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TODO

Blame
    • Bruce Momjian's avatar
      5894e7e3
      Add items: · 5894e7e3
      Bruce Momjian authored
      > * Prevent to_char() on interval from returning meaningless values
      >
      >   For example, to_char('1 month', 'mon') is meaningless.  Basically,
      >   most date-related parameters to to_char() are meaningless for
      >   intervals because interval is not anchored to a date.
      >
      > * Allow to_char() on interval values to accumulate the highest unit
      >   requested
      >
      > 	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
      >
      >   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.
      >
      5894e7e3
      History
      Add items:
      Bruce Momjian authored
      > * Prevent to_char() on interval from returning meaningless values
      >
      >   For example, to_char('1 month', 'mon') is meaningless.  Basically,
      >   most date-related parameters to to_char() are meaningless for
      >   intervals because interval is not anchored to a date.
      >
      > * Allow to_char() on interval values to accumulate the highest unit
      >   requested
      >
      > 	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
      >
      >   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.
      >
    TODO 39.16 KiB
    
    PostgreSQL TODO List
    ====================
    Current maintainer:	Bruce Momjian (pgman@candle.pha.pa.us)
    Last updated:		Sat May  7 00:24:29 EDT 2005
    
    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 8.1 release.#
    
    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.
    
    
    Administration
    ==============
    
    * Remove behavior of postmaster -o after making postmaster/postgres
      flags unique
    * Allow limits on per-db/user connections
    * Add group object ownership, so groups can rename/drop/grant on objects,
      so we can implement roles
    * 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 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
    * 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;
    
    * Allow GRANT/REVOKE permissions to be inherited by objects based on
      schema permissions
    * -Check for 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 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
    
      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.
    
    * Add a GUC variable to control the tablespace for temporary objects and
      sort files
    
      It could start with a random tablespace from a supplied list and cycle
      through the list.
    
    * All ability to monitor the use of temporary sort files
    * Allow WAL replay of CREATE TABLESPACE to work when the directory
      structure on the recovery computer is different from the original
    * Add "include file" functionality in postgresql.conf
    * Add session start time and last statement time to pg_stat_activity
    * Allow server logs to be remotely read using SQL commands
    * Allow pg_hba.conf settings to be controlled via SQL
    
      This would require a new global table that is dumped to flat file for
      use by the postmaster.  We do a similar thing for pg_shadow currently.
    
    * Allow administrators to safely terminate individual sessions
    
      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.
    
    * Un-comment all variables in postgresql.conf
    
      By not showing commented-out variables, we discourage people from
      thinking that re-commenting a variable returns it to its default.
      This has to address environment variables that are then overridden
      by config file values.  Another option is to allow commented values
      to return to their default values.
    
    * 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.  This could be triggered by a user command or a timer.
    
    * Automatically force archiving of partially-filled WAL files when 
      pg_stop_backup() is called or the server is stopped
    
      Doing this will allow administrators to know more easily when the
      archive contins all the files needed for point-in-time recovery.
    
    * Create dump tool for write-ahead logs for use in determining
      transaction id for point-in-time recovery
    * 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.
    
    * Add a function that returns the 'uptime' of the postmaster
    * Allow a warm standby system to also allow read-only queries
    
      This is useful for checking PITR recovery.
    
    * Allow the PITR process to be debugged and data examined
    * Add the client IP address and port to pg_stat_activity
    * Improve replication solutions
    	o Load balancing
    
    	  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
    
    * Support table partitioning that allows a single table to be stored
      in subtables that are partitioned based on the primary key or a WHERE
      clause
    
    
    Data Types
    ==========
    
    * Remove Money type, add money formatting for decimal type
    * Change NUMERIC to enforce the maximum precision, and increase it
    * Add function to return compressed length of TOAST data values
    * Allow INET subnet tests using non-constants to be indexed
    * Add transaction_timestamp(), statement_timestamp(), clock_timestamp()
      functionality
    
