Bracketed items "[]" have more detail.
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
-Last updated: Sat Jul 31 02:13:51 EDT 2004
+Last updated: Sun Aug 1 01:15:12 EDT 2004
The most recent version of this document can be viewed at the PostgreSQL web site, http://www.PostgreSQL.org.
+Remove items before beta?
Urgent
======
Administration
==============
-* Incremental backups
+* -Incremental backups
* Remove behavior of postmaster -o after making postmaster/postgres
flags unique
* -Allow configuration files to be specified in a different directory
* -Allow logging of only data definition(DDL), or DDL and modification statements
* -Allow log lines to include session-level information, like database and user
* 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.
+
* Prevent default re-use of sysids for dropped users and groups
+
+ Currently, if a user is removed while he still owns objects, a new
+ user given might be given their user id and inherit the
+ previous users objects.
+
* Prevent dropping user that still owns objects, or auto-drop the objects
-* Allow pooled connections to query prepared queries
-* Allow pooled connections to close all open WITH HOLD cursors
+* Allow pooled connections to list all prepared queries
+
+ This would allow an application inheriting a pooled connection to know
+ the queries prepared in the current session.
+
* Allow major upgrades without dump/reload, perhaps using pg_upgrade
-* Have SHOW ALL and pg_settings show descriptions for server-side variables(Joe)
-* Allow external interfaces to extend the GUC variable set
-* Allow GRANT/REVOKE permissions to be given to all schema objects with one command
+* Have SHOW ALL and pg_settings show descriptions for server-side variables
+* -Allow external interfaces to extend the GUC variable set
+* Allow GRANT/REVOKE permissions to be given to all schema objects with one
+ command
* Remove unreferenced table files created by transactions that were
in-progress when the server terminated abruptly
* 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.
+
* Allow database recovery where tablespaces can't be created
-* Add include functionality to postgresql.conf
-* Allow changing of already-created database and schema tablespaces
-* Allow moving system tables to other tablespaces, where possible
+
+ When a pg_dump is restored, all tablespaces will attempt to be created
+ in their original locations. If this fails, the user must be able to
+ adjust the restore process.
+
+* Add "include file" functionality in postgresql.conf
* Add session start time and last statement time to pg_stat_activity
-* Allow server logs to be read using SQL commands
-* Allow server configuration parameters to be modified remotetly
+* Allow server logs to be remotely read using SQL commands
+* Allow server configuration parameters to be remotely modified
* Allow administrators to safely terminate individual sessions
-* Allow point-in-time recovery to archive partially filled logs
+
+ Right now, SIGTERM will terminate a session, but it is treated as
+ though the postmaster has paniced and shared memory might not be
+ cleaned up properly. A new signal is needed for safe termination.
+
+* Allow point-in-time recovery to archive partially filled write-ahead
+ logs
+
+ Currently only full WAL files are archived. This means that the most
+ recent transactions aren't available for recovery in case of a disk
+ failure.
* Improve replication solutions
o Automatic failover
+
+ The proper solution to this will probably the use of a master/slave
+ replication solution like Sloney and a connection pooling tool like
+ pgpool.
+
o Load balancing
- o Master/slave replication
- o Multi-master replication
- o Partition data across servers
- o Queries across databases or servers (two-phase commit)
+
+ You can use any of the master/slave replication servers to use a
+ standby server for data warehousing. To allow read/write queries to
+ multiple servers, you need multi-master replication like pgcluster.
+
o Allow replication over unreliable or non-persistent links
* Remove Money type, add money formatting for decimal type
* -Change factorial to return a numeric (Gavin)
* Change NUMERIC to enforce the maximum precision, and increase it
-* Add function to return compressed length of TOAST data values (Tom)
-* Allow INET subnet tests using non-constants to be indexed
+* Add function to return compressed length of TOAST data values
+* Allow INET subnet tests with non-constants to be indexed
* Add transaction_timestamp(), statement_timestamp(), clock_timestamp() functionality
-* Have sequence dependency track use of DEFAULT sequences, seqname.nextval
-* Disallow changing default expression of a SERIAL column
+
+ Current CURRENT_TIMESTAMP returns the start time of the current
+ transaction, and gettimeofday() returns the wallclock time. This will
+ make time reporting more consistent and will allow reporting of
+ the statement start time.
