql.org/pgsql-hackers/2006-01/msg00250.php
http://archives.postgresql.org/pgsql-bugs/2006-04/msg00248.php
o Support ISO INTERVAL syntax if units cannot be determined from
the string, and are supplied after the string
The SQL standard states that the units after the string
specify the units of the string, e.g. INTERVAL '2' MINUTE
should return '00:02:00'. The current behavior has the units
restrict the interval value to the specified unit or unit
range, INTERVAL '70' SECOND returns '00:00:10'.
For syntax that isn't uniquely ISO or PG syntax, like '1' or
'1:30', treat as ISO if there is a range specification clause,
and as PG if there no clause is present, e.g. interpret '1:30'
MINUTE TO SECOND as '1 minute 30 seconds', and interpret
'1:30' as '1 hour, 30 minutes'.
This makes common cases like SELECT INTERVAL '1' MONTH
SQL-standard results. The SQL standard supports a limited
number of unit combinations and doesn't support unit names in
the string. The PostgreSQL syntax is more flexible in the
range of units supported, e.g. PostgreSQL supports '1 year 1
hour', while the SQL standard does not.
o Add support for year-month syntax, INTERVAL '50-6' YEAR
TO MONTH
o Interpret INTERVAL '1 year' MONTH as CAST (INTERVAL '1
year' AS INTERVAL MONTH), and this should return '12 months'
o Round or truncate values to the requested precision, e.g.
INTERVAL '11 months' AS YEAR should return one or zero
o Support precision, CREATE TABLE foo (a INTERVAL MONTH(3))
* Arrays
o Delay resolution of array expression's data type so assignment
coercion can be performed on empty array expressions
o Add support for arrays of domains
http://archives.postgresql.org/pgsql-patches/2007-05/msg00114.php
o Allow single-byte header storage for array elements
* Binary Data
o Improve vacuum of large objects, like contrib/vacuumlo?
o Add security checking for large objects
o Auto-delete large objects when referencing row is deleted
contrib/lo offers this functionality.
o Allow read/write into TOAST values like large objects
This requires the TOAST column to be stored EXTERNAL.
o Add API for 64-bit large object access
http://archives.postgresql.org/pgsql-hackers/2005-09/msg00781.php
* MONEY data type
* Add locale-aware MONEY type, and support multiple currencies
http://archives.postgresql.org/pgsql-general/2005-08/msg01432.php
http://archives.postgresql.org/pgsql-hackers/2007-03/msg01181.php
* MONEY dumps in a locale-specific format making it difficult to
restore to a system with a different locale
* Allow MONEY to be easily cast to/from other numeric data types
Functions
=========
* Allow INET subnet tests using non-constants to be indexed
* Allow to_date() and to_timestamp() accept localized month names
* Fix to_date()-related functions to consistently issue errors
http://archives.postgresql.org/pgsql-hackers/2007-02/msg00915.php
* Add missing parameter handling in to_char()
http://archives.postgresql.org/pgsql-hackers/2005-12/msg00948.php
* Allow substring/replace() to get/set bit values
* Allow to_char() on interval values to accumulate the highest unit
requested
Some special format flag would be required to request such
accumulation. Such functionality could also be added to EXTRACT.
Prevent accumulation that crosses the month/day boundary because of
the uneven number of days in a month.
o to_char(INTERVAL '1 hour 5 minutes', 'MI') => 65
o to_char(INTERVAL '43 hours 20 minutes', 'MI' ) => 2600
o to_char(INTERVAL '43 hours 20 minutes', 'WK:DD:HR:MI') => 0:1:19:20
o to_char(INTERVAL '3 years 5 months','MM') => 41
* Implement inlining of set-returning functions defined in SQL
* Allow SQL-language functions to return results from RETURNING queries
http://archives.postgresql.org/pgsql-hackers/2006-10/msg00665.php
* Allow SQL-language functions to reference parameters by parameter name
Currently SQL-language functions can only refer to dollar parameters,
e.g. $1
* Add SPI_gettypmod() to return the typemod for a TupleDesc
* Enforce typmod for function inputs, function results and parameters for
spi_prepare'd statements called from PLs
http://archives.postgresql.org/pgsql-hackers/2007-01/msg01403.php
* Allow holdable cursors in SPI
* Tighten function permission checks
http://archives.postgresql.org/pgsql-hackers/2006-12/msg00568.php
* Fix IS OF so it matches the ISO specification, and add documentation
http://archives.postgresql.org/pgsql-patches/2003-08/msg00060.php
http://archives.postgresql.org/pgsql-hackers/2007-02/msg00060.php
* Add missing operators for geometric data types
Some geometric types do not have the full suite of geometric operators,
e.g. box @> point
* Implement Boyer-Moore searching in strpos()
http://archives.postgresql.org/pgsql-patches/2007-08/msg00012.php
* Prevent malicious functions from being executed with the permissions
of unsuspecting users
Index functions are safe, so VACUUM and ANALYZE are safe too.
Triggers, CHECK and DEFAULT expressions, and rules are still vulnerable.
http://archives.postgresql.org/pgsql-hackers/2008-01/msg00268.php
* Reduce memory usage of aggregates in set returning functions
http://archives.postgresql.org/pgsql-performance/2008-01/msg00031.php
* Add temporal versions of generate_series()
http://archives.postgresql.org/pgsql-hackers/2007-04/msg01180.php
* Add array_accum() and array_to_set() functions for arrays
The standards specify array_agg() and UNNEST.
http://archives.postgresql.org/pgsql-hackers/2007-08/msg00464.php
* Fix /contrib/ltree operator
http://archives.postgresql.org/pgsql-bugs/2007-11/msg00044.php
* Fix inconsistent precedence of =, >, and < compared to <>, >=, and <=
http://archives.postgresql.org/pgsql-bugs/2007-12/msg00145.php
Multi-Language Support
======================
* Add NCHAR (as distinguished from ordinary varchar),
* Allow locale to be set at database creation
Currently locale can only be set during initdb. No global tables have
locale-aware columns. However, the database template used during
database creation might have locale-aware indexes. The indexes would
need to be reindexed to match the new locale.
