Todo
From PostgreSQL wiki
Revision as of 02:37, 15 February 2011 by Davidblewett (Talk | contribs)
This list contains all known PostgreSQL bugs and feature requests. If you would like to work on an item, please read the Developer FAQ first. There is also a development information page.
-
- marks ordinary, incomplete items
- [E] - marks items that are easier to implement
- [D]
- marks changes that are done, and will appear in the PostgreSQL 9.1 release.
For help on editing this list, please see Talk:Todo. Please do not add items here without discussion on the mailing list.
Administration
- Allow administrators to cancel multi-statement idle transactions
- This allows locks to be released, but it is complex to report the cancellation back to the client.
- Check for unreferenced table files created by transactions that were in-progress when the server terminated abruptly
- Set proper permissions on non-system schemas during db creation
- Currently all schemas are owned by the super-user because they are copied from the template1 database. However, since all objects are inherited from the template database, it is not clear that setting schemas to the db owner is correct.
- Allow log_min_messages to be specified on a per-module basis
- This would allow administrators to see more detailed information from specific sections of the backend, e.g. checkpoints, autovacuum, etc. Another idea is to allow separate configuration files for each module, or allow arbitrary SET commands to be passed to them. See also Logging Brainstorm.
- Simplify ability to create partitioned tables
- This would allow creation of partitioned tables without requiring creation of triggers or rules for INSERT/UPDATE/DELETE, and constraints for rapid partition selection. Options could include range and hash partition selection. See also Table partitioning
- [D] Allow auto-selection of partitioned tables for min/max() operations
- There was a patch on -hackers from July 2009, but it has not been merged: MIN/MAX optimization for partitioned table
- Allow custom variables to appear in pg_settings()
- Have custom variables be transaction safe
- Implement the SQL standard mechanism whereby REVOKE ROLE revokes only the privilege granted by the invoking role, and not those granted by other roles
- [D] Improve server security options
- Prevent query cancel packets from being replayed by an attacker, especially when using SSL
- Provide a way to query the log collector subprocess to determine what the currently active log file is
- [D] Allow the client to authenticate the server in a Unix-domain socket connection, e.g., using SO_PEERCRED
- Allow custom daemons to be automatically stopped/started along postmaster
- This allows easier administration of daemons like user job schedulers or replication-related daemons.
Configuration files
- [D] Allow pg_hba.conf to specify host names along with IP addresses
- Host name lookup could occur when the postmaster reads the pg_hba.conf file, or when the backend starts. Another solution would be to reverse lookup the connection IP and check that hostname against the host names in pg_hba.conf. We could also then check that the host name maps to the IP address.
- Allow postgresql.conf file values to be changed via an SQL API, perhaps using SET GLOBAL
- Allow the server to be stopped/restarted via an SQL API
- Consider normalizing fractions in postgresql.conf, perhaps using '%'
- Allow Kerberos to disable stripping of realms so we can check the username@realm against multiple realms
- Add functions to check correctness of configuration files before they are loaded "live"
- Improve LDAP authentication configuration options
- Add external tool to auto-tune some postgresql.conf parameters
- Add 'hostgss' pg_hba.conf option to allow GSS link-level encryption
- Process pg_hba.conf keywords as case-insensitive
Tablespaces
- Allow a database in tablespace t1 with tables created in tablespace t2 to be used as a template for a new database created with default tablespace t2
- Currently all objects in the default database tablespace must have default tablespace specifications. This is because new databases are created by copying directories. If you mix default tablespace tables and tablespace-specified tables in the same directory, creating a new database from such a mixed directory would create a new database with tables that had incorrect explicit tablespaces. To fix this would require modifying pg_class in the newly copied database, which we don't currently do.
- 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 WAL replay of CREATE TABLESPACE to work when the directory structure on the recovery computer is different from the original
- Allow per-tablespace quotas
Statistics Collector
- Allow statistics last vacuum/analyze execution times to be displayed without requiring track_counts to be enabled
- Clear table counters on TRUNCATE
- Allow the clearing of cluster-level statistics
- Resetting cluster-wide statistics
- pg_stat_reset_shared('bgwriter') (9.0) now handles the pg_stat_bgwriter subset of this
Point-In-Time Recovery (PITR)
- [E] Create dump tool for write-ahead logs for use in determining transaction id for point-in-time recovery
- This is useful for checking PITR recovery.
- [D] Allow recovery.conf to support the same syntax as postgresql.conf, including quoting
- Allow archive_mode to be changed without server restart?
- Consider avoiding WAL switching via archive_timeout if there has been no database activity
- [E] Expose pg_controldata via SQL interface
- Helpful for monitoring replicated databases
SSL
- Allow SSL authentication/encryption over unix domain sockets
- Allow SSL key file permission checks to be optionally disabled when sharing SSL keys with other applications
- Allow SSL CRL files to be re-read during configuration file reload, rather than requiring a server restart
-
Unlike SSL CRT files, CRL (Certificate Revocation List) files are updated frequently
Alternatively or additionally supporting OCSP (online certificate security protocol) would provide real-time revocation discovery without reloading
- Allow automatic selection of SSL client certificates from a certificate store
- Send full certificate server chain to client
Standby server mode
- Allow pg_xlogfile_name() to be used in recovery mode
- Fix things so that any such variables inherited from the server environment are intentionally *NOT* used for making SR connections.
- [D] Add a new privilege for connecting for streaming replication
- Add support for synchronous replication.
- [D] Add capability to take and send a base backup over the streaming replication connection, making it possible to initialize a new standby server from a running primary server without a WAL archive or other access to the primary server.
- Find a way to do hot file system backups on standby servers
- Change walsender so that it applies per-role settings
- Restructure configuration parameters for standby mode
Data Types
- Change NUMERIC to enforce the maximum precision
- [D] Reduce storage space for small NUMERICs
- Fix data types where equality comparison isn't intuitive, e.g. box
- Add support for public SYNONYMs
- Add support for SQL-standard GENERATED/IDENTITY columns
- Consider placing all sequences in a single table, or create a system view
- Consider a special data type for regular expressions
- Reduce BIT data type overhead using short varlena headers
- [D] Allow adding enumerated values to an existing enumerated data type
- Allow renaming and deleting enumerated values from an existing enumerated data type
- Support scoped IPv6 addresses in inet type
- Add JSON (JavaScript Object Notation) data type
- This would behave similar to the XML data type, which is stored as text, but allows element lookup and conversion functions.
- Considering improving performance of computing CHAR() value lengths
Domains
- Fix CREATE CAST on DOMAINs
- Allow domains to be cast
- Make domains work better with polymorphic functions
Dates and Times
- Allow infinite intervals just like infinite timestamps
- 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.