+
+* Have sequence dependency track use of DEFAULT sequences,
+ seqname.nextval (?)
+* Disallow changing default expression of a SERIAL column (?)
* Allow infinite dates just like infinite timestamps
* -Allow pg_dump to dump sequences using NO_MAXVALUE and NO_MINVALUE
-* Allow backend to output result sets in XML
* -Prevent whole-row references from leaking memory, e.g. SELECT COUNT(tab.*)
* Have initdb set DateStyle based on locale?
* Add pg_get_acldef(), pg_get_typedefault(), and pg_get_attrdef()
-* Add ALTER DOMAIN, AGGREGATE, CONVERSION, SEQUENCE ... OWNER TO
-* Allow to_char to print localized month names (Karel)
+* Allow to_char to print localized month names
* Allow functions to have a search path specified at creation time
* -Make LENGTH() of CHAR() not count trailing spaces
* Allow substring/replace() to get/set bit values
* Add GUC variable to allow output of interval values in ISO8601 format
-* Support composite types as table columns
+* -Support composite types as table columns
* Fix data types where equality comparison isn't intuitive, e.g. box
o Allow nulls in arrays
o Allow MIN()/MAX() on arrays
o Delay resolution of array expression type so assignment coercion
- can be performed on empty array expressions (Joe)
+ can be performed on empty array expressions
o Modify array literal representation to handle array index lower bound
of other than one
* BINARY DATA
- o Improve vacuum of large objects, like /contrib/vacuumlo
+ o Improve vacuum of large objects, like /contrib/vacuumlo (?)
o Add security checking for large objects
- o Make file in/out interface for TOAST columns, similar to large object
- interface (force out-of-line storage and no compression)
+
+ Currently large objects entries do not have owners. Permissions can
+ only be set at the pg_largeobject table level.
+
o Auto-delete large objects when referencing row is deleted
+ o Allow read/write into TOAST values like large objects
+
+ This requires the TOAST column to be stored EXTERNAL.
+
Multi-Language Support
======================
* Add NCHAR (as distinguished from ordinary varchar),
* Allow locale to be set at database creation
-* Allow locale on a per-column basis, default to ASCII
-* Optimize locale to have minimal performance impact when not used (Peter E)
+
+ Currently locale can only be set during initdb.
+
+* Allow encoding on a per-column basis
+
+ Right now only one encoding is allowed per database.
+
+* Optimize locale to have minimal performance impact when not used
* Support multiple simultaneous character sets, per SQL92
-* Improve Unicode combined character handling
-* Add octet_length_server() and octet_length_client() (Thomas, Tatsuo)
-* Make octet_length_client the same as octet_length() (?)
-* Prevent mismatch of frontend/backend encodings from converting bytea
+* Improve Unicode combined character handling (?)
+* Add octet_length_server() and octet_length_client()
+* Make octet_length_client() the same as octet_length()?
+* -Prevent mismatch of frontend/backend encodings from converting bytea
data from being interpreted as encoded strings
* -Fix upper()/lower() to work for multibyte encodings
Indexes
=======
-* -Order duplicate index entries on creation by tid for faster heap lookups
+* -Order duplicate index entries on creation by ctid for faster heap lookups
* Allow inherited tables to inherit index, UNIQUE constraint, and primary
key, foreign key [inheritance]
-* UNIQUE INDEX on base column not honored on inserts from inherited table
- INSERT INTO inherit_table (unique_index_col) VALUES (dup) should fail
- [inheritance]
+* UNIQUE INDEX on base column not honored on inserts/updates from
+ inherited table: INSERT INTO inherit_table (unique_index_col) VALUES
+ (dup) should fail [inheritance]
+
+ The main difficulty with this item is the problem of creating an index
+ that can spam more than one table.
+
* Add UNIQUE capability to non-btree indexes
* Add rtree index support for line, lseg, path, point
-* Use indexes for min() and max() or convert to SELECT col FROM tab ORDER
- BY col DESC LIMIT 1 if appropriate index exists and WHERE clause acceptible
+* Use indexes for MIN() and MAX()
+
+ MIN/MAX queries can already be rewritten as SELECT col FROM tab ORDER
+ BY col {DESC} LIMIT 1. Completing this item involves making this
+ transformation automatically.