* Allow encoding on a per-column basis optionally using the ICU library:
Right now only one encoding is allowed per database. [locale]
http://archives.postgresql.org/pgsql-hackers/2005-03/msg00932.php
http://archives.postgresql.org/pgsql-patches/2005-08/msg00309.php
http://archives.postgresql.org/pgsql-patches/2006-03/msg00233.php
http://archives.postgresql.org/pgsql-hackers/2006-09/msg00662.php
* Add CREATE COLLATE? [locale]
* Support multiple simultaneous character sets, per SQL92
* Improve UTF8 combined character handling?
* Add octet_length_server() and octet_length_client()
* Make octet_length_client() the same as octet_length()?
* Fix problems with wrong runtime encoding conversion for NLS message files
* Add URL to more complete multi-byte regression tests
http://archives.postgresql.org/pgsql-hackers/2005-07/msg00272.php
* Fix ILIKE and regular expressions to handle case insensitivity
properly in multibyte encodings
http://archives.postgresql.org/pgsql-bugs/2005-10/msg00001.php
http://archives.postgresql.org/pgsql-patches/2005-11/msg00173.php
* Set client encoding based on the client operating system encoding
Currently client_encoding is set in postgresql.conf, which
defaults to the server encoding.
http://archives.postgresql.org/pgsql-hackers/2006-08/msg01696.php
* Change memory allocation for multi-byte functions so memory is
allocated inside conversion functions
Currently we preallocate memory based on worst-case usage.
Views / Rules
=============
* Automatically create rules on views so they are updateable, per SQL99
We can only auto-create rules for simple views. For more complex
cases users will still have to write rules manually.
http://archives.postgresql.org/pgsql-hackers/2006-03/msg00586.php
http://archives.postgresql.org/pgsql-patches/2006-08/msg00255.php
* Add the functionality for WITH CHECK OPTION clause of CREATE VIEW
* Allow NOTIFY in rules involving conditionals
* Allow VIEW/RULE recompilation when the underlying tables change
Another issue is whether underlying table changes should be reflected
in the view, e.g. should SELECT * show additional columns if they
are added after the view is created.
* Make it possible to use RETURNING together with conditional DO INSTEAD
rules, such as for partitioning setups
http://archives.postgresql.org/pgsql-hackers/2007-09/msg00577.php
* Add the ability to automatically create materialized views
Right now materialized views require the user to create triggers on the
main table to keep the summary table current. SQL syntax should be able
to manager the triggers and summary table automatically. A more
sophisticated implementation would automatically retrieve from the
summary table when the main table is referenced, if possible.
SQL Commands
============
* Add CORRESPONDING BY to UNION/INTERSECT/EXCEPT
* Add ROLLUP, CUBE, GROUPING SETS options to GROUP BY
* %Allow SET CONSTRAINTS to be qualified by schema/table name
* %Add a separate TRUNCATE permission
Currently only the owner can TRUNCATE a table because triggers are not
called, and the table is locked in exclusive mode.
* Allow PREPARE of cursors
* Allow finer control over the caching of prepared query plans
Currently queries prepared via the libpq API are planned on first
execute using the supplied parameters --- allow SQL PREPARE to do the
same. Also, allow control over replanning prepared queries either
manually or automatically when statistics for execute parameters
differ dramatically from those used during planning.
* Improve logging of prepared transactions recovered during startup
http://archives.postgresql.org/pgsql-hackers/2006-11/msg00092.php
* Allow LISTEN/NOTIFY to store info in memory rather than tables?
Currently LISTEN/NOTIFY information is stored in pg_listener. Storing
such information in memory would improve performance.
* Add optional textual message to NOTIFY
This would allow an informational message to be added to the notify
message, perhaps indicating the row modified or other custom
information.
* Allow multiple identical NOTIFY events to always be communicated to the
client, rather than sent as a single notification to the listener
http://archives.postgresql.org/pgsql-general/2008-01/msg00057.php
* Add a GUC variable to warn about non-standard SQL usage in queries
* Add SQL-standard MERGE command, typically used to merge two tables
[merge]
This is similar to UPDATE, then for unmatched rows, INSERT.
Whether concurrent access allows modifications which could cause
row loss is implementation independent.
* Add REPLACE or UPSERT command that does UPDATE, or on failure, INSERT
[merge]
To implement this cleanly requires that the table have a unique index
so duplicate checking can be easily performed. It is possible to
do it without a unique index if we require the user to LOCK the table
before the MERGE.
http://archives.postgresql.org/pgsql-hackers/2005-11/msg00501.php
http://archives.postgresql.org/pgsql-hackers/2005-11/msg00536.php
* Add NOVICE output level for helpful messages like automatic sequence/index
creation
* Add GUC to issue notice about statements that use unjoined tables
* Allow EXPLAIN to identify tables that were skipped because of
constraint_exclusion
* Allow EXPLAIN output to be more easily processed by scripts, perhaps XML
* Enable standard_conforming_strings
* Make standard_conforming_strings the default in 8.5?
When this is done, backslash-quote should be prohibited in non-E''
strings because of possible confusion over how such strings treat
backslashes. Basically, '' is always safe for a literal single
quote, while \' might or might not be based on the backslash
handling rules.
* Simplify dropping roles that have objects in several databases
* Allow COMMENT ON to accept an expression rather than just a string
* Allow the count returned by SELECT, etc to be represented as an int64
to allow a higher range of values
* Add SQL99 WITH clause to SELECT
* Add SQL:2003 WITH RECURSIVE (hierarchical) queries to SELECT
http://archives.postgresql.org/pgsql-hackers/2007-01/msg01375.php
http://archives.postgresql.org/pgsql-hackers/2008-02/msg00642.php
http://archives.postgresql.org/pgsql-patches/2007-03/msg00139.php
http://archives.postgresql.org/pgsql-hackers/2007-11/msg01334.php
* Add DEFAULT .. AS OWNER so permission checks are done as the table
owner
This would be useful for SERIAL nextval() calls and CHECK constraints.