- Fix SELECT '0.01 years'::interval, '0.01 months'::interval
- Have timestamp subtraction not call justify_hours()?
- Improve timestamptz subtraction to be DST-aware
- Currently subtracting one date from another that crosses a daylight savings time adjustment can return '1 day 1 hour', but adding that back to the first date returns a time one hour in the future. This is caused by the adjustment of '25 hours' to '1 day 1 hour', and '1 day' is the same time the next day, even if daylight savings adjustments are involved.
- Fix interval display to support values exceeding 2^31 hours
- Add overflow checking to timestamp and interval arithmetic
- Add function to allow the creation of timestamps using parameters
Arrays
- Add support for arrays of domains
- Allow single-byte header storage for array elements
- Add function to detect if an array is empty
- Improve handling of empty arrays
- Improve handling of NULLs in arrays
Binary Data
- Improve vacuum of large objects, like contrib/vacuumlo?
- Auto-delete large objects when referencing row is deleted
- contrib/lo offers this functionality.
- Allow read/write into TOAST values like large objects
- This requires the TOAST column to be stored EXTERNAL.
- Add API for 64-bit large object access
MONEY Data Type
- Add locale-aware MONEY type, and support multiple currencies
- MONEY dumps in a locale-specific format making it difficult to restore to a system with a different locale
- Allow MONEY to be easily cast to/from other numeric data types
Text Search
- Allow dictionaries to change the token that is passed on to later dictionaries
- Consider a function-based API for '@@' searches
- Improve text search error messages
- Consider changing error to warning for strings larger than one megabyte
- tsearch and tsdicts regression tests fail in Turkish locale on glibc
- tsquery negator operator treated as part of lexeme
- Improve handling of plus signs in email address user names, and perhaps improve URL parsing
- Improve default parser, to more easily allow adding new tokens
XML
- Allow xml arrays to be cast to other data types
- Add XML Schema validation and xmlvalidate function (SQL:2008)
- Add xmlvalidatedtd variant to support validating against a DTD?
- Relax-NG validation; libxml2 supports this already
- Make it work reliably for non-UTF8 server encoding (xpath()) in particular is known to not work)
- Extra functions from SQL:2006: XMLDOCUMENT, XMLCAST, XMLTEXT
- XMLNAMESPACES support in XMLELEMENT and elsewhere
- XSLT support; already available in contrib/xml2, but needs API fixes and adaptation to xml type.
- XML Canonical: Convert XML documents to canonical form to compare them. libxml2 has support for this.
- Pretty-printing XML: Parse a document and serialize it back in some indented form. libxml2 might support this.
- XMLQUERY (from SQL/XML standard)
- In some cases shredding could be better option (if there is no need in keeping XML docs entirely; if we have already developed tools that understand only relational data; etc) -- it would be a separate module that implements annotated schema decomposition technique, similar to DB2 and SQL Server functionality.
- xpath_table needs to be implemented/implementable to get rid of contrib/xml2 [9]
- xpath_table is pretty broken anyway [10]
- [D] xpath_exists() is needed. It checks, whether or not the path specified exists in the XML value. (W/o this function we need to use weird "array_dims(xpath(...)) IS NOT NULL" syntax.)
- better handling of PIs and DTDs in xmlconcat() [13]
Functions
- Allow INET subnet tests using non-constants to be indexed
- Add INET overlaps operator, for use by exclusion constraints
- Allow to_date() and to_timestamp() to accept localized month names
- Add missing parameter handling in to_char()
- Throw an error from to_char() instead of printing a string of "#" when a number doesn't fit in the desired output format.
- discussed in "to_char, support for EEEE format"
- Allow to_char() on interval values to accumulate the highest unit requested
-
Some special format flag would be required to request such accumulation. Such functionality could also be added to EXTRACT. Prevent accumulation that crosses the month/day boundary because of the uneven number of days in a month.
- to_char(INTERVAL '1 hour 5 minutes', 'MI') => 65
- to_char(INTERVAL '43 hours 20 minutes', 'MI' ) => 2600
- to_char(INTERVAL '43 hours 20 minutes', 'WK:DD:HR:MI') => 0:1:19:20
- to_char(INTERVAL '3 years 5 months','MM') => 41
- Allow SQL-language functions to reference parameters by parameter name
- Currently SQL-language functions can only refer to dollar parameters, e.g. $1
- Add SPI_gettypmod() to return the typemod for a TupleDesc
- Enforce typmod for function inputs, function results and parameters for spi_prepare'd statements called from PLs
- Allow holdable cursors in SPI
- Tighten function permission checks
- Fix IS OF so it matches the ISO specification, and add documentation
- Add overlaps geometric operators that ignore point overlaps
- Implement Boyer-Moore searching in LIKE queries
- Prevent malicious functions from being executed with the permissions of unsuspecting users
- Index functions are safe, so VACUUM and ANALYZE are safe too. Triggers, CHECK and DEFAULT expressions, and rules are still vulnerable.
- Reduce memory usage of aggregates in set returning functions
- Fix /contrib/ltree operator
- Fix /contrib/btree_gist's implementation of inet indexing
- Fix inconsistent precedence of =, >, and < compared to <>, >=, and <=
- Fix regular expression bug when using complex back-references
- Have /contrib/dblink reuse unnamed connections
- Improve formatting of pg_get_viewdef() output
- [D] Add printf()-like functionality
- Fix to_number() handling for values not matching the format string
- Add function to dump pg_depend information cleanly
- Improve relation size functions such as pg_relation_size() to avoid producing an error when called against a no longer visible relation
Multi-Language Support
- Add NCHAR (as distinguished from ordinary varchar),
- [D] Allow more fine-grained collation selection
-
Right now the collation is fixed at database creation time.
- Re: Patch for collation using ICU
- FW: Win32 unicode vs ICU
- Re: FW: Win32 unicode vs ICU
- Proof of concept COLLATE support with patch
- For review: Initial support for COLLATE
- Proposed COLLATE implementation
- TODO item: locale per database patch (new iteration)
- Re: FW: Win32 unicode vs ICU
- Re: Fixed length data types issue
- [WIP] collation support revisited (phase 1)
- Todo:Collate
- Todo:ICU
- WIP patch: Collation support
- Re: WIP patch: Collation support
- PGDay.it collation discussion notes
- Unicode collation algorithm
- Add a LOCALE option to CREATE DATABASE, as a shorthand
- Support multiple simultaneous character sets, per SQL:2008
- Improve UTF8 combined character handling?