+
* Use index to restrict rows returned by multi-key index when used with
- non-consecutive keys or OR clauses, so fewer heap accesses
-* Be smarter about insertion of already-ordered data into btree index
+ non-consecutive keys to reduce heap accesses
+
+ For an index on col1,col2,col3, and a WHERE clause of col1 = 5 and
+ col3 = 9, spin though the index checking for col1 and col3 matches,
+ rather than just col1
+
+* -Be smarter about insertion of already-ordered data into btree index
* Prevent index uniqueness checks when UPDATE does not modify the column
-* Use bitmaps to fetch heap pages in sequential order [performance]
+
+ Uniqueness (index) checks are done when updating a column even if the
+ column is not modified by the UPDATE.
+
+* Fetch heap pages matching index entries in sequential order [performance]
+
+ Rather than randomly accessing heap pages based on index entries, mark
+ heap pages needing access in a bitmap and do the lookups in sequential
+ order. Another method would be to sort heap ctids matching the index
+ before accessing the heap rows.
+
* Use bitmaps to combine existing indexes [performance]
+
+ Bitmap indexes allow single indexed columns to be combined to
+ dynamically create a composite index to match a specific query. Each
+ index is a bitmap, and the bitmaps are AND'ed or OR'ed to be combined.
+
* Allow use of indexes to search for NULLs
+
+ One solution is to create a partial index on an IS NULL expression.
+
* -Allow SELECT * FROM tab WHERE int2col = 4 to use int2col index, int8,
float4, numeric/decimal too
-* Add FILLFACTOR to btree index creation
* Add concurrency to GIST
-* Allow a single index to index multiple tables (for inheritance and subtables)
* Pack hash index buckets onto disk pages more efficiently
+ Currently no 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.
+
Commands
========
-* Add BETWEEN ASYMMETRIC/SYMMETRIC (Christopher)
+* Add BETWEEN ASYMMETRIC/SYMMETRIC
* Change LIMIT/OFFSET to use int8
* CREATE TABLE AS can not determine column lengths from expressions [atttypmod]
-* Allow UPDATE to handle complex aggregates [update]
-* Allow command blocks to ignore certain types of errors
+* Allow UPDATE to handle complex aggregates [update] (?)
+* -Allow command blocks to ignore certain types of errors
* Allow backslash handling in quoted strings to be disabled for portability
-* Allow UPDATE, DELETE to handle table aliases for self-joins [delete]
+
+ The use of C-style backslashes (.e.g. \n, \r) in quoted strings is not
+ SQL-spec compliant, so allow such handling to be disabled.
+
+* Allow DELETE to handle table aliases for self-joins [delete]
+
+ There is no way to specify use a table alias for the deleted table in
+ the DELETE WHERE clause because there is no FROM clause. Various
+ syntax extensions to add a FROM clause have been discussed. UPDATE
+ already has such an optional FROM clause.
+
* Add CORRESPONDING BY to UNION/INTERSECT/EXCEPT
-* Allow REINDEX to rebuild all indexes, remove /contrib/reindex
+* Allow REINDEX to rebuild all database indexes, remove /contrib/reindex
* Add ROLLUP, CUBE, GROUPING SETS options to GROUP BY
-* Add schema option to createlang
-* Allow savepoints / nested transactions [transactions] (Alvaro)
-* Use nested transactions to prevent syntax errors from aborting a transaction
+* Add a schema option to createlang
+* -Allow savepoints / nested transactions [transactions] (Alvaro)
+* -Use nested transactions to prevent syntax errors from aborting a transaction
* Allow UPDATE tab SET ROW (col, ...) = (...) for updating multiple columns
-* Allow SET CONSTRAINTS to be qualified by schema/table
-* Prevent COMMENT ON DATABASE from using a database name
+* Allow SET CONSTRAINTS to be qualified by schema/table name
+* -Prevent COMMENT ON DATABASE from using a database name
* -Add NO WAIT LOCKs
* Allow TRUNCATE ... CASCADE/RESTRICT
* Allow PREPARE of cursors
-* Allow LISTEN/NOTIFY to store info in memory rather than tables
+* Allow PREPARE to automatically determine parameter types based on the SQL
+ statement
+* 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.