      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
    * Have initdb set DateStyle based on locale?
    * Add pg_get_acldef(), pg_get_typedefault(), and pg_get_attrdef()
    * Allow to_char() to print localized month names
    * Allow functions to have a schema search path specified at creation time
    * Allow substring/replace() to get/set bit values
    * Add a GUC variable to allow output of interval values in ISO8601 format
    * Fix data types where equality comparison isn't intuitive, e.g. box
    * Merge hardwired timezone names with the TZ database; allow either kind
      everywhere a TZ name is currently taken
    * Allow customization of the known set of TZ names (generalize the
      present australian_timezones hack)
    * Allow TIMESTAMP WITH TIME ZONE to store the original timezone
      information, either zone name or offset from UTC
    
      If the TIMESTAMP value is stored with a time zone name, interval 
      computations should adjust based on the time zone rules, e.g. adding
      24 hours to a timestamp would yield a different result from adding one
      day.
    
    * Prevent INET cast to CIDR if the unmasked bits are not zero, or
      zero the bits
    * Prevent INET cast to CIDR from droping netmask, SELECT '1.1.1.1'::inet::cidr
    * Add 'tid != tid ' operator for use in corruption recovery
    * Prevent to_char() on interval from returning meaningless values
    
      For example, to_char('1 month', 'mon') is meaningless.  Basically,
      most date-related parameters to to_char() are meaningless for
      intervals because interval is not anchored to a date.
    
    * Allow to_char() on interval values to accumulate the highest unit
      requested
    
    	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
    
      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.
    
    * Add ISO INTERVAL handling
    	o Add support for day-time syntax, INTERVAL '1 2:03:04' DAY TO SECOND
    	o Add support for year-month syntax, INTERVAL '50-6' YEAR TO MONTH
    	o For syntax that isn't uniquely ISO or PG syntax, like '1:30' or
    	  '1', 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'
    	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 Allow NULLs in arrays
    	o Allow MIN()/MAX() on arrays
    	o Delay resolution of array expression's data type so assignment
    	  coercion 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 Add security checking for large objects
    
    	  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
    
      Currently locale can only be set during initdb.
    
    * Allow encoding on a per-column basis
    
      Right now only one encoding is allowed per database.
    
    * 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()?
    
    
    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.
    
    * Add the functionality for WITH CHECK OPTION clause of CREATE VIEW
    * Allow NOTIFY in rules involving conditionals
    * Have views on temporary tables exist in the temporary namespace
    * Allow temporary views on non-temporary tables
    * Allow RULE recompilation
    
    
    Indexes
    =======
    
    * Allow inherited tables to inherit index, UNIQUE constraint, and primary
      key, foreign key
    * UNIQUE INDEX on base column not honored on INSERTs/UPDATEs from
      inherited table:  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 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()
    
      MIN/MAX queries can already be rewritten as SELECT col FROM tab ORDER
      BY col {DESC} LIMIT 1. Completing this item involves doing this
      transformation automatically.
    
    * Use index to restrict rows returned by multi-key index when used with
      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; also called skip-scanning.
    
    * 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.
    
    * Fetch heap pages matching index entries in sequential order
    
      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.
    
    * -Allow non-bitmap indexes to be combined by creating bitmaps in memory
    
      This feature allows separate indexes to be ANDed or ORed together.  This
      is particularly useful for data warehousing applications that need to
      query the database in an many permutations.  This feature scans an index
      and creates an in-memory bitmap, and allows that bitmap to be combined
      with other bitmap created in a similar way.  The bitmap can either index
      all TIDs, or be lossy, meaning it records just page numbers and each
      page tuple has to be checked for validity in a separate pass.
    
    * 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.
    
    * Allow use of indexes to search for NULLs
    
      One solution is to create a partial index on an IS NULL expression.
    
    * Add concurrency to GIST
    * 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.
    
    * Allow accurate statistics to be collected on indexes with more than
      one column or expression indexes, perhaps using per-index statistics
    * Add fillfactor to control reserved free space during index creation
    * Allow the creation of indexes with mixed ascending/descending specifiers
    
    
    Commands
    ========
    
    * Add BETWEEN ASYMMETRIC/SYMMETRIC
    * Change LIMIT/OFFSET and FETCH/MOVE to use int8
    * Allow CREATE TABLE AS to determine column lengths for complex
      expressions like SELECT col1 || col2
    * Allow UPDATE to handle complex aggregates [update] (?)
    * Allow backslash handling in quoted strings to be disabled for portability
    
      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.  However,
      disabling backslashes could break many third-party applications and tools.
    