* Allow DISTINCT to work in multiple-argument aggregate calls
* Add column to pg_stat_activity that shows the progress of long-running
commands like CREATE INDEX and VACUUM
* Implement SQL:2003 window functions
* Improve failure message when DROP DATABASE is used on a database that
has prepared transactions
* Allow INSERT/UPDATE ... RETURNING inside a SELECT 'FROM' clause
http://archives.postgresql.org/pgsql-general/2006-09/msg00803.php
http://archives.postgresql.org/pgsql-hackers/2006-10/msg00693.php
* Increase locking when DROPing objects so dependent objects cannot
get dropped while the DROP operation is happening
http://archives.postgresql.org/pgsql-hackers/2007-01/msg00937.php
* -Allow AS in "SELECT col AS label" to be optional in certain cases
* Allow INSERT ... DELETE ... RETURNING, namely allow the DELETE ...
RETURNING to supply values to the INSERT
http://archives.postgresql.org/pgsql-hackers/2008-02/thrd2.php#00979
* Add comments on system tables/columns using the information in
catalogs.sgml
Ideally the information would be pulled from the SGML file
automatically.
* CREATE
o Allow CREATE TABLE AS to determine column lengths for complex
expressions like SELECT col1 || col2
o Have WITH CONSTRAINTS also create constraint indexes
http://archives.postgresql.org/pgsql-patches/2007-04/msg00149.php
o Have CONSTRAINT cname NOT NULL record the contraint name
Right now pg_attribute.attnotnull records the NOT NULL status
of the column, but does not record the contraint name
* UPDATE
o Allow UPDATE tab SET ROW (col, ...) = (SELECT...)
http://archives.postgresql.org/pgsql-hackers/2006-07/msg01306.php
http://archives.postgresql.org/pgsql-hackers/2007-03/msg00865.php
http://archives.postgresql.org/pgsql-patches/2007-04/msg00315.php
http://archives.postgresql.org/pgsql-patches/2008-03/msg00237.php
o Research self-referential UPDATEs that see inconsistent row versions
in read-committed mode
http://archives.postgresql.org/pgsql-hackers/2007-05/msg00507.php
http://archives.postgresql.org/pgsql-hackers/2007-06/msg00016.php
o Allow GLOBAL temporary tables to exist as empty by default in
all sessions
http://archives.postgresql.org/pgsql-hackers/2007-07/msg00006.php
* ALTER
o Have ALTER TABLE RENAME rename SERIAL sequence names
http://archives.postgresql.org/pgsql-hackers/2008-03/msg00008.php
o Have ALTER SEQUENCE RENAME rename the sequence name stored
in the sequence table
http://archives.postgresql.org/pgsql-bugs/2007-09/msg00092.php
http://archives.postgresql.org/pgsql-bugs/2007-10/msg00007.php
http://archives.postgresql.org/pgsql-hackers/2008-03/msg00008.php
o Add ALTER DOMAIN to modify the underlying data type
o %Allow ALTER TABLE ... ALTER CONSTRAINT ... RENAME
http://archives.postgresql.org/pgsql-patches/2006-02/msg00168.php
o %Allow ALTER TABLE to change constraint deferrability and actions
o Add missing object types for ALTER ... SET SCHEMA
o Allow ALTER TABLESPACE to move to different directories
o Allow databases to be moved to different tablespaces
o Allow moving system tables to other tablespaces, where possible
Currently non-global system tables must be in the default database
tablespace. Global system tables can never be moved.
o Prevent parent tables from altering or dropping constraints
like CHECK that are inherited by child tables unless CASCADE
is used
o %Prevent child tables from altering or dropping constraints
like CHECK that were inherited from the parent table
o Have ALTER INDEX update the name of a constraint using that index
o Add ALTER TABLE RENAME CONSTRAINT, update index name also
o Allow column display reordering by recording a display,
storage, and permanent id for every column?
http://archives.postgresql.org/pgsql-hackers/2006-12/msg00782.php
* CLUSTER
o Automatically maintain clustering on a table
This might require some background daemon to maintain clustering
during periods of low usage. It might also require tables to be only
partially filled for easier reorganization. Another idea would
be to create a merged heap/index data file so an index lookup would
automatically access the heap data too. A third idea would be to
store heap rows in hashed groups, perhaps using a user-supplied
hash function.
http://archives.postgresql.org/pgsql-performance/2004-08/msg00349.php
o %Add default clustering to system tables
To do this, determine the ideal cluster index for each system
table and set the cluster setting during initdb.
o %Add VERBOSE option to report tables as they are processed,
like VACUUM VERBOSE
* COPY
o Allow COPY to report error lines and continue
This requires the use of a savepoint before each COPY line is
processed, with ROLLBACK on COPY failure.
http://archives.postgresql.org/pgsql-hackers/2007-12/msg00572.php
o Allow COPY on a newly-created table to skip WAL logging
On crash recovery, the table involved in the COPY would
be removed or have its heap and index files truncated. One
issue is that no other backend should be able to add to
the table at the same time, which is something that is
currently allowed. This currently is done if the table is
created inside the same transaction block as the COPY because
no other backends can see the table.
o Consider using a ring buffer for COPY FROM
http://archives.postgresql.org/pgsql-patches/2008-02/msg00140.php
http://archives.postgresql.org/pgsql-hackers/2008-02/msg01080.php
o Allow COPY FROM to create index entries in bulk
http://archives.postgresql.org/pgsql-hackers/2008-02/msg00811.php
o Allow COPY in CSV mode to control whether a quoted zero-length
string is treated as NULL
Currently this is always treated as a zero-length string,
which generates an error when loading into an integer column
http://archives.postgresql.org/pgsql-hackers/2007-07/msg00905.php
* GRANT/REVOKE
o Allow column-level privileges
o %Allow GRANT/REVOKE permissions to be applied to all schema objects
with one command
The proposed syntax is:
GRANT SELECT ON ALL TABLES IN public TO phpuser;
GRANT SELECT ON NEW TABLES IN public TO phpuser;
o Allow GRANT/REVOKE permissions to be inherited by objects based on
schema permissions
o Allow SERIAL sequences to inherit permissions from the base table?