+
* -COMMENT ON [ CAST | CONVERSION | OPERATOR CLASS | LARGE OBJECT | LANGUAGE ]
(Christopher)
* Dump large object comments in custom dump format
* 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 more ISOLATION LEVELS to be accepted
* Allow CREATE TABLE foo (f1 INT CHECK (f1 > 0) CHECK (f1 < 10)) to work
- by searching for non-conflicting constraint names, and prefix with table name
-* Use more reliable method for CREATE DATABASE to get a consistent copy of db
+ by searching for non-conflicting constraint names, and prefix with
+ table name?
+* Use more reliable method for CREATE DATABASE to get a consistent copy
+ of db?
+
+ Currently the system uses the operating system COPY command to create
+ new database.
+
+* Add C code to copy directories for use in creating new databases
* -Have psql \dn show only visible temp schemas using current_schemas()
* -Have psql '\i ~/<tab><tab>' actually load files it displays from home dir
-* Ignore temporary tables from other session when processing inheritance
+* Ignore temporary tables from other sessions when processing
+ inheritance?
* -Add GUC setting to make created tables default to WITHOUT OIDS
-* Have pg_ctl look at PGHOST in case it is a socket directory
-* Allow column-level privileges
-* Add a session mode to warn about non-standard SQL usage
+* Have pg_ctl look at PGHOST in case it is a socket directory?
+* Allow column-level GRANT/REVOKE privileges
+* Add a session mode to warn about non-standard SQL usage in queries
* Add MERGE command that does UPDATE/DELETE, or on failure, INSERT (rules, triggers?)
* Add ON COMMIT capability to CREATE TABLE AS SELECT
* Add NOVICE output level for helpful messages like automatic sequence/index creation
rows with DEFAULT value
o -ALTER TABLE ADD COLUMN column SERIAL doesn't create sequence because
of the item above
- o Have ALTER TABLE rename SERIAL sequences
+ o Have ALTER TABLE RENAME rename SERIAL sequence names
o -Allow ALTER TABLE to modify column lengths and change to binary
compatible types
- o Add ALTER DATABASE ... OWNER TO newowner
+ o -Add ALTER DATABASE ... OWNER TO newowner
o Add ALTER DOMAIN TYPE
o Allow ALTER TABLE ... ALTER CONSTRAINT ... RENAME
o Allow ALTER TABLE to change constraint deferrability and actions
o Disallow dropping of an inherited constraint
- o Allow the schema of objects to be changed
- o Add ALTER TABLESPACE to change location, name, owner
- o Allow objects to be moved between tablespaces
+ o Allow objects to be moved to different schemas
+ o Allow ALTER TABLESPACE to move to different directories
+ o Allow databases, schemas, and indexes 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
+ schema. Global system tables can never be moved.
+
+ o -Add ALTER DOMAIN, AGGREGATE, CONVERSION ... OWNER TO
+ o -Add ALTER SEQUENCE ... OWNER TO
* CLUSTER
o Automatically maintain clustering on a table
- o Add ALTER TABLE table SET WITHOUT CLUSTER (Christopher)
+
+ This would require some background daemon to restore clustering
+ during periods of low usage. It might also require tables to be only
+ paritally filled for easier reorganization.
+
+ o -Add ALTER TABLE table SET WITHOUT CLUSTER (Christopher)
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.
+
* COPY
o -Allow dump/load of CSV format
- o Allow COPY to report error lines and continue; optionally
- allow error codes to be specified; requires savepoints or can
- not be run in a multi-statement transaction
- o Allow COPY to understand \x as hex
- o Have COPY return number of rows loaded/unloaded
+ 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.
+
+ o Allow COPY to understand \x as a hex byte
+ o Have COPY return the number of rows loaded/unloaded (?)
* CURSOR
- o Allow UPDATE/DELETE WHERE CURRENT OF cursor using per-cursor tid
- stored in the backend (Gavin)
- o Prevent DROP of table being referenced by our own open cursor
+ o Allow UPDATE/DELETE WHERE CURRENT OF cursor
+
+ This requires using the row ctid to map cursor rows back to the
+ original heap row. This become more complicated if WITH HOLD cursors
+ are to be supported because WITH HOLD cursors have a copy of the row
+ and no FOR UPDATE lock.
+
+ o Prevent DROP TABLE from dropping a row referenced by its own open
+ cursor (?)
+
+ o Allow pooled connections to list all open WITH HOLD cursors
+
+ Because WITH HOLD cursors exist outside transactions, this allows
+ them to be listed so they can be closed.