    * Allow an alias to be provided for the target table in UPDATE/DELETE
    
      This is not SQL-spec but many DBMSs allow it.
    
    * -Allow additional tables to be specified in DELETE for joins
    
      UPDATE already allows this (UPDATE...FROM) but we need similar
      functionality in DELETE.  It's been agreed that the keyword should
      be USING, to avoid anything as confusing as DELETE FROM a FROM b.
    
    * Add CORRESPONDING BY to UNION/INTERSECT/EXCEPT
    * Allow REINDEX to rebuild all database indexes, remove /contrib/reindex
    * Add ROLLUP, CUBE, GROUPING SETS options to GROUP BY
    * Add a schema option to createlang
    * Allow UPDATE tab SET ROW (col, ...) = (...) for updating multiple columns
    * Allow SET CONSTRAINTS to be qualified by schema/table name
    * Allow TRUNCATE ... CASCADE/RESTRICT
    * Allow PREPARE of cursors
    * Allow PREPARE to automatically determine parameter types based on the SQL
      statement
    * 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.
    
    * 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.
    
    * 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.
    
    * 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
      a new database.
    
    * Add C code to copy directories for use in creating new databases
    * Have pg_ctl look at PGHOST in case it is a socket directory?
    * Allow column-level GRANT/REVOKE privileges
    * Add a GUC variable 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
    * Add COMMENT ON for all cluster global objects (users, groups, databases
      and tablespaces)
    * Add an option to automatically use savepoints for each statement in a
      multi-statement transaction.
    
      When enabled, this would allow errors in multi-statement transactions
      to be automatically ignored.
    
    * Make row-wise comparisons work per SQL spec
    * Add RESET CONNECTION command to reset all session state
    
      This would include resetting of all variables (RESET ALL), dropping of
      all temporary tables, removal of any NOTIFYs, cursors, prepared 
      queries(?), currval()s, etc.  This could be used for connection pooling. 
      We could also change RESET ALL to have this functionality.
    
    * Allow FOR UPDATE queries to do NOWAIT locks
    * Add GUC to issue notice about queries that use unjoined tables
    
    * ALTER
    	o Have ALTER TABLE RENAME rename SERIAL sequence names
    	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 objects to be moved to different schemas
    	o Allow ALTER TABLESPACE to move to different directories
    	o Allow databases and schemas to be moved to different tablespaces
    
    	  One complexity is whether moving a schema should move all existing
    	  schema objects or just define the location for future object creation.
    
    	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.
    
    
    * 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
    	  paritally 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.
    
    	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 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 (?)
    	o Allow COPY to optionally include column headings in the first line
    	o -Allow COPY FROM ... CSV to interpret newlines and carriage
    	  returns in data
    
    
    * 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 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
    
    	  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 (?)
    
    	  This is basically the same as SET search_path.
    
    
    * SERVER-SIDE LANGUAGES
    	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 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 Allow function parameters to be passed by name,
    	  get_employee_salary(emp_id => 12345, tax_year => 2001)
    	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
    	o Allow PL/pgSQL to handle %TYPE arrays, e.g. tab.col%TYPE[]
    	o Add MOVE to PL/pgSQL
    
    
    Clients
    =======
    
    * Add XML output to pg_dump and COPY
    
      We already allow XML to be stored in the database, and XPath queries
      can be used on that data using /contrib/xml2. It also supports XSLT
      transformations.
    
    * Add a libpq function to support Parse/DescribeStatement capability
    * Prevent libpq's PQfnumber() from lowercasing the column name (?)
    * Allow libpq to access SQLSTATE so pg_ctl can test for connection failure
    
      This would be used for checking if the server is up.
    
    * Have psql show current values for a sequence
    * Move psql backslash database information into the backend, use mnemonic
      commands? [psql]
    
      This would allow non-psql clients to pull the same information out of
      the database as psql.
    