* CURSOR
o Prevent DROP TABLE from dropping a row referenced by its own open
cursor?
* INSERT
o Allow INSERT/UPDATE of the system-generated oid value for a row
o In rules, allow VALUES() to contain a mixture of 'old' and 'new'
references
* SHOW/SET
o Add SET PERFORMANCE_TIPS option to suggest INDEX, VACUUM, VACUUM
ANALYZE, and CLUSTER
Referential Integrity
=====================
* Add MATCH PARTIAL referential integrity
* Change foreign key constraint for array -> element to mean element
in array?
* Fix problem when cascading referential triggers make changes on
cascaded tables, seeing the tables in an intermediate state
http://archives.postgresql.org/pgsql-hackers/2005-09/msg00174.php
http://archives.postgresql.org/pgsql-hackers/2005-09/msg00174.php
* Allow DEFERRABLE and end-of-statement UNIQUE constraints?
This would allow UPDATE tab SET col = col + 1 to work if col has
a unique index. Currently, uniqueness checks are done while the
command is being executed, rather than at the end of the statement
or transaction.
http://people.planetpostgresql.org/greg/index.php?/archives/2006/06/10.html
http://archives.postgresql.org/pgsql-hackers/2006-09/msg01458.php
* Optimize referential integrity checks
http://archives.postgresql.org/pgsql-performance/2005-10/msg00458.php
http://archives.postgresql.org/pgsql-hackers/2007-04/msg00744.php
Server-Side Languages
=====================
* PL/pgSQL
o Fix RENAME to work on variables other than OLD/NEW
http://archives.postgresql.org/pgsql-hackers/2002-03/msg00591.php
http://archives.postgresql.org/pgsql-hackers/2007-01/msg01615.php
http://archives.postgresql.org/pgsql-hackers/2007-01/msg01587.php
o Allow function parameters to be passed by name,
get_employee_salary(12345 AS emp_id, 2001 AS tax_year)
o Allow handling of %TYPE arrays, e.g. tab.col%TYPE[]
o Allow listing of record column names, and access to
record columns via variables, e.g. columns := r.(*),
tval2 := r.(colname)
http://archives.postgresql.org/pgsql-patches/2005-07/msg00458.php
http://archives.postgresql.org/pgsql-patches/2006-05/msg00302.php
http://archives.postgresql.org/pgsql-patches/2006-06/msg00031.php
o Add support for SCROLL cursors
o Add support for WITH HOLD cursors
o Allow row and record variables to be set to NULL constants,
and allow NULL tests on such variables
Because a row is not scalar, do not allow assignment
from NULL-valued scalars.
http://archives.postgresql.org/pgsql-hackers/2006-10/msg00070.php
o Review handling of MOVE and FETCH
http://archives.postgresql.org/pgsql-patches/2007-04/msg00527.php
o Improve logic of determining if an identifier is a a
variable or column name
http://archives.postgresql.org/pgsql-hackers/2007-07/msg00436.php
* Other
o Add table function support to pltcl, plpythonu
o Add support for polymorphic arguments and return types to
languages other than PL/PgSQL
o Add capability to create and call PROCEDURES
o Add support for OUT and INOUT parameters to languages other
than PL/PgSQL
o Add PL/PythonU tracebacks
http://archives.postgresql.org/pgsql-patches/2006-02/msg00288.php
o Allow data to be passed in native language formats, rather
than only text
http://archives.postgresql.org/pgsql-hackers/2007-05/msg00289.php
Clients
=======
* Have pg_ctl look at PGHOST in case it is a socket directory?
* Allow pg_ctl to work properly with configuration files located outside
the PGDATA directory
pg_ctl can not read the pid file because it isn't located in the
config directory but in the PGDATA directory. The solution is to
allow pg_ctl to read and understand postgresql.conf to find the
data_directory value.
* Add a function like pg_get_indexdef() that report more detailed index
information
http://archives.postgresql.org/pgsql-bugs/2007-12/msg00166.php
* Prefix command-line utilities like createuser with 'pg_'
http://archives.postgresql.org/pgsql-hackers/2007-06/msg00025.php
* psql
o Have psql show current values for a sequence
o 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.
o Fix psql's \d commands more consistent
http://archives.postgresql.org/pgsql-hackers/2004-11/msg00014.php
http://archives.postgresql.org/pgsql-hackers/2004-11/msg00014.php
o Consistently display privilege information for all objects in psql
o Add auto-expanded mode so expanded output is used if the row
length is wider than the screen width.
Consider using auto-expanded mode for backslash commands like \df+.
o Prevent tab completion of SET TRANSACTION from querying the
database and therefore preventing the transaction isolation
level from being set.
Currently SET <tab> causes a database lookup to check all
supported session variables. This query causes problems
because setting the transaction isolation level must be the
first statement of a transaction.
o Add a \set variable to control whether \s displays line numbers
Another option is to add \# which lists line numbers, and
allows command execution.
http://archives.postgresql.org/pgsql-hackers/2006-12/msg00255.php
o Prevent escape string warnings when object names have
backslashes
http://archives.postgresql.org/pgsql-hackers/2008-01/msg00227.php
o Have \d show foreign keys that reference a table's primary key
http://archives.postgresql.org/pgsql-hackers/2007-04/msg00424.php
o Have \d show child tables that inherit from the specified parent
o Have \l+ show database size, if permissions allow
Ideally it will not generate an error for invalid permissions
o Include the symbolic SQLSTATE name in verbose error reports
http://archives.postgresql.org/pgsql-general/2007-09/msg00438.php
* pg_dump / pg_restore
o %Add dumping of comments on index columns and composite type columns
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?
o Allow selection of individual object(s) of all types, not just
tables
o In a selective dump, allow dumping of an object and all its
dependencies
o Add options like pg_restore -l and -L to pg_dump
o Stop dumping CASCADE on DROP TYPE commands in clean mode
o Allow pg_dump --clean to drop roles that own objects or have
privileges
o Change pg_dump so that a comment on the dumped database is
applied to the loaded database, even if the database has a
different name. This will require new backend syntax, perhaps
COMMENT ON CURRENT DATABASE.