* INSERT
- o Allow INSERT/UPDATE of system-generated oid value for a row
+ o Allow INSERT/UPDATE of the system-generated oid value for a row
o Allow INSERT INTO tab (col1, ..) VALUES (val1, ..), (val2, ..)
- o Allow INSERT/UPDATE ... RETURNING new.col or old.col; handle
- RULE cases (Philip)
+ o Allow INSERT/UPDATE ... RETURNING new.col or old.col
+
+ This is useful for returning the auto-generated key for an INSERT.
+ One complication is how to handle rules that run as part of
+ the insert.
* SHOW/SET
o Add SET PERFORMANCE_TIPS option to suggest INDEX, VACUUM, VACUUM
ANALYZE, and CLUSTER
- o Add SET PATH for schemas
- o Enforce rules for setting combinations
+ o Add SET PATH for schemas (?)
+
+ This is basically the same as SET search_path.
+
+ o Prevent conflicting SET options from being set
+
+ This requires a checking function to be called after the server
+ configuration file is read.
* SERVER-SIDE LANGUAGES
- o Allow PL/PgSQL's RAISE function to take expressions
+ o Allow PL/PgSQL's RAISE function to take expressions (?)
+
+ Currently only constants are supported.
+
o Change PL/PgSQL to use palloc() instead of malloc()
o -Allow Java server-side programming
- o Fix problems with complex temporary table creation/destruction
- without using PL/PgSQL EXECUTE, needs cache prevention/invalidation
- o Fix PL/pgSQL RENAME to work on variables other than OLD/NEW
- o Improve PL/PgSQL exception handling
+ o Handle references to temporary tables that are created, destroyed,
+ then recreated during a session, and EXECUTE is not used
+
+ This requires the cached PL/PgSQL byte code to be invalidated when
+ an object referenced in the function is changed.
+
+ o Fix PL/pgSQL RENAME to work on variables other than OLD/NEW
+ o Improve PL/PgSQL exception handling using savepoints
o -Allow PL/pgSQL parameters to be specified by name and type during definition
o Allow function parameters to be passed by name,
get_employee_salary(emp_id => 12345, tax_year => 2001)
- o Add PL/PgSQL packages
- o Add table function support to pltcl, plperl, plpython
+ o Add Oracle-style packages
+ o Add table function support to pltcl, plperl, plpython (?)
o Allow PL/pgSQL to name columns by ordinal position, e.g. rec.(3)
o Allow PL/pgSQL EXECUTE query_var INTO record_var;
o Add capability to create and call PROCEDURES
Clients
=======
-* Add XML capability to pg_dump and COPY, when backend XML capability
+* 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.
+
* -Allow psql \du to show users, and add \dg for groups
-* Allow clients to query a list of WITH HOLD cursors and prepared statements
* Add a libpq function to support Parse/DescribeStatement capability
-* Prevent libpq's PQfnumber() from lowercasing the column name
+* Prevent libpq's PQfnumber() from lowercasing the column name (?)
* -Allow pg_dump to dump CREATE CONVERSION (Christopher)
-* Allow libpq to return information about prepared queries
* -Make pg_restore continue after errors, so it acts more like pg_dump scripts
* Have psql show current values for a sequence
* Allow pg_dumpall to use non-text output formats
* Have pg_dump use multi-statement transactions for INSERT dumps
* 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.
+
* Allow pg_dump to use multiple -t and -n switches
+
+ This should be done by allowing a '-t schema.table' syntax.
+
* Fix oid2name and dbsize for tablespaces
-* Consistenly display privilege information for all objects in psql
+* Consistently display privilege information for all objects in psql
-* ECPG
+* ECPG (?)
o Docs
- o Implement set descriptor, using descriptor
- o Solve cardinality > 1 for input descriptors / variables
- o Improve error handling
+
+ Document differences between ecpg and the SQL standard and
+ information about the Informix-compatibility module.
+
+ o -Implement SET DESCRIPTOR
+ o Solve cardinality > 1 for input descriptors / variables (?)
+ o Improve error handling (?)
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 Allow multidimensional arrays
-
Referential Integrity
=====================
* Add MATCH PARTIAL referential integrity
-* Add deferred trigger queue file (Jan)
-* Implement dirty reads or shared row locks and use them in RI 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.