- Add octet_length_server() and octet_length_client()
- Make octet_length_client() the same as octet_length()?
- Fix problems with wrong runtime encoding conversion for NLS message files
- Add URL to more complete multi-byte regression tests
- Fix contrib/fuzzystrmatch to work with multibyte encodings
- Set client encoding based on the client operating system encoding
- Currently client_encoding is set in postgresql.conf, which defaults to the server encoding.
- Change memory allocation for multi-byte functions so memory is allocated inside conversion functions
- Currently we preallocate memory based on worst-case usage.
- Add ability to use case-insensitive regular expressions on multi-byte characters
- ILIKE already works with multi-byte characters
- Improve encoding of connection startup messages sent to the client
- Currently some authentication error messages are sent in the server encoding
- Have pg_stat_activity display query strings in the correct client encoding
- More sensible support for Unicode combining characters, normal forms
Views / Rules
- Automatically create rules on views so they are updateable, per SQL:2008
- We can only auto-create rules for simple views. For more complex cases users will still have to write rules manually.
- Add the functionality for WITH CHECK OPTION clause of CREATE VIEW
- Allow VIEW/RULE recompilation when the underlying tables change
- This is both difficult and controversial.
- Make it possible to use RETURNING together with conditional DO INSTEAD rules, such as for partitioning setups
- Add the ability to automatically create materialized views
- Right now materialized views require the user to create triggers on the main table to keep the summary table current. SQL syntax should be able to manage the triggers and summary table automatically. A more sophisticated implementation would automatically retrieve from the summary table when the main table is referenced, if possible. See Materialized Views for implementation details
- Improve ability to modify views via ALTER TABLE
- Prevent low-cost functions from seeing unauthorized view rows
SQL Commands
- Add CORRESPONDING BY to UNION/INTERSECT/EXCEPT
- Add ROLLUP, CUBE, GROUPING SETS options to GROUP BY
- [D] Fix TRUNCATE ... RESTART IDENTITY so its effect on sequences is rolled back on transaction abort
- Allow PREPARE of cursors
- Allow finer control over the caching of prepared query plans
- Currently anonymous (un-named) queries prepared via the wire protocol are replanned every time bind parameters are supplied --- allow SQL PREPARE to do the same. Also, allow control over replanning prepared queries either manually or automatically when statistics for execute parameters differ dramatically from those used during planning.
- Improve logging of prepared transactions recovered during startup
- Allow prepared transactions with temporary tables created and dropped in the same transaction, and when an ON COMMIT DELETE ROWS temporary table is accessed
- Add a GUC variable to warn about non-standard SQL usage in queries
- Add SQL-standard MERGE/REPLACE/UPSERT command
- MERGE is typically used to merge two tables. REPLACE or UPSERT command does UPDATE, or on failure, INSERT. See SQL MERGE for notes on the implementation details.
- Add NOVICE output level for helpful messages like automatic sequence/index creation
- Add GUC to issue notice about statements that use unjoined tables
- Allow EXPLAIN to identify tables that were skipped because of constraint_exclusion
- [D] Enable standard_conforming_strings by default
- When this is done, backslash-quote should be prohibited in non-E'' strings because of possible confusion over how such strings treat backslashes. Basically, '' is always safe for a literal single quote, while \' might or might not be based on the backslash handling rules.
- Simplify dropping roles that have objects in several databases
- Allow the count returned by SELECT, etc to be represented as an int64 to allow a higher range of values
- Add support for WITH RECURSIVE ... CYCLE
- Add DEFAULT .. AS OWNER so permission checks are done as the table owner
- This would be useful for SERIAL nextval() calls and CHECK constraints.
- Allow DISTINCT to work in multiple-argument aggregate calls
- Add column to pg_stat_activity that shows the progress of long-running commands like CREATE INDEX and VACUUM
- Allow INSERT/UPDATE/DELETE ... RETURNING inside a SELECT 'FROM' clause or target list
- Actually it would be saner to allow this in WITH
- Allow INSERT/UPDATE/DELETE ... RETURNING in common table expressions
- Add comments on system tables/columns using the information in catalogs.sgml
- Ideally the information would be pulled from the SGML file automatically.
- Prevent the specification of conflicting transaction read/write options
- Support LATERAL subqueries
- Lateral subqueries can reference columns of tables defined outside the subquery at the same level, i.e. laterally. For example, a LATERAL subquery in a FROM clause could reference tables defined in the same FROM clause. Currently only the columns of tables defined above subqueries are recognized.
- Add support for functional dependencies
- This would allow omitting GROUP BY columns when grouping by the primary key.
- Optimize ON COMMIT DELETE ROWS
- Currently deletions are excessively performed
- Allow DELETE and UPDATE to be used with LIMIT and ORDER BY
- Have DISCARD PLANS discard plans cached by functions
- DISCARD all should do the same.
CREATE
- Allow CREATE TABLE AS to determine column lengths for complex expressions like SELECT col1
- Have WITH CONSTRAINTS also create constraint indexes
- Move NOT NULL constraint information to pg_constraint
- Currently NOT NULL constraints are stored in pg_attribute without any designation of their origins, e.g. primary keys. One manifest problem is that dropping a PRIMARY KEY constraint does not remove the NOT NULL constraint designation. Another issue is that we should probably force NOT NULL to be propagated from parent tables to children, just as CHECK constraints are. (But then does dropping PRIMARY KEY affect children?)
- Prevent concurrent CREATE TABLE from sometimes returning a cryptic error message
- [D] Allow CREATE TABLE to optionally create a table if it does not already exist, without throwing an error
- The fact that tables contain data makes this more complex than other CREATE OR REPLACE operations.
- Add CREATE SCHEMA ... LIKE that copies a schema
- CREATE OR REPLACE FUNCTION might leave dependent objects depending on the function in inconsistent state
- Allow temporary tables to exist as empty by default in all sessions
- Allow the creation of "distinct" types
- Consider analyzing temporary tables when they are first used in a query
- Autovacuum cannot analyze or vacuum temporary tables.
- Allow an unlogged table to be changed to logged
UPDATE
- Allow UPDATE tab SET ROW (col, ...) = (SELECT...)
- Research self-referential UPDATEs that see inconsistent row versions in read-committed mode
- Improve performance of EvalPlanQual mechanism that rechecks already-updated rows
- This is related to the previous item, which questions whether it even has the right semantics
ALTER
- Have ALTER TABLE RENAME rename SERIAL sequence names
- [E] Allow ALTER TABLE ... ALTER CONSTRAINT ... RENAME
- Add ALTER TABLE RENAME CONSTRAINT
- Have ALTER SEQUENCE RENAME rename the sequence name stored in the sequence table
- Add ALTER DOMAIN to modify the underlying data type
- [E] Allow ALTER TABLE to change constraint deferrability and actions
- [D] Add missing object types for ALTER ... SET SCHEMA
- Allow ALTER TABLESPACE to move to different directories
- Allow moving system tables to other tablespaces, where possible
- Currently non-global system tables must be in the default database tablespace. Global system tables can never be moved.