o Remove unnecessary function pointer abstractions in pg_dump source
code
o Allow pg_dump to utilize multiple CPUs and I/O channels by dumping
multiple objects simultaneously
The difficulty with this is getting multiple dump processes to
produce a single dump output file. It also would require
several sessions to share the same snapshot.
http://archives.postgresql.org/pgsql-hackers/2008-02/msg00205.php
o Allow pg_restore to utilize multiple CPUs and I/O channels by
restoring multiple objects simultaneously
This might require a pg_restore flag to indicate how many
simultaneous operations should be performed. Only pg_dump's
-Fc format has the necessary dependency information.
http://archives.postgresql.org/pgsql-hackers/2008-02/msg00963.php
o To better utilize resources, allow pg_restore to check foreign
keys simultaneously, where possible
o Allow pg_restore to create all indexes of a table
concurrently, via a single heap scan
This requires a pg_dump -Fc file because that format contains
the required dependency information.
http://archives.postgresql.org/pgsql-general/2007-05/msg01274.php
o Allow pg_restore to load different parts of the COPY data
simultaneously
o Prevent pg_dump/pg_restore from being affected by
statement_timeout
Using psql to restore a pg_dump dump is also affected.
o Remove pre-7.3 pg_dump code that assumes pg_depend does not exit
* 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
o Add internationalized message strings
o Implement COPY FROM STDIN
* libpq
o Add PQescapeIdentifierConn()
o Prevent PQfnumber() from lowercasing unquoted the column name
PQfnumber() should never have been doing lowercasing, but
historically it has so we need a way to prevent it
o Allow statement results to be automatically batched to the client
Currently all statement results are transferred to the libpq
client before libpq makes the results available to the
application. This feature would allow the application to make
use of the first result rows while the rest are transferred, or
held on the server waiting for them to be requested by libpq.
One complexity is that a statement like SELECT 1/col could error
out mid-way through the result set.
o Consider disallowing multiple queries in PQexec() as an
additional barrier to SQL injection attacks
http://archives.postgresql.org/pgsql-hackers/2007-01/msg00184.php
o Add PQexecf() that allows complex parameter substitution
http://archives.postgresql.org/pgsql-hackers/2007-03/msg01803.php
o Add SQLSTATE severity to PGconn return status
http://archives.postgresql.org/pgsql-interfaces/2007-11/msg00015.php
Triggers
========
* 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.
* Allow triggers to be disabled in only the current session.
This is currently possible by starting a multi-statement transaction,
modifying the system tables, performing the desired SQL, restoring the
system tables, and committing the transaction. ALTER TABLE ...
TRIGGER requires a table lock so it is not ideal for this usage.
* 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
http://archives.postgresql.org/pgsql-patches/2005-07/msg00107.php
* 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.
* Tighten trigger permission checks
http://archives.postgresql.org/pgsql-hackers/2006-12/msg00564.php
* Allow BEFORE INSERT triggers on views
http://archives.postgresql.org/pgsql-general/2007-02/msg01466.php
* Add ability to trigger on TRUNCATE
http://archives.postgresql.org/pgsql-sql/2008-01/msg00050.php
Indexes
=======
* Add UNIQUE capability to non-btree indexes
* Prevent index uniqueness checks when UPDATE does not modify the column
Uniqueness (index) checks are done when updating a column even if the
column is not modified by the UPDATE.
* Allow the creation of on-disk bitmap indexes which can be quickly
combined with other bitmap indexes
Such indexes could be more compact if there are only a few distinct values.
Such indexes can also be compressed. Keeping such indexes updated can be
costly.
http://archives.postgresql.org/pgsql-patches/2005-07/msg00512.php
http://archives.postgresql.org/pgsql-hackers/2006-12/msg01107.php
* Allow accurate statistics to be collected on indexes with more than
one column or expression indexes, perhaps using per-index statistics
http://archives.postgresql.org/pgsql-performance/2006-10/msg00222.php
http://archives.postgresql.org/pgsql-hackers/2007-03/msg01131.php
* Consider increasing the number of default statistics target, and
reduce statistics target overhead
Also consider having a larger statistics target for indexed columns
and expression indexes
http://archives.postgresql.org/pgsql-general/2007-05/msg01228.php
http://archives.postgresql.org/pgsql-general/2007-06/msg00542.php
http://archives.postgresql.org/pgsql-hackers/2008-01/msg01066.php
* Consider compressing indexes by storing key values duplicated in
several rows as a single index entry
http://archives.postgresql.org/pgsql-hackers/2006-12/msg00341.php
http://archives.postgresql.org/pgsql-hackers/2007-02/msg01264.php
http://archives.postgresql.org/pgsql-hackers/2007-03/msg00465.php
http://archives.postgresql.org/pgsql-patches/2007-03/msg00163.php
* Add REINDEX CONCURRENTLY, like CREATE INDEX CONCURRENTLY
This is difficult because you must upgrade to an exclusive table lock
to replace the existing index file. CREATE INDEX CONCURRENTLY does not
have this complication. This would allow index compaction without
downtime.
http://archives.postgresql.org/pgsql-performance/2007-08/msg00289.php
* Allow multiple indexes to be created concurrently, ideally via a
single heap scan, and have pg_restore use it
* Inheritance
o Allow inherited tables to inherit indexes, UNIQUE constraints,
and primary/foreign keys
o Honor UNIQUE INDEX on base column in INSERTs/UPDATEs
on inherited table, e.g. INSERT INTO inherit_table
(unique_index_col) VALUES (dup) should fail
The main difficulty with this item is the problem of
creating an index that can span multiple tables.