    * Fix psql's display of schema information (Neil)
    * Allow psql \pset boolean variables to set to fixed values, rather than toggle
    * Consistently display privilege information for all objects in psql
    * Improve psql's handling of multi-line queries
    * pg_dump
    	o Have pg_dump use multi-statement transactions for INSERT dumps
    	o Allow pg_dump to use multiple -t and -n switches
    
    	  This should be done by allowing a '-t schema.table' syntax.
    
    	o Add dumping of comments on composite type columns
    	o Add dumping of comments on index columns
    	o Replace crude DELETE FROM method of pg_dumpall for cleaning of
    	  users and groups with separate DROP commands
    	o Add dumping and restoring of LOB comments
    	o Stop dumping CASCADE on DROP TYPE commands in clean mode
    	o Add full object name to the tag field.  eg. for operators we need
    	  '=(integer, integer)', instead of just '='.
    	o Add pg_dumpall custom format dumps.
    
    	  This is probably best done by combining pg_dump and pg_dumpall
    	  into a single binary.
    
    	o Add CSV output format
    	o Update pg_dump and psql to use the new COPY libpq API (Christopher)
    
    * ECPG
    	o Docs
    
    	  Document differences between ecpg and the SQL standard and
    	  information about the Informix-compatibility module.
    
    	o Solve cardinality > 1 for input descriptors / variables (?)
    	o Add a semantic check level, e.g. check if a table really exists
    	o fix handling of DB attributes that are arrays
    	o Use backend PREPARE/EXECUTE facility for ecpg where possible
    	o Implement SQLDA
    	o Fix nested C comments
    	o sqlwarn[6] should be 'W' if the PRECISION or SCALE value specified
    	o Make SET CONNECTION thread-aware, non-standard?
    	o Allow multidimensional arrays
    	* Add internationalized message strings
    
    
    Referential Integrity
    =====================
    
    * Add MATCH PARTIAL referential integrity
    * Add deferred trigger queue file
    
      Right now all deferred trigger information is stored in backend
      memory.  This could exhaust memory for very large trigger queues.
      This item involves dumping large queues into files.
    
    * -Implement 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 (?)
    * Allow triggers to be disabled [trigger]
    
      Currently the only way to disable triggers is to modify the system
      tables.
    
    * With disabled triggers, allow pg_dump to use ALTER TABLE ADD FOREIGN KEY
    
      If the dump is known to be valid, allow foreign keys to be added
      without revalidating the data.
    
    * Allow statement-level triggers to access modified rows
    * Support triggers on columns (Greg Sabino Mullane)
    * Remove CREATE CONSTRAINT TRIGGER
    
      This was used in older releases to dump referential integrity
      constraints.
    
    * Allow AFTER triggers on system tables
    
      System tables are modified in many places in the backend without going
      through the executor and therefore not causing triggers to fire. To
      complete this item, the functions that modify system tables will have
      to fire triggers.
    
    
    Dependency Checking
    ===================
    
    * Flush cached query plans when the dependent objects change
    * Track dependencies in function bodies and recompile/invalidate
    
    
    Exotic Features
    ===============
    
    * Add SQL99 WITH clause to SELECT
    * Add SQL99 WITH RECURSIVE to SELECT
    * Add pre-parsing phase that converts non-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
    * SQL*Net listener that makes PostgreSQL appear as an Oracle database
      to clients
    * Allow queries across databases or servers with transaction
      semantics
    
      Right now contrib/dblink can be used to issue such queries except it
      does not have locking or transaction semantics. Two-phase commit is
      needed to enable transaction semantics.
    
    * Add two-phase commit
    
      This will involve adding a way to respond to commit failure by either
      taking the server into offline/readonly mode or notifying the
      administrator
    
    
    PERFORMANCE
    ===========
    
    
    Fsync
    =====
    
    * Improve commit_delay handling to reduce fsync()
    * Determine optimal fdatasync/fsync, O_SYNC/O_DSYNC options
    * Allow multiple blocks to be written to WAL with one write()
    * Add an option to sync() before fsync()'ing checkpoint files
    
    
    Cache
    =====
    
    * Allow free-behind capability for large sequential scans, perhaps using
      posix_fadvise()
    
      Posix_fadvise() can control both sequential/random file caching and
      free-behind behavior, but it is unclear how the setting affects other
      backends that also have the file open, and the feature is not supported
      on all operating systems.
    