- Have ALTER INDEX update the name of a constraint using that index
- Allow column display reordering by recording a display, storage, and permanent id for every column?
- [D] Allow an existing index to be marked as a table's primary key
- [D] Allow ALTER TYPE on composite types to perform operations similar to ALTER TABLE
- Don't require table rewrite on ALTER TABLE ... ALTER COLUMN TYPE, when the old and new data types are binary compatible
- Allow deactivating (and reactivating) indexes via ALTER TABLE
- <87hbegz5ir.fsf@cbbrowne.afilias-int.info> In discussion on FK activation/deactivation
CLUSTER
- Automatically maintain clustering on a table
- This might require some background daemon to maintain clustering during periods of low usage. It might also require tables to be only partially filled for easier reorganization. Another idea would be to create a merged heap/index data file so an index lookup would automatically access the heap data too. A third idea would be to store heap rows in hashed groups, perhaps using a user-supplied hash function.
- [D] Improve CLUSTER performance by sorting to reduce random I/O
- [D] Make CLUSTER VERBOSE more verbose.
- It is also used by new VACUUM FULL VERBOSE.
COPY
- 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.
- Allow COPY on a newly-created table to skip WAL logging
- On crash recovery, the table involved in the COPY would be removed or have its heap and index files truncated. One issue is that no other backend should be able to add to the table at the same time, which is something that is currently allowed. This currently is done if the table is created inside the same transaction block as the COPY because no other backends can see the table.
- Allow COPY FROM to create index entries in bulk
- Allow COPY in CSV mode to control whether a quoted zero-length string is treated as NULL
- Currently this is always treated as a zero-length string, which generates an error when loading into an integer column
- Improve COPY performance
- Allow COPY to report errors sooner
- Allow COPY to handle other number formats eg. the German notation. Best would be something like WITH DECIMAL ','.
- Allow a stalled COPY to exit if the backend is terminated
GRANT/REVOKE
- Allow SERIAL sequences to inherit permissions from the base table?
- Allow dropping of a role that has connection rights
DECLARE CURSOR
- Prevent DROP TABLE from dropping a table referenced by its own open cursor?
- Provide some guarantees about the behavior of cursors that invoke volatile functions
INSERT
- Allow INSERT/UPDATE of the system-generated oid value for a row
- In rules, allow VALUES() to contain a mixture of 'old' and 'new' references
SHOW/SET
- Add SET PERFORMANCE_TIPS option to suggest INDEX, VACUUM, VACUUM ANALYZE, and CLUSTER
- Rationalize the discrepancy between settings that use values in bytes and SHOW that returns the object count
LISTEN/NOTIFY
- Allow NOTIFY in rules involving conditionals
Window Functions
See TODO items for window functions.
- Support creation of user-defined window functions.
- We have the ability to create new window functions written in C. Is it worth the effort to create an API that would let them be written in PL/pgsql, etc?
- Implement full support for window framing clauses.
-
In addition to done clauses described in the latest doc, these clauses are not implemented yet.
- RANGE BETWEEN ... PRECEDING/FOLLOWING
- EXCLUDE
- Look at tuplestore performance issues.
- The tuplestore_in_memory() thing is just a band-aid, we ought to try to solve it properly. tuplestore_advance seems like a weak spot as well.
- Do we really need so much duplicated code between Agg and WindowAgg?
- Teach planner to evaluate multiple windows in the optimal order.
- Currently windows are always evaluated in the query-specified order.
- Implement DISTINCT clause in window aggregates.
- Some proprietary RDBMSs have implemented it already, so it helps with porting from those.
Integrity Constraints
Keys
- Improve deferrable unique constraints for cases with many conflicts
- The current implementation fires a trigger for each potentially conflicting row. This might not scale well for an update that changes many key values at once.
Referential Integrity
- Add MATCH PARTIAL referential integrity
- Change foreign key constraint for array -> element to mean element in array?
- Fix problem when cascading referential triggers make changes on cascaded tables, seeing the tables in an intermediate state
- Optimize referential integrity checks
Server-Side Languages
- Add support for polymorphic arguments and return types to languages other than PL/PgSQL
- Add support for OUT and INOUT parameters to languages other than PL/PgSQL
- Add more fine-grained specification of functions taking arbitrary data types
- Implement stored procedures
- This might involve the control of transaction state and the return of multiple result sets
PL/pgSQL
- Allow handling of %TYPE arrays, e.g. tab.col%TYPE[]
- Allow listing of record column names, and access to record columns via variables, e.g. columns := r.(*), tval2 := r.(colname)
- Allow row and record variables to be set to NULL constants, and allow NULL tests on such variables
- Because a row is not scalar, do not allow assignment from NULL-valued scalars.
- Consider keeping separate cached copies when search_path changes
- Improve handling of NULL row values vs. NULL rows
PL/Perl
- Allow regex operations in plperl using UTF8 characters in non-UTF8 encoded databases.
PL/Python
- Add table function support
- Add tracebacks
- Develop a trusted variant of PL/Python.
- Create a new restricted execution class that will allow passing function arguments in as locals. Passing them as globals means functions cannot be called recursively.
- Functions cache the input and output functions for their arguments, so the following will make PostgreSQL unhappy:
create table users (first_name text, last_name text); create function user_name(user) returns text as 'mycode' language plpython; select user_name(user) from users; alter table add column user_id integer; select user_name(user) from users;
You have to drop and create the function(s) each time its arguments are modified (not nice), or don't cache the input and output functions (slower?), or check if the structure of the argument has been altered (is this possible, easy, quick?) and recreate cache.
- Better documentation
- Add a DB-API compliant interface on top of the SPI interface
- Improve behaviour of exception functions and types
PL/Tcl
- Add table function support
- check encoding validity of values passed back to Postgres in function returns, trigger tuple changes, or SPI calls.
Clients
- Add a function like pg_get_indexdef() that report more detailed index information
pg_ctl
- Allow pg_ctl to work properly with configuration files located outside the PGDATA directory
- pg_ctl can not read the pid file because it isn't located in the config directory but in the PGDATA directory. The solution is to allow pg_ctl to read and understand postgresql.conf to find the data_directory value.