o Allow SELECT ... FOR UPDATE on inherited tables
o Require all CHECK constraints to be inherited
http://archives.postgresql.org/pgsql-bugs/2007-04/msg00026.php
o Add checks to prevent a CREATE RULE views on inherited tables
http://archives.postgresql.org/pgsql-general/2008-02/msg01420.php
http://archives.postgresql.org/pgsql-general/2008-03/msg00077.php
* GIST
o Add more GIST index support for geometric data types
o Allow GIST indexes to create certain complex index types, like
digital trees (see Aoki)
* Hash
http://archives.postgresql.org/pgsql-hackers/2007-09/msg00051.php
o Pack hash index buckets onto disk pages more efficiently
Currently only one hash bucket can be stored on a page. Ideally
several hash buckets could be stored on a single page and greater
granularity used for the hash algorithm.
http://archives.postgresql.org/pgsql-hackers/2004-06/msg00168.php
o Consider sorting hash buckets so entries can be found using a
binary search, rather than a linear scan
o In hash indexes, consider storing the hash value with or instead
of the key itself
o Add WAL logging for crash recovery
o Allow multi-column hash indexes
o -During index creation, pre-sort the tuples to improve build speed
Fsync
=====
* Determine optimal fdatasync/fsync, O_SYNC/O_DSYNC options
Ideally this requires a separate test program that can be run
at initdb time or optionally later. Consider O_SYNC when
O_DIRECT exists.
* Add program to test if fsync has a delay compared to non-fsync
* Consider sorting writes during checkpoint
http://archives.postgresql.org/pgsql-hackers/2007-06/msg00541.php
Cache Usage
===========
* 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.
* Provide a way to calculate an "estimated COUNT(*)"
Perhaps by using the optimizer's cardinality estimates or random
sampling.
http://archives.postgresql.org/pgsql-hackers/2005-11/msg00943.php
* Allow data to be pulled directly from indexes
Currently indexes do not have enough 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 on 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.
Another idea is to maintain a bitmap of heap pages where all rows
are visible to all backends, and allow index lookups to reference
that bitmap to avoid heap lookups, perhaps the same bitmap we might
add someday to determine which heap pages need vacuuming. Frequently
accessed bitmaps would have to be stored in shared memory. One 8k
page of bitmaps could track 512MB of heap pages.
A third idea would be for a heap scan to check if all rows are visible
and if so set a per-table flag which can be checked by index scans.
Any change to the table would have to clear the flag. To detect
changes during the heap scan a counter could be set at the start and
checked at the end --- if it is the same, the table has not been
modified --- any table change would increment the counter.
* Consider automatic caching of statements at various levels:
o Parsed query tree
o Query execute plan
o Query results
* Consider increasing internal areas when shared buffers is increased
http://archives.postgresql.org/pgsql-hackers/2005-10/msg01419.php
* Consider decreasing the amount of memory used by PrivateRefCount
http://archives.postgresql.org/pgsql-hackers/2006-11/msg00797.php
http://archives.postgresql.org/pgsql-hackers/2007-01/msg00752.php
* Consider allowing higher priority queries to have referenced buffer
cache pages stay in memory longer
http://archives.postgresql.org/pgsql-hackers/2007-11/msg00562.php
Vacuum
======
* Improve speed with indexes
For large table adjustments during VACUUM FULL, it is faster to cluster
or reindex rather than update the index. Also, index updates can bloat
the index.
http://archives.postgresql.org/pgsql-hackers/2007-03/msg00024.php
http://archives.postgresql.org/pgsql-performance/2007-05/msg00296.php
http://archives.postgresql.org/pgsql-hackers/2007-08/msg00307.php
* Auto-fill the free space map by scanning the buffer cache or by
checking pages written by the background writer
http://archives.postgresql.org/pgsql-hackers/2006-02/msg01125.php
http://archives.postgresql.org/pgsql-hackers/2006-03/msg00011.php
* Create a bitmap of pages that need vacuuming
Instead of sequentially scanning the entire table, have the background
writer or some other process record pages that have expired rows, then
VACUUM can look at just those pages rather than the entire table. In
the event of a system crash, the bitmap would probably be invalidated.
One complexity is that index entries still have to be vacuumed, and
doing this without an index scan (by using the heap values to find the
index entry) might be slow and unreliable, especially for user-defined
index functions.
http://archives.postgresql.org/pgsql-hackers/2006-12/msg01188.php
http://archives.postgresql.org/pgsql-hackers/2007-01/msg00121.php
* Allow FSM to return free space toward the beginning of the heap file,
in hopes that empty pages at the end can be truncated by VACUUM
* Allow FSM page return free space based on table clustering, to assist
in maintaining clustering?
* Improve dead row detection during multi-statement transactions usage
http://archives.postgresql.org/pgsql-patches/2007-03/msg00358.php
* Consider a more compact data representation for dead tuples
http://archives.postgresql.org/pgsql-patches/2007-05/msg00143.php
* Auto-vacuum
o %Issue log message to suggest VACUUM FULL if a table is nearly
empty?
o Improve control of auto-vacuum
http://archives.postgresql.org/pgsql-hackers/2006-12/msg00876.php
o Prevent long-lived temporary tables from causing frozen-xid
advancement starvation
The problem is that autovacuum cannot vacuum them to set frozen xids;
only the session that created them can do that.
http://archives.postgresql.org/pgsql-general/2007-06/msg01645.php
o Store per-table autovacuum settings in pg_class.reloptions.
http://archives.postgresql.org/pgsql-hackers/2007-02/msg01440.php
http://archives.postgresql.org/pgsql-hackers/2008-01/msg00724.php
o Prevent autovacuum from running if an old transaction is still
running from the last vacuum
http://archives.postgresql.org/pgsql-hackers/2007-11/msg00899.php
Locking
=======
* Fix priority ordering of read and write light-weight locks (Neil)
http://archives.postgresql.org/pgsql-hackers/2004-11/msg00893.php
http://archives.postgresql.org/pgsql-hackers/2004-11/msg00905.php
* Fix problem when multiple subtransactions of the same outer transaction
hold different types of locks, and one subtransaction aborts
http://archives.postgresql.org/pgsql-hackers/2006-11/msg01011.php
http://archives.postgresql.org/pgsql-hackers/2006-12/msg00001.php
http://archives.postgresql.org/pgsql-hackers/2007-02/msg00435.php
http://archives.postgresql.org/pgsql-hackers/2007-05/msg00773.php
* Allow UPDATEs on only non-referential integrity columns not to conflict
with referential integrity locks
http://archives.postgresql.org/pgsql-hackers/2007-02/msg00073.php
* Add idle_in_transaction_timeout GUC so locks are not held for long
periods of time
* Improve deadlock detection when a page cleaning lock conflicts
with a shared buffer that is pinned
http://archives.postgresql.org/pgsql-bugs/2008-01/msg00138.php
http://archives.postgresql.org/pgsql-hackers/2008-01/msg00873.php
http://archives.postgresql.org/pgsql-committers/2008-01/msg00365.php
Startup Time Improvements
=========================
* Experiment with multi-threaded backend for backend creation [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. Also explore the idea of
a single session using multiple threads to execute a statement faster.