    * Consider use of open/fcntl(O_DIRECT) to minimize OS caching,
      especially for WAL writes
    * -Cache last known per-tuple offsets to speed long tuple access
    * Speed up COUNT(*)
    
      We could use a fixed row count and a +/- count to follow MVCC
      visibility rules, or a single cached value could be used and
      invalidated if anyone modifies the table.  Another idea is to
      get a count directly from a unique index, but for this to be
      faster than a sequential scan it must avoid access to the heap
      to obtain tuple visibility information.
    
    * Allow data to be pulled directly from indexes
    
      Currently indexes do not have enough tuple visibility information 
      to allow data to be pulled from the index without also accessing 
      the heap.  One way to allow this is to set a bit to index tuples 
      to indicate if a tuple is currently visible to all transactions 
      when the first valid heap lookup happens.  This bit would have to 
      be cleared when a heap tuple is expired.
    
    * Consider automatic caching of queries at various levels:
    	o Parsed query tree
    	o Query execute plan
    	o Query results
    
    * -Allow the size of the buffer cache used by temporary objects to be
      specified as a GUC variable
    
      Larger local buffer cache sizes requires more efficient handling of
      local cache lookups.
    
    * Improve the background writer
    
      Allow the background writer to more efficiently write dirty buffers
      from the end of the LRU cache and use a clock sweep algorithm to
      write other dirty buffers to reduced checkpoint I/O
    
    * Allow sequential scans to take advantage of other concurrent
      sequentiqal scans, also called "Synchronised Scanning"
    
      One possible implementation is to start sequential scans from the lowest
      numbered buffer in the shared cache, and when reaching the end wrap
      around to the beginning, rather than always starting sequential scans
      at the start of the table.
    
    Vacuum
    ======
    
    * Improve speed with indexes
    
      For large table adjustements during vacuum, it is faster to reindex
      rather than update the index.
    
    * Reduce lock time by moving tuples with read lock, then write
      lock and truncate table
    
      Moved tuples are invisible to other backends so they don't require a
      write lock. However, the read lock promotion to write lock could lead
      to deadlock situations.
    
    * -Add a warning when the free space map is too small
    * Maintain a map of recently-expired rows
    
      This allows vacuum to target specific pages for possible free space 
      without requiring a sequential scan.
    
    * Auto-vacuum
    	o Move into the backend code
    	o Scan the buffer cache to find free space or use background writer
    	o Use free-space map information to guide refilling
    	o Do VACUUM FULL if table is nearly empty?
    
    
    Locking
    =======
    
    * Make locking of shared data structures more fine-grained
    
      This requires that more locks be acquired but this would reduce lock
      contention, improving concurrency.
    
    * Add code to detect an SMP machine and handle spinlocks accordingly
      from distributted.net, http://www1.distributed.net/source,
      in client/common/cpucheck.cpp
    
      On SMP machines, it is possible that locks might be released shortly,
      while on non-SMP machines, the backend should sleep so the process
      holding the lock can complete and release it.
    
    * -Improve SMP performance on i386 machines
    
      i386-based SMP machines can generate excessive context switching
      caused by lock failure in high concurrency situations. This may be
      caused by CPU cache line invalidation inefficiencies.
    
    * Research use of sched_yield() for spinlock acquisition failure
    * Fix priority ordering of read and write light-weight locks (Neil)
    
    
    Startup Time
    ============
    
    * Experiment with multi-threaded backend [thread]
    
      This would prevent the overhead associated with process creation. Most
      operating systems have trivial process creation time compared to
      database startup overhead, but a few operating systems (WIn32,
      Solaris) might benefit from threading.  Also explore the idea of
      a single session using multiple threads to execute a query faster.
    
    * Add connection pooling
    
      It is unclear if this should be done inside the backend code or done
      by something external like pgpool. The passing of file descriptors to
      existing backends is one of the difficulties with a backend approach.
    
    
    Write-Ahead Log
    ===============
    
    * Eliminate need to write full pages to WAL before page modification [wal]
    
      Currently, to protect against partial disk page writes, we write the
      full page images to WAL before they are modified so we can correct any
      partial page writes during recovery.  These pages can also be
      eliminated from point-in-time archive files.
    
