PostgreSQL TODO List

====================

Current maintainer:Bruce Momjian (bruce@momjian.us)

Last updated:Wed Aug 1 19:13:20 EDT 2007

Last updated:Mon Aug27 22:56:24 EDT 2007

The most recent version of this document can be viewed at

http://www.postgresql.org/docs/faqs.TODO.html.

Administration

==============

* Allow major upgrades without dump/reload, perhaps using pg_upgrade

* Allow major upgrades without dump/reload, perhaps using pg_upgrade

[pg_upgrade]

* 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

* Allow administrators to safely terminate individual sessions either

via an SQL function or SIGTERM

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

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

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

Monitoring

==========

* Allow server log information to be output as INSERT statements

This would allow server log information to be easily loaded into

a database for analysis.

* -Allow server log information to be output as CSV format

* -Add ability to monitor the use of temporary sort files

* Dates and Times

o Allow infinite dates and intervals just like infinite timestamps

o Merge hardwired timezone names with the TZ database; allow either

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

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

o Add a GUC variable to allow output of interval values in ISO8601

format

o Have timestamp subtraction not call justify_hours()?

requested

Some special format flag would be required to request such

accumulation. Such functionality could also be added to EXTRACT.

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', '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

creation

* -Add RESET SESSION command to reset all session state

* Add GUC to issue notice about statements that use unjoined tables

* Allow EXPLAIN to identify tables that were skipped because of

* 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

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

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.

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

o Add support for OUT and INOUT parameters to languages other

than PL/PgSQL

o Add PL/PythonU tracebacks

than toggle

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.

length is wider than the screen width.

Consider using auto-expanded mode for backslash commands like \df+.

o Add PQescapeIdentifierConn()

o Prevent PQfnumber() from lowercasing unquoted the column name

PQfnumber() should never have been doing lowercasing, but

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

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.

* 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.

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

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

http://archives.postgresql.org/pgsql-hackers/2006-06/msg01305.php

http://archives.postgresql.org/pgsql-hackers/2006-06/msg01534.php

* Reuse index tuples that point to heap tuples that are not visible to

* Reuse index tuples that point to heap tuples that are not visible to

anyone?

* Improve dead row detection during multi-statement transactions usage

http://archives.postgresql.org/pgsql-patches/2007-03/msg00358.php

* Reduce XID consumption of read-only queries

http://archives.postgresql.org/pgsql-hackers/2007-08/msg00516.php

* Auto-vacuum

o Use free-space map information to guide refilling

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

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

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

crash recovery. Readers can continue accessing the table. Such

tables probably cannot have indexes. One complexity is the handling

of indexes on TOAST tables.

This might replace GEQO, http://sixdemonbag.org/Djinni.

* Improve merge join performance by allowing mark/restore of

* Improve merge join performance by allowing mark/restore of

tuple sources

http://archives.postgresql.org/pgsql-hackers/2007-01/msg00096.php

o -Support a smaller header for short variable-length fields

o Reduce the row header size?

o Consider reducing on-disk varlena length from four bytes to

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

* -Move NAMEDATALEN from postgres_ext.h to pg_config_manual.h

* Consider making NAMEDATALEN more configurable in future releases

* Update our code to handle 64-bit timezone files to match the zic

* 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

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

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.