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
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.
o When off, write CRC to WAL and check file system blocks
on recovery
If CRC check fails during recovery, remember the page in case
a later CRC for that page properly matches.
o Write full pages during file system write and not when
the page is modified in the buffer cache
This allows most full page writes to happen in the background
writer. It might cause problems for applying WAL on recovery
into a partially-written page, but later the full page will be
replaced from WAL.
* Allow WAL traffic to be streamed to another server for stand-by
replication
* Reduce WAL traffic so only modified values are written rather than
entire rows
http://archives.postgresql.org/pgsql-hackers/2007-03/msg01589.php
* Allow WAL information to recover corrupted pg_controldata
http://archives.postgresql.org/pgsql-patches/2006-06/msg00025.php
* 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 WAL logging to be turned off for a table, but the table
might be dropped or truncated during crash recovery [walcontrol]
Allow tables to bypass WAL writes and just fsync() dirty pages on
commit. This should be implemented using ALTER TABLE, e.g. ALTER
TABLE PERSISTENCE [ DROP | TRUNCATE | DEFAULT ]. Tables using
non-default logging should not use referential integrity with
default-logging tables. A table without dirty buffers during a
crash could perhaps avoid the drop/truncate.
* Allow WAL logging to be turned off for a table, but the table would
avoid being truncated/dropped [walcontrol]
To do this, only a single writer can modify the table, and writes
must happen only on new pages so the new pages can be removed during
crash recovery. Readers can continue accessing the table. Such
tables probably cannot have indexes. One complexity is the handling
of indexes on TOAST tables.
* Speed WAL recovery by allowing more than one page to be prefetched
This should be done utilizing the same infrastructure used for
prefetching in general to avoid introducing complex error-prone code
in WAL replay.
http://archives.postgresql.org/pgsql-general/2007-12/msg00683.php
http://archives.postgresql.org/pgsql-hackers/2007-12/msg00497.php
http://archives.postgresql.org/pgsql-hackers/2008-02/msg01279.php
* Improve WAL concurrency by increasing lock granularity
http://archives.postgresql.org/pgsql-hackers/2008-02/msg00556.php
Optimizer / Executor
====================
* Improve selectivity functions for geometric operators
* 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 issue NOTICE messages when the estimated and
actual row counts differ by a specified percentage
* Consider using hash buckets to do DISTINCT, rather than sorting
This would be beneficial when there are few distinct values. This is
already used by GROUP BY.
* Log statements where the optimizer row estimates were dramatically
different from the number of rows actually found?
* Consider compressed annealing to search for query plans
This might replace GEQO, http://sixdemonbag.org/Djinni.
* Improve merge join performance by allowing mark/restore of
tuple sources
http://archives.postgresql.org/pgsql-hackers/2007-01/msg00096.php
* Consider using a hash for joining to a large IN (VALUES ...) list
http://archives.postgresql.org/pgsql-hackers/2007-05/msg00450.php
Background Writer
=================
* Consider having the background writer update the transaction status
hint bits before writing out the page
Implementing this requires the background writer to have access to system
catalogs and the transaction status log.
* Consider adding buffers the background writer finds reusable to the
free list
http://archives.postgresql.org/pgsql-hackers/2007-04/msg00781.php
* Automatically tune bgwriter_delay based on activity rather then using a
fixed interval
http://archives.postgresql.org/pgsql-hackers/2007-04/msg00781.php
* Consider wither increasing BM_MAX_USAGE_COUNT improves performance
http://archives.postgresql.org/pgsql-hackers/2007-06/msg01007.php
* Test to see if calling PreallocXlogFiles() from the background writer
will help with WAL segment creation latency
http://archives.postgresql.org/pgsql-patches/2007-06/msg00340.php
Miscellaneous Performance
=========================
* 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.
http://archives.postgresql.org/pgsql-hackers/2006-10/msg00820.php
http://archives.postgresql.org/pgsql-performance/2007-09/msg00255.php
http://archives.postgresql.org/pgsql-hackers/2007-12/msg00027.php
* 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
* Consider ways of storing rows more compactly on disk
o Reduce the row header size?
o Consider reducing on-disk varlena length from four bytes to
two because a heap row cannot be more than 64k in length
* Consider increasing NUM_CLOG_BUFFERS
http://archives.postgresql.org/pgsql-hackers/2007-08/msg00030.php
http://archives.postgresql.org/pgsql-performance/2007-08/msg00024.php
* Allow user configuration of TOAST thresholds
http://archives.postgresql.org/pgsql-hackers/2007-02/msg00213.php
http://archives.postgresql.org/pgsql-hackers/2007-08/msg00082.php
* Allow configuration of backend priorities via the operating system
Though backend priorities make priority inversion during lock
waits possible, research shows that this is not a huge problem.
http://archives.postgresql.org/pgsql-general/2007-02/msg00493.php
* Experiment with multi-threaded backend better I/O utilization
This would allow a single query to make use of multiple I/O channels
simultaneously. One idea is to create a background reader that can
pre-fetch sequential and index scan pages needed by other backends.
This could be expanded to allow concurrent reads from multiple devices
in a partitioned table.
* Experiment with multi-threaded backend better CPU utilization
This would allow several CPUs to be used for a single query, such as
for sorting or query execution.