    * Reduce WAL traffic so only modified values are written rather than
      entire rows (?)
    * Turn off after-change writes if fsync is disabled
    
      If fsync is off, there is no purpose in writing full pages to WAL
    
    * Add WAL index reliability improvement to non-btree indexes
    * Allow the pg_xlog directory location to be specified during initdb
      with a symlink back to the /data location
    * Allow WAL information to recover corrupted pg_controldata
    * Find a way to reduce rotational delay when repeatedly writing
      last WAL page
    
      Currently fsync of WAL requires the disk platter to perform a full
      rotation to fsync again. One idea is to write the WAL to different
      offsets that might reduce the rotational delay.
    
    * Allow buffered WAL writes and fsync
    
      Instead of guaranteeing recovery of all committed transactions, this
      would provide improved performance by delaying WAL writes and fsync
      so an abrupt operating system restart might lose a few seconds of
      committed transactions but still be consistent.  We could perhaps
      remove the 'fsync' parameter (which results in an an inconsistent
      database) in favor of this capability.
    
    * Eliminate WAL logging for CREATE TABLE AS when not doing WAL archiving
    * Compress WAL entries [wal]
    * Change WAL to use 32-bit CRC, for performance reasons
    
    
    Optimizer / Executor
    ====================
    
    * Add missing optimizer selectivities for date, r-tree, etc
    * Allow ORDER BY ... LIMIT # to select high/low value without sort or
      index using a sequential scan for highest/lowest values
    
      Right now, if no index exists, ORDER BY ... LIMIT # requires we sort
      all values to return the high/low value.  Instead The idea is to do a 
      sequential scan to find the high/low value, thus avoiding the sort.
      MIN/MAX already does this, but not for LIMIT > 1.
    
    * Precompile SQL functions to avoid overhead
    * Create utility to compute accurate random_page_cost value
    * Improve ability to display optimizer analysis using OPTIMIZER_DEBUG
    * Have EXPLAIN ANALYZE highlight poor optimizer estimates
    * Use CHECK constraints to influence optimizer decisions
    
      CHECK constraints contain information about the distribution of values
      within the table. This is also useful for implementing subtables where
      a tables content is distributed across several subtables.
    
    * Consider using hash buckets to do DISTINCT, rather than sorting
    
      This would be beneficial when there are few distinct values.
    
    * ANALYZE should record a pg_statistic entry for an all-NULL column
    * Log queries where the optimizer row estimates were dramatically
      different from the number of rows actually found (?)
    
    
    Miscellaneous
    =============
    
    * Do async I/O for faster random read-ahead of data
    
      Async I/O allows multiple I/O requests to be sent to the disk with
      results coming back asynchronously.
    
    * Use mmap() rather than SYSV shared memory or to write WAL files (?)
    
      This would remove the requirement for SYSV SHM but would introduce
      portability issues. Anonymous mmap (or mmap to /dev/zero) is required
      to prevent I/O overhead.
    
    * Consider mmap()'ing files into a backend?
    
      Doing I/O to large tables would consume a lot of address space or
      require frequent mapping/unmapping.  Extending the file also causes
      mapping problems that might require mapping only individual pages,
      leading to thousands of mappings.  Another problem is that there is no
      way to _prevent_ I/O to disk from the dirty shared buffers so changes
      could hit disk before WAL is written.
    
    * Add a script to ask system configuration questions and tune postgresql.conf
    * Use a phantom command counter for nested subtransactions to reduce
      per-tuple overhead
    
    
    Source Code
    ===========
    
    * Add use of 'const' for variables in source tree
    * Rename some /contrib modules from pg* to pg_*
    * Move some things from /contrib into main tree
    * Move some /contrib modules out to their own project sites
    * Remove warnings created by -Wcast-align
    * Move platform-specific ps status display info from ps_status.c to ports
    * Add optional CRC checksum to heap and index pages
    * Improve documentation to build only interfaces (Marc)
    * Remove or relicense modules that are not under the BSD license, if possible
    * Remove memory/file descriptor freeing before ereport(ERROR)
    * Acquire lock on a relation before building a relcache entry for it
    * Promote debug_query_string into a server-side function current_query()
    * Allow the identifier length to be increased via a configure option
    * Remove Win32 rename/unlink looping if unnecessary
    * Remove kerberos4 from source tree?
    * Allow cross-compiling by generating the zic database on the target system
    * Improve NLS maintenace of libpgport messages linked onto applications
    * Allow ecpg to work with MSVC and BCC
    * -Make src/port/snprintf.c thread-safe
    * Add xpath_array() to /contrib/xml2 to return results as an array
    * Allow building in directories containing spaces
    
      This is probably not possible because 'gmake' and other compiler tools
      do not fully support quoting of paths with spaces.
    