- Modify pg_ctl behavior and exit codes to make it easier to write an LSB conforming init script
-
It may be desirable to condition some of the changes on a command-line switch, to avoid breaking existing scripts. A Linux shell (sh) script is referenced which has been tested and seems to provide a high degree of conformance in multiple environments. Study of this script might suggest areas where pg_ctl could be modified to make writing an LSB conforming script easier; however, some aspects of that script would be unnecessary with other suggested changes to pg_ctl, and discussion on the lists did not reach consensus on support for all aspects of this script. Further discussion of particular changes is needed before beginning any work.
These threads should be studied for other ideas on improvements:
psql
- Have psql \ds show all sequences and their settings
- Have \d on a sequence indicate if the sequences is owned by a table
- Move psql backslash database information into the backend, use mnemonic commands?
- This would allow non-psql clients to pull the same information out of the database as psql.
- Make psql's \d commands more consistent in its handling of schemas
- Consistently display privilege information for all objects in psql
- Add auto-expanded mode so expanded output is used if the row length is wider than the screen width.
- Consider using auto-expanded mode for backslash commands like \df+.
- Prevent tab completion of SET TRANSACTION from querying the database and therefore preventing the transaction isolation level from being set.
- Currently SET <tab> causes a database lookup to check all supported session variables. This query causes problems because setting the transaction isolation level must be the first statement of a transaction.
- Add a \set variable to control whether \s displays line numbers
- Another option is to add \# which lists line numbers, and allows command execution.
- Prevent escape string warnings when object names have backslashes
- Have \d show child tables that inherit from the specified parent
- Include the symbolic SQLSTATE name in verbose error reports
- Add prompt escape to display the client and server versions
- Add option to wrap column values at whitespace boundaries, rather than chopping them at a fixed width.
- Currently, "wrapped" format chops values into fixed widths. Perhaps the word wrapping could use the same algorithm documented in the W3C specification.
- Add "auto" expanded mode that outputs in expanded format if "wrapped" mode can't wrap the output to the screen width
- Support the ReST table output format
- Details about the ReST format: http://docutils.sourceforge.net/rst.html#reference-documentation
- Add option to print advice for people familiar with other databases
- Consider showing TOAST and index sizes in \dt+
- Allow \dd to show constraint comments
- Add ability to edit views with \ev
- [D] Add \dL to show languages
- [D] Distinguish between unique indexes and unique constraints in \d+
- Fix FETCH_COUNT to handle SELECT ... INTO and WITH queries
- Prevent psql from sending remaining single-line multi-statement queries after reconnecting
- [E] Add \i option to bring in the specified file as a quoted literal. This would be useful for creating functions and other areas. Details still need to be worked out.
pg_dump / pg_restore
- [E] Add full object name to the tag field. eg. for operators we need '=(integer, integer)', instead of just '='.
- Add pg_dumpall custom format dumps?
- Avoid using platform-dependent locale names in pg_dumpall output
- Using native locale names puts roadblocks in the way of porting a dump to another platform. One possible solution is to get CREATE DATABASE to accept some agreed-on set of locale names and fix them up to meet the platform's requirements.
- Allow selection of individual object(s) of all types, not just tables
- In a selective dump, allow dumping of an object and all its dependencies
- Add options like pg_restore -l and -L to pg_dump
- Add support for multiple pg_restore -t options, like pg_dump
- pg_restore's -t switch is less useful than pg_dump's in quite a few ways: no multiple switches, no pattern matching, no ability to pick up indexes and other dependent items for a selected table. It should be made to handle this switch just like pg_dump does.
- Stop dumping CASCADE on DROP TYPE commands in clean mode
- Allow pg_dump --clean to drop roles that own objects or have privileges
- tgl says: if this is about pg_dumpall, it's done as of 8.4. If it's really about pg_dump, what does it mean? pg_dump has no business dropping roles.
- Remove unnecessary function pointer abstractions in pg_dump source code
- Allow pg_dump to utilize multiple CPUs and I/O channels by dumping multiple objects simultaneously
- The difficulty with this is getting multiple dump processes to produce a single dump output file. It also would require several sessions to share the same snapshot.
- Allow pg_restore to load different parts of the COPY data for a single table simultaneously
- Remove support for dumping from pre-7.3 servers
- In 7.3 and later, we can get accurate dependency information from the server. pg_dump still contains a lot of crufty code to try to deal with the lack of dependency info in older servers, but the usefulness of maintaining that code grows small.
- Allow pre/data/post files when schema and data are dumped separately, for performance reasons
- Refactor handling of database attributes between pg_dump and pg_dumpall
- Currently only pg_dumpall emits database attributes, such as ALTER DATABASE SET commands and database-level GRANTs. Many people wish that pg_dump would do that. One proposal is to let pg_dump issue such commands if the -C switch was used, but it's unclear whether that will satisfy the demand.
- Change pg_dump so that a comment on the dumped database is applied to the loaded database, even if the database has a different name.
- This will require new backend syntax, perhaps COMMENT ON CURRENT DATABASE. This is related to the previous item.
- Allow parallel restore of tar dumps
ecpg
- Docs
- Document differences between ecpg and the SQL standard and information about the Informix-compatibility module.
- Solve cardinality > 1 for input descriptors / variables?
- Add a semantic check level, e.g. check if a table really exists
- fix handling of DB attributes that are arrays
- Fix nested C comments
- [E] sqlwarn[6] should be 'W' if the PRECISION or SCALE value specified
- Make SET CONNECTION thread-aware, non-standard?
- Allow multidimensional arrays
- Implement COPY FROM STDIN
- Provide a way to specify size of a bytea parameter
- [E] Fix small memory leaks in ecpg
- Memory leaks in a short running application like ecpg are not really a problem, but make debugging more complicated
- Allow re-usage of cursor name variables
libpq
- Prevent PQfnumber() from lowercasing unquoted column names
- PQfnumber() should never have been doing lowercasing, but historically it has so we need a way to prevent it
- Allow statement results to be automatically batched to the client
- Currently all statement results are transferred to the libpq client before libpq makes the results available to the application. This feature would allow the application to make use of the first result rows while the rest are transferred, or held on the server waiting for them to be requested by libpq. One complexity is that a statement like SELECT 1/col could error out mid-way through the result set.
- Consider disallowing multiple queries in PQexec() as an additional barrier to SQL injection attacks
- Add PQexecf() that allows complex parameter substitution
- Add SQLSTATE and severity to errors generated within libpq itself
- Add code to detect client encoding and locale from the operating system environment
- Add support for interface/ipaddress binding to libpq
Triggers
- Improve storage of deferred trigger queue
- 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, or doing some kind of join to process all the triggers, some bulk operation, or a bitmap.