* Consider increasing the minimum allowed number of shared buffers
http://archives.postgresql.org/pgsql-bugs/2008-02/msg00157.php
* Expire published xmin for read-only and idle transactions
http://archives.postgresql.org/pgsql-hackers/2007-09/msg00343.php
* Consider if CommandCounterIncrement() can avoid its
AcceptInvalidationMessages() call
http://archives.postgresql.org/pgsql-committers/2007-11/msg00585.php
* Improve performance of shared invalidation queue for multiple CPUs
http://archives.postgresql.org/pgsql-performance/2008-01/msg00023.php
* Consider Cartesian joins when both relations are needed to form an
indexscan qualification for a third relation
http://archives.postgresql.org/pgsql-performance/2007-12/msg00090.php
* Consider not storing a NULL bitmap on disk if all the NULLs are
trailing
http://archives.postgresql.org/pgsql-hackers/2007-12/msg00624.php
http://archives.postgresql.org/pgsql-patches/2007-12/msg00109.php
* Avoid tuple some tuple copying in sort routines
http://archives.postgresql.org/pgsql-hackers/2008-02/msg01206.php
Source Code
===========
* Add use of 'const' for variables in source tree
* Move some things from contrib into main tree
* %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
* Acquire lock on a relation before building a relcache entry for it
* Allow cross-compiling by generating the zic database on the target system
* Improve NLS maintenance of libpgport messages linked onto applications
* Clean up casting in contrib/isn
http://archives.postgresql.org/pgsql-hackers/2006-11/msg00245.php
* Use UTF8 encoding for NLS messages so all server encodings can
read them properly
* Update Bonjour to work with newer cross-platform SDK
http://archives.postgresql.org/pgsql-hackers/2006-09/msg02238.php
http://archives.postgresql.org/pgsql-patches/2006-10/msg00048.php
* Consider detoasting keys before sorting
* Consider GnuTLS if OpenSSL license becomes a problem
http://archives.postgresql.org/pgsql-patches/2006-05/msg00040.php
http://archives.postgresql.org/pgsql-hackers/2006-12/msg01213.php
* Consider changing documentation format from SGML to XML
http://archives.postgresql.org/pgsql-docs/2006-12/msg00152.php
* Consider making NAMEDATALEN more configurable in future releases
* Update our code to handle 64-bit timezone files to match the zic
source code, which now uses them
* Have configure choose integer datetimes by default
http://archives.postgresql.org/pgsql-patches/2007-05/msg00046.php
* Support scoped IPv6 addresses
http://archives.postgresql.org/pgsql-bugs/2007-05/msg00111.php
* Consider allowing 64-bit integers and floats to be passed by value on
64-bit platforms
Also change 32-bit floats (float4) to be passed by value at the same
time.
* Research use of signals and sleep wake ups
http://archives.postgresql.org/pgsql-hackers/2007-07/msg00003.php
* Add automated check for invalid C++ source code constructs
http://archives.postgresql.org/pgsql-patches/2007-07/msg00056.php
* Consider simplifying how memory context resets handle child contexts
http://archives.postgresql.org/pgsql-patches/2007-08/msg00067.php
* Remove use of MAKE_PTR and MAKE_OFFSET macros
http://archives.postgresql.org/pgsql-general/2007-08/msg01510.php
* Convert single quotes to apostrophes in the PDF documentation
http://archives.postgresql.org/pgsql-docs/2007-12/msg00059.php
* 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 Fix problem with shared memory on the Win32 Terminal Server
o Diagnose problem where shared memory can sometimes not be
attached by postmaster children
http://archives.postgresql.org/pgsql-general/2007-08/msg01377.php
o Improve signal handling
http://archives.postgresql.org/pgsql-patches/2005-06/msg00027.php
o Convert MSVC build system to remove most batch files
http://archives.postgresql.org/pgsql-hackers/2007-08/msg00961.php
o Prevent SSL from sending network packets to avoid interference
with Win32 signal emulation
http://archives.postgresql.org/pgsql-hackers/2007-12/msg00455.php
o Support pgxs
o Fix MSVC NLS support, like for to_char()
http://archives.postgresql.org/pgsql-hackers/2008-02/msg00485.php
http://archives.postgresql.org/pgsql-patches/2008-02/msg00038.php
* 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 statement protocol
Exotic Features
===============
* Add pre-parsing phase that converts non-ISO 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
* Add features of Oracle-style packages (Pavel)
A package would be a schema with session-local variables,
public/private functions, and initialization functions. It
is also possible to implement these capabilities
in any schema and not use a separate "packages"
syntax at all.
http://archives.postgresql.org/pgsql-hackers/2006-08/msg00384.php
* Consider allowing control of upper/lower case folding of unquoted
identifiers
http://archives.postgresql.org/pgsql-hackers/2004-04/msg00818.php
http://archives.postgresql.org/pgsql-hackers/2006-10/msg01527.php
* Add autonomous transactions
http://archives.postgresql.org/pgsql-hackers/2008-01/msg00893.php
Features We Do _Not_ Want
=========================
* All backends running as threads in a single process (not wanted)
This eliminates the process protection we get from the current setup.
Thread creation is usually the same overhead as process creation on
modern systems, so it seems unwise to use a pure threaded model.
* Optimizer hints (not wanted)
Optimizer hints are used to work around problems in the optimizer. We
would rather have the problems reported and fixed.
http://archives.postgresql.org/pgsql-hackers/2006-08/msg00506.php
http://archives.postgresql.org/pgsql-hackers/2006-10/msg00517.php
http://archives.postgresql.org/pgsql-hackers/2006-10/msg00663.php
Because we support postfix operators, it isn't possible to make AS
optional and continue to use bison.
http://archives.postgresql.org/pgsql-hackers/2003-04/msg00436.php
http://archives.postgresql.org/pgsql-sql/2006-08/msg00164.php
* Embedded server (not wanted)
While PostgreSQL clients runs fine in limited-resource environments, the
server requires multiple processes and a stable pool of resources to
run reliabily and efficiently. Stripping down the PostgreSQL server
to run in the same process address space as the client application
would add too much complexity and failure cases.
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