+
+* Implement dirty reads or shared row locks and use them in RI triggers (?)
* Enforce referential integrity for system tables
* Change foreign key constraint for array -> element to mean element
- in array
-* Allow DEFERRABLE UNIQUE constraints
+ 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 (Neil)
+* Support triggers on columns
* Have AFTER triggers execute after the appropriate SQL statement in a
function, not at the end of the function
* -Print table names with constraint names in error messages, or make constraint
names unique within a schema
* -Issue NOTICE if foreign key data requires costly test to match primary key
* 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 their underlying catalog data changes
+* Flush cached query plans when the dependent objects change
* -Use dependency information to dump data in proper order
* -Have pg_dump -c clear the database using dependency information
Exotic Features
===============
-* Add SQL99 WITH clause to SELECT (Tom, Fernando)
-* Add SQL99 WITH RECURSIVE to SELECT (Tom, Fernando)
-* Add pre-parsing phase that converts non-ANSI features to supported 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
-* Add two-phase commit to all distributed transactions with
- offline/readonly server status or administrator notification for failure
-* Allow cross-db queries with transaction semantics
+* 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
=====
-* Delay fsync() when other backends are about to commit too
- o Determine optimal commit_delay value
+* Improve commit_delay handling to reduce fsync()
* Determine optimal fdatasync/fsync, O_SYNC/O_DSYNC options
- o Allow multiple blocks to be written to WAL with one write()
-* Add an option to sync() before fsync()'ing checkpoint files
+* Allow multiple blocks to be written to WAL with one write()
+* Add an option to sync() before fsync()'ing checkpoint files
Cache
=====
-* Shared catalog cache, reduce lseek()'s by caching table size in shared area
* Add free-behind capability for large sequential scans [fadvise]
* Consider use of open/fcntl(O_DIRECT) to minimize OS caching
-* Cache last known per-tuple offsets to speed long tuple access, adjusting
- for NULLs and TOAST values
-* Use a fixed row count and a +/- count with MVCC visibility rules
- to allow fast COUNT(*) queries with no WHERE clause(?) [count]
+* Cache last known per-tuple offsets to speed long tuple access
+
+ While column offsets are already cached, the cache can not be used if
+ the tuple has NULLs or TOAST columns because these values change the
+ typical column offsets. Caching of such offsets could be accomplished
+ by remembering the previous offsets and use them again if the row has
+ the same pattern.
+
+* 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. [count]
Vacuum
======
-* Improve speed with indexes (perhaps recreate index instead)
+* 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
-* Provide automatic running of vacuum in the background in backend
+
+ 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.
+
+* -Provide automatic running of vacuum in the background in backend
rather than in /contrib (Matthew)
* Allow free space map to be auto-sized or warn when it is too small
-* Maintain a map of recently-expired of pages so vacuum can reclaim
- free space without a sequential scan
-* Have VACUUM FULL use REINDEX rather than index vacuum
+
+ The free space map is in shared memory so resizing is difficult.
+
+* Maintain a map of recently-expired rows
+
+ This allows vacuum to reclaim free space without requiring
+ a sequential scan
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
============
* 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 [pool]
-* Allow persistent backends [pool]
-* Create a transaction processor to aid in persistent connections and
- connection pooling [pool]
-* Do listen() in postmaster and accept() in pre-forked backend
-* Have pre-forked backend pre-connect to last requested database or pass
- file descriptor to backend pre-forked for matching database
+
+ 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
===============
-* Have after-change WAL write()'s write only modified data to kernel
-* Reduce number of after-change WAL writes; they exist only to gaurd against
- partial page writes [wal]
-* Turn off after-change writes if fsync is disabled (?)
+* 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.
+
+* 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
-* Find proper defaults for postgresql.conf WAL entries
-* Allow xlog directory location to be specified during initdb, perhaps
- using symlinks
+* 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.
Optimizer / Executor
====================
-* Missing optimizer selectivities for date, r-tree, etc
-* Allow ORDER BY ... LIMIT to select top values without sort or index
- using a sequential scan for highest/lowest values (Oleg)
-* Precompile SQL functions to avoid overhead (Neil)
+* 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
* Add utility to compute accurate random_page_cost value
* Improve ability to display optimizer analysis using OPTIMIZER_DEBUG
-* Use CHECK constraints to improve optimizer decisions
-* Check GUC geqo_threshold to see if it is still accurate
* Allow sorting, temp files, temp tables to use multiple work directories
-* Improve the planner to use CHECK constraints to prune the plan (for subtables)
+
+ This allows the I/O load to be spread across multiple disk drives.