- Allow triggers to be disabled in only the current session.
- This is currently possible by starting a multi-statement transaction, modifying the system tables, performing the desired SQL, restoring the system tables, and committing the transaction. ALTER TABLE ... TRIGGER requires a table lock so it is not ideal for this usage.
- With disabled triggers, allow pg_dump to use ALTER TABLE ADD FOREIGN KEY
- If the dump is known to be valid, allow foreign keys to be added without revalidating the data.
- Allow statement-level triggers to access modified rows
- When statement-level triggers are defined on a parent table, have them fire only on the parent table, and fire child table triggers only where appropriate
- Allow AFTER triggers on system tables
- System tables are modified in many places in the backend without going through the executor and therefore not causing triggers to fire. To complete this item, the functions that modify system tables will have to fire triggers.
- Tighten trigger permission checks
- Allow BEFORE INSERT triggers on views
- Add database and transaction-level triggers
- Reduce locking requirements for creating a trigger
Inheritance
- Allow inherited tables to inherit indexes, UNIQUE constraints, and primary/foreign keys
- Honor UNIQUE INDEX on base column in INSERTs/UPDATEs on inherited table, e.g. INSERT INTO inherit_table (unique_index_col) VALUES (dup) should fail
- The main difficulty with this item is the problem of creating an index that can span multiple tables.
- Determine whether ALTER TABLE / SET SCHEMA should work on inheritance hierarchies (and thus support ONLY). If yes, implement it.
- ALTER TABLE variants sometimes support recursion and sometimes not, but this is poorly/not documented, and the ONLY marker would then be silently ignored. Clarify the documentation, and reject ONLY if it is not supported.
Indexes
- Prevent index uniqueness checks when UPDATE does not modify the column
- Uniqueness (index) checks are done when updating a column even if the column is not modified by the UPDATE. However, HOT already short-circuits this in common cases, so more work might not be helpful.
- 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.
- Re: Bitmap index AM
- Bitmap index thoughts
- Stream bitmaps
- Re: Bitmapscan changes - Requesting further feedback
- Updated bitmap index patch
- Reviewing new index types (was Re: [PATCHES] Updated bitmap indexpatch)
- Bitmap Indexes: request for feedback
- http://archives.postgresql.org/message-id/800923.27831.qm@web29010.mail.ird.yahoo.com
- Allow accurate statistics to be collected on indexes with more than one column or expression indexes, perhaps using per-index statistics
- Re: Simple join optimized badly?
- Stats for multi-column indexes
- Cross-column statistics revisited
- Multi-Dimensional Histograms
- http://archives.postgresql.org/pgsql-hackers/2010-12/msg00913.php
- http://archives.postgresql.org/pgsql-hackers/2010-12/msg02179.php
- http://archives.postgresql.org/pgsql-hackers/2011-01/msg00459.php
- Consider having a larger statistics target for indexed columns and expression indexes.
- Consider smaller indexes that record a range of values per heap page, rather than having one index entry for every heap row
- This is useful if the heap is clustered by the indexed values.
- Add REINDEX CONCURRENTLY, like CREATE INDEX CONCURRENTLY
- This is difficult because you must upgrade to an exclusive table lock to replace the existing index file. CREATE INDEX CONCURRENTLY does not have this complication. This would allow index compaction without downtime.
- Allow multiple indexes to be created concurrently, ideally via a single heap scan
- pg_restore allows parallel index builds, but it is done via subprocesses, and there is no SQL interface for this.
- Consider sorting entries before inserting into btree index
- Allow index scans to return matching index keys, not just the matching heap locations
- Allow creation of an index that can do comparisons to test if a value is between two column values
- Consider using "effective_io_concurrency" for index scans
- Currently only bitmap scans use this, which might be fine because most multi-row index scans use bitmap scans.
GIST
- Add more GIST index support for geometric data types
- Allow GIST indexes to create certain complex index types, like digital trees (see Aoki)
- Fix performance issues in contrib/seg and contrib/cube GiST support
GIN
- [D] Support empty indexed values (such as zero-element arrays) properly
- [D] Behave correctly for cases where some elements of an indexed value are NULL
- [D] Support queries that require a full scan
- [D] Improve GIN's handling of NULL array values
Hash
- Add UNIQUE capability to hash indexes
- Add hash WAL logging for crash recovery
- Allow multi-column hash indexes
Sorting
- Consider whether duplicate keys should be sorted by block/offset
- Consider being smarter about memory and external files used during sorts
- Consider detoasting keys before sorting
Fsync
- Determine optimal fdatasync/fsync, O_SYNC/O_DSYNC options and whether fsync does anything
- Ideally this requires a separate test program like /contrib/pg_test_fsync that can be run at initdb time or optionally later.
- Consider sorting writes during checkpoint
Cache Usage
- Speed up COUNT(*)
- We could use a fixed row count and a +/- count to follow MVCC visibility rules, or a single cached value could be used and invalidated if anyone modifies the table. Another idea is to get a count directly from a unique index, but for this to be faster than a sequential scan it must avoid access to the heap to obtain tuple visibility information.
- Provide a way to calculate an "estimated COUNT(*)"
- Perhaps by using the optimizer's cardinality estimates or random sampling.
- 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. The idea is to use the visibility map used for vacuum to avoid heap lookups on pages where all tuples are visible.
- Consider automatic caching of statements at various levels:
- Parsed query tree
- Query execute plan
- Query results
- Consider increasing internal areas (NUM_CLOG_BUFFERS) when shared buffers is increased
- Consider decreasing the amount of memory used by PrivateRefCount
- Consider allowing higher priority queries to have referenced buffer cache pages stay in memory longer
Vacuum
- Auto-fill the free space map by scanning the buffer cache or by checking pages written by the background writer
- Consider having single-page pruning update the visibility map
- https://commitfest.postgresql.org/action/patch_view?id=75
- Re: visibility maps and heap_prune
- Improve tracking of total relation tuple counts now that vacuum doesn't always scan the whole heap
- Bias FSM towards returning free space near the beginning of the heap file, in hopes that empty pages at the end can be truncated by VACUUM
- Make FSM return free space based on table clustering, to assist in maintaining clustering?
- Consider a more compact data representation for dead tuple locations within VACUUM
- Provide more information in order to improve user-side estimates of dead space bloat in relations
Auto-vacuum
- [E] Issue log message to suggest VACUUM FULL if a table is nearly empty?
- Prevent long-lived temporary tables from causing frozen-xid advancement starvation
- The problem is that autovacuum cannot vacuum them to set frozen xids; only the session that created them can do that.