    * Allow installing to directories containing spaces
    
      This is possible if proper quoting is added to the makefiles for the
      install targets.  Because PostgreSQL supports relocatable installs, it
      is already possible to install into a directory that doesn't contain 
      spaces and then copy the install to a directory with spaces.
    
    * Fix cross-compiling of time zone database via 'zic'
    * Win32
    	o Remove configure.in check for link failure when cause is found
    	o Remove readdir() errno patch when runtime/mingwex/dirent.c rev
    	  1.4 is released
    	o Remove psql newline patch when we find out why mingw outputs an
    	  extra newline
    	o Allow psql to use readline once non-US code pages work with
    	  backslashes
    	o Re-enable timezone output on log_line_prefix '%t' when a
    	  shorter timezone string is available
    	o Improve dlerror() reporting string
    	o Fix problem with shared memory on the Win32 Terminal Server
            o Add support for Unicode
    
    	  To fix this, the data needs to be converted to/from UTF16/UTF8
              so the Win32 wcscoll() can be used, and perhaps other functions
    	  like towupper().  However, UTF8 already works with normal
    	  locales but provides no ordering or character set classes.
    
    * Wire Protocol Changes
    	o Allow dynamic character set handling
    	o Add decoded type, length, precision
    	o Use compression?
    	o Update clients to use data types, typmod, schema.table.column names
    	  of result sets using new query protocol
    
    
    ---------------------------------------------------------------------------
    
    
    Developers who have claimed items are:
    --------------------------------------
    * Alvaro is Alvaro Herrera <alvherre@dcc.uchile.cl>
    * Andrew is Andrew Dunstan <andrew@dunslane.net>
    * Bruce is Bruce Momjian <pgman@candle.pha.pa.us> of Software Research Assoc.
    * Christopher is Christopher Kings-Lynne <chriskl@familyhealth.com.au> of
        Family Health Network
    * Claudio is Claudio Natoli <claudio.natoli@memetrics.com>
    * D'Arcy is D'Arcy J.M. Cain <darcy@druid.net> of The Cain Gang Ltd.
    * Fabien is Fabien Coelho <coelho@cri.ensmp.fr>
    * Gavin is Gavin Sherry <swm@linuxworld.com.au> of Alcove Systems Engineering
    * Greg is Greg Sabino Mullane <greg@turnstep.com>
    * Hiroshi is Hiroshi Inoue <Inoue@tpf.co.jp>
    * Jan is Jan Wieck <JanWieck@Yahoo.com> of Afilias, Inc.
    * Joe is Joe Conway <mail@joeconway.com>
    * Karel is Karel Zak <zakkr@zf.jcu.cz>
    * Magnus is Magnus Hagander <mha@sollentuna.net>
    * Marc is Marc Fournier <scrappy@hub.org> of PostgreSQL, Inc.
    * Matthew T. O'Connor <matthew@zeut.net>
    * Michael is Michael Meskes <meskes@postgresql.org> of Credativ
    * Neil is Neil Conway <neilc@samurai.com>
    * Oleg is Oleg Bartunov <oleg@sai.msu.su>
    * Peter is Peter Eisentraut <peter_e@gmx.net>
    * Philip is Philip Warner <pjw@rhyme.com.au> of Albatross Consulting Pty. Ltd.
    * Rod is Rod Taylor <pg@rbt.ca>
    * Simon is Simon Riggs <simon@2ndquadrant.com>
    * Stephan is Stephan Szabo <sszabo@megazone23.bigpanda.com>
    * Tatsuo is Tatsuo Ishii <t-ishii@sra.co.jp> of Software Research Assoc.
    * Tom is Tom Lane <tgl@sss.pgh.pa.us> of Red Hat