* 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.
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 (?) [mmap]
-* Improve caching of attribute offsets when NULLs exist in the row
+
+ This would remove the requirement for SYSV SHM but would introduce
+ portability issues. Anonymous mmap is required to prevent I/O
+ overhead.
+
* Add a script to ask system configuration questions and tune postgresql.conf
-* Allow partitioning of table into multiple subtables
* -Use background process to write dirty shared buffers to disk
-* Investigate SMP context switching issues
* Use a phantom command counter for nested subtransactions to reduce
tuple overhead
+
Source Code
===========
* Remove warnings created by -Wcast-align
* Move platform-specific ps status display info from ps_status.c to ports
* Improve access-permissions check on data directory in Cygwin (Tom)
-* Add documentation for perl, including mention of DBI/DBD perl location
-* Create improved PostgreSQL introductory documentation for the PHP
- manuals
* Add optional CRC checksum to heap and index pages
* -Change representation of whole-tuple parameters to functions
* Clarify use of 'application' and 'command' tags in SGML docs
* Better document ability to build only certain interfaces (Marc)
* Remove or relicense modules that are not under the BSD license, if possible
-* Remove memory/file descriptor freeing before ereport(ERROR) (Bruce)
+* Remove memory/file descriptor freeing before ereport(ERROR)
* Acquire lock on a relation before building a relcache entry for it
* Research interaction of setitimer() and sleep() used by statement_timeout
* -Add checks for fclose() failure (Tom)
* -Change CVS ID to PostgreSQL
* -Exit postmaster if postgresql.conf can not be opened
* Rename /scripts directory because they are all C programs now
-* Allow creation of a libpq-only tarball
* Promote debug_query_string into a server-side function current_query()
* Allow the identifier length to be increased via a configure option
-* Improve CREATE SCHEMA regression test
* Allow binaries to be statically linked so they are more easily relocated
* Wire Protocol Changes
- o Dynamic character set handling
+ o Allow dynamic character set handling
o Add decoded type, length, precision
- o Compression?
+ 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>
-* Barry is Barry Lind <barry@xythos.com>
-* Billy is Billy G. Allie <Bill.Allie@mug.org>
+* Andrew is Andrew Dunstan
* 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 ?
* D'Arcy is D'Arcy J.M. Cain <darcy@druid.net> of The Cain Gang Ltd.
-* Dave is Dave Cramer <dave@fastcrypt.com>
-* Edmund is Edmund Mergl <E.Mergl@bawue.de>
-* Fernando is Fernando Nasser <fnasser@redhat.com> of Red Hat
+* Fabien is Fabien Coelho
* 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>
-* Karel is Karel Zak <zakkr@zf.jcu.cz>
* Jan is Jan Wieck <JanWieck@Yahoo.com> of Afilias, Inc.
* Joe is Joe Conway <mail@joeconway.com>
-* Liam is Liam Stewart <liams@redhat.com> of Red Hat
+* Karel is Karel Zak <zakkr@zf.jcu.cz>
+* Kris is Kris Jurka
+* Magnus is Magnus Haglander (?)
+* Manfred is Manfred Koizar <
* Marc is Marc Fournier <scrappy@hub.org> of PostgreSQL, Inc.
-* Mark is Mark Hollomon <mhh@mindspring.com>
* 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 M is Peter T Mount <peter@retep.org.uk> of Retep Software
-* Peter E is Peter Eisentraut <peter_e@gmx.net>
+* 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>
-* Ross is Ross J. Reedstrom <reedstrm@wallace.ece.rice.edu>
+* Simon is Simon Riggs
* Stephan is Stephan Szabo <sszabo@megazone23.bigpanda.com>
* Tatsuo is Tatsuo Ishii <t-ishii@sra.co.jp> of Software Research Assoc.
-* Thomas is Thomas Lockhart <lockhart@fourpalms.org> of Jet Propulsion Labratory
+* Teodor is
* Tom is Tom Lane <tgl@sss.pgh.pa.us> of Red Hat
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