- Prevent autovacuum from running if an old transaction is still running from the last vacuum
- Have free space allocation bias away from using trailing table pages
- This improves the chances of truncating the table during vacuum
- Have autoanalyze of parent tables occur when child tables are modified
Locking
- Fix priority ordering of read and write light-weight locks
- Fix problem when multiple subtransactions of the same outer transaction hold different types of locks, and one subtransaction aborts
- Allow UPDATEs on only non-referential integrity columns not to conflict with referential integrity locks
- Add idle_in_transaction_timeout GUC so locks are not held for long periods of time
- Improve deadlock detection when a page cleaning lock conflicts with a shared buffer that is pinned
- Detect deadlocks involving LockBufferForCleanup()
- Consider a lock timeout parameter
- [D] Consider improving serialized transaction behavior to avoid anomalies
Startup Time Improvements
- Experiment with multi-threaded backend for backend creation
- This would prevent the overhead associated with process creation. Most operating systems have trivial process creation time compared to database startup overhead, but a few operating systems (Win32, Solaris) might benefit from threading. Also explore the idea of a single session using multiple threads to execute a statement faster.
- Allow backends to change their database without restart
- This allows for faster server startup.
Write-Ahead Log
- Eliminate need to write full pages to WAL before page modification
- Currently, to protect against partial disk page writes, we write full page images to WAL before they are modified so we can correct any partial page writes during recovery. These pages can also be eliminated from point-in-time archive files.
- When full page writes are off, write CRC to WAL and check file system blocks on recovery
- If CRC check fails during recovery, remember the page in case a later CRC for that page properly matches.
- Write full pages during file system write and not when the page is modified in the buffer cache
- This allows most full page writes to happen in the background writer. It might cause problems for applying WAL on recovery into a partially-written page, but later the full page will be replaced from WAL.
- Reduce WAL traffic so only modified values are written rather than entire rows
- 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 WAL logging to be turned off for a table, but the table might be dropped or truncated during crash recovery
- Allow tables to bypass WAL writes and just fsync() dirty pages on commit. This should be implemented using ALTER TABLE, e.g. ALTER TABLE PERSISTENCE [ DROP | TRUNCATE | DEFAULT ]. Tables using non-default logging should not use referential integrity with default-logging tables. A table without dirty buffers during a crash could perhaps avoid the drop/truncate.
- Allow WAL logging to be turned off for a table, but the table would avoid being truncated/dropped
- To do this, only a single writer can modify the table, and writes must happen only on new pages so the new pages can be removed during crash recovery. Readers can continue accessing the table. Such tables probably cannot have indexes. One complexity is the handling of indexes on TOAST tables.
- Speed WAL recovery by allowing more than one page to be prefetched
- This should be done utilizing the same infrastructure used for prefetching in general to avoid introducing complex error-prone code in WAL replay.
- Improve WAL concurrency by increasing lock granularity
- Be more aggressive about creating WAL files
- Have resource managers report the duration of their status changes
- Move pgfoundry's xlogdump to /contrib and have it rely more closely on the WAL backend code
- Close deleted WAL files held open in *nix by long-lived read-only backends
Optimizer / Executor
- Improve selectivity functions for geometric operators
- Precompile SQL functions to avoid overhead
- Create utility to compute accurate random_page_cost value
- Consider increasing the default values of from_collapse_limit, join_collapse_limit, and/or geqo_threshold
- Improve ability to display optimizer analysis using OPTIMIZER_DEBUG
- Have EXPLAIN ANALYZE issue NOTICE messages when the estimated and actual row counts differ by a specified percentage
- Have EXPLAIN ANALYZE report rows as floating-point numbers
- Log statements where the optimizer row estimates were dramatically different from the number of rows actually found?
- Improve how ANALYZE computes in-doubt tuples
- Consider compressed annealing to search for query plans
- This might replace GEQO.
- Consider using a hash for joining to a large IN (VALUES ...) list
- Allow single batch hash joins to preserve outer pathkeys
- "lazy" hash tables - look up only the tuples that are actually requested
- Avoid building the same hash table more than once during the same query
- Avoid hashing for distinct and then re-hashing for hash join
- [D] Allow hashing to be used on arrays, if the element type is hashable
- Improve use of expression indexes for ORDER BY
- Modify the planner to better estimate caching effects
Background Writer
- Consider having the background writer update the transaction status hint bits before writing out the page
- Implementing this requires the background writer to have access to system catalogs and the transaction status log.
- Consider adding buffers the background writer finds reusable to the free list
- Automatically tune bgwriter_delay based on activity rather then using a fixed interval
- Consider whether increasing BM_MAX_USAGE_COUNT improves performance
- Test to see if calling PreallocXlogFiles() from the background writer will help with WAL segment creation latency
Concurrent Use of Resources
- 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.
- Asynchronous I/O Support
- Re: random_page_costs - are defaults of 4.0 realistic for SCSI RAID 1
- There's random access and then there's random access
- Bitmap index scan preread using posix_fadvise (Was: There's random access and then there's random access)
The above patch is already applied as of 8.4, but it still remains to figure out how to handle plain indexscans effectively.
- Experiment with multi-threaded backend for better I/O utilization
- This would allow a single query to make use of multiple I/O channels simultaneously. One idea is to create a background reader that can pre-fetch sequential and index scan pages needed by other backends. This could be expanded to allow concurrent reads from multiple devices in a partitioned table.
- Experiment with multi-threaded backend for better CPU utilization
- This would allow several CPUs to be used for a single query, such as for sorting or query execution.
- SMP scalability improvements
TOAST
- Allow user configuration of TOAST thresholds
- Reduce unnecessary cases of deTOASTing
- Reduce costs of repeat de-TOASTing of values
Miscellaneous Performance
- Use mmap() rather than SYSV for shared buffers?
- 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. We could also consider mmap() for writing WAL.
- Consider mmap()'ing files into a backend?
- Doing I/O to large tables would consume a lot of address space or require frequent mapping/unmapping. Extending the file also causes mapping problems that might require mapping only individual pages, leading to thousands of mappings. Another problem is that there is no way to _prevent_ I/O to disk from the dirty shared buffers so changes could hit disk before WAL is written.
- Add a script to ask system configuration questions and tune postgresql.conf
- Consider ways of storing rows more compactly on disk:
- Reduce the row header size?
- Consider reducing on-disk varlena length from four bytes to two because a heap row cannot be more than 64k in length
- Consider transaction start/end performance improvements
- Allow configuration of backend priorities via the operating system
- Though backend priorities make priority inversion during lock waits possible, research shows that this is not a huge problem.
- Consider increasing the minimum allowed number of shared buffers
- Consider if CommandCounterIncrement() can avoid its AcceptInvalidationMessages() call
- Consider Cartesian joins when both relations are needed to form an indexscan qualification for a third relation
- Consider not storing a NULL bitmap on disk if all the NULLs are trailing
- Sort large UPDATE/DELETEs so it is done in heap order
- Allow one transaction to see tuples using the snapshot of another transaction
- This would assist multiple backends in working together.
- Consider decreasing the I/O caused by updating tuple hint bits
- Avoid the requirement of freezing pages that are infrequently modified
- If all rows on a page are visible, it is possible to set a bit in the visibility map (once the visibility map is 100% reliable) and not need to freeze the page, avoiding a page rewrite
- Avoid reading in b-tree pages when replaying vacuum records in hot standby mode
Miscellaneous Other
- Deal with encoding issues for filenames in the server filesystem
- Deal with encoding issues in the output of localeconv()
- Provide schema name and other fields available from SQL GET DIAGNOSTICS in error reports
- [E] Provide fallback_application_name in contrib/pgbench, oid2name, and dblink.
Source Code
- Add use of 'const' for variables in source tree
- [E] 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
- One difficulty is how to prevent hint bit changes from affecting the computed CRC checksum.
- Consider a faster CRC32 algorithm
- Allow cross-compiling by generating the zic database on the target system
- Improve NLS maintenance of libpgport messages linked onto applications
- Improve the module installation experience (/contrib, etc)
- Use UTF8 encoding for NLS messages so all server encodings can read them properly
- Allow creation of universal binaries for Darwin
- Consider GnuTLS if OpenSSL license becomes a problem
- Consider making NAMEDATALEN more configurable in future releases
- Research use of signals and sleep wake ups
- Allow C++ code to more easily access backend code
- Consider simplifying how memory context resets handle child contexts
- Create three versions of libpgport to simplify client code
- Improve detection of shared memory segments being used by others by checking the SysV shared memory field 'nattch'
- Implement the non-threaded Avahi service discovery protocol
- Reduce data row alignment requirements on some 64-bit systems
- Restructure TOAST internal storage format for greater flexibility
- Add regression tests for pg_dump/restore
Documentation
- Convert single quotes to apostrophes in the PDF documentation
- Provide a manpage for postgresql.conf
- Change the manpage-generating toolchain to use the new XML-based docbook2x tools
- Consider changing documentation format from SGML to XML
- Document support for N' ' national character string literals, if it matches the SQL standard
- Add diagrams to the documentation
/contrib/pg_upgrade
- Remove copy_dir() code, or use it
- Handle large object comments
- This is difficult to do because the large object doesn't exist when --schema-only is loaded.
- Consider using pg_depend for checking object usage in version.c
- If reindex is necessary, allow it to be done in parallel with pg_dump custom format
- Migrate pg_statistic by dumping it out as a flat file, so analyze is not necessary
- pg_class.oid is not preserved so schema.tablename must be used.
- Improve testing, perhaps using the buildfarm
- The buildfarm has access to multiple versions of PostgreSQL.
- Create machine-readable output of pg_controldata
- This would avoid parsing its output. The problem is we need pg_controldata output from both the old and new clusters so we would need to support both formats.
Windows
- Remove configure.in check for link failure when cause is found
- Remove readdir() errno patch when runtime/mingwex/dirent.c rev 1.4 is released
- Allow psql to use readline once non-US code pages work with backslashes
- Fix problem with shared memory on the Win32 Terminal Server
- Improve signal handling
- Convert MSVC build system to remove most batch files
- Support pgxs when using MSVC
- Fix MSVC NLS support, like for to_char()
- Find a correct rint() substitute on Windows
- Fix global namespace issues when using multiple terminal server sessions
- Change from the current autoconf/gmake build system to cmake
- Improve consistency of path separator usage
Wire Protocol Changes
- Allow dynamic character set handling
- Add decoded type, length, precision
- Mark result columns as known-not-null when possible
- Provide more control over planner treatment of statements being prepared
- Use compression?
- Update clients to use data types, typmod, schema.table.column names of result sets using new statement protocol
Exotic Features
- Add pre-parsing phase that converts non-ISO syntax to supported syntax
- This could allow SQL written for other databases to run without modification.
- Allow plug-in modules to emulate features from other databases
- Add features of Oracle-style packages
- A package would be a schema with session-local variables, public/private functions, and initialization functions. It is also possible to implement these capabilities in any schema and not use a separate "packages" syntax at all.
- Consider allowing control of upper/lower case folding of unquoted identifiers
- Add autonomous transactions
- Give query progress indication
- Rethink our type system
Features We Do Not Want
The following features have been discussed ad nauseum on the PostgreSQL mailing lists and the consensus has been that the project is not interested in them. As such, if you are going to bring them up as potential features, you will want to be familiar with all of the arguments against these features which have been previously made over the years. If you decide to work on such features anyway, you should be aware that you face a higher-than-normal barrier to get the Project to accept them.
- All backends running as threads in a single process (not wanted)
- This eliminates the process protection we get from the current setup. Thread creation is usually the same overhead as process creation on modern systems, so it seems unwise to use a pure threaded model, and MySQL and DB2 have demonstrated that threads introduce as many issues as they solve. Threading specific operations such as I/O, seq scans, and connection management has been discussed and will probably be implemented to enable specific performance features. Moving to a threaded engine would also require halting all other work on PostgreSQL for one to two years.
- "Oracle-style" optimizer hints (not wanted)
- Optimizer hints, as implemented in Oracle and other RDBMSes, are used to work around problems in the optimizer and introduce upgrade and maintenance issues. We would rather have such problems reported and fixed. We have discussed a more sophisticated system of per-class cost adjustment instead, but a specification remains to be developed. See Optimizer Hints Discussion for further information.
- Embedded server (not wanted)
- While PostgreSQL clients runs fine in limited-resource environments, the server requires multiple processes and a stable pool of resources to run reliably 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. Besides, there are several very mature embedded SQL databases already available.
- Obfuscated function source code (not wanted)
- Obfuscating function source code has minimal protective benefits because anyone with super-user access can find a way to view the code. At the same time, it would greatly complicate backups and other administrative tasks. To prevent non-super-users from viewing function source code, remove SELECT permission on pg_proc.
- Indeterminate behavior for the GROUP BY clause (not wanted)
- At least one other database product allows specification of a subset of the result columns which GROUP BY would need to be able to provide predictable results; the server is free to return any value from the group. This is not viewed as a desirable feature. PostgreSQL 9.1 will allow result columns that are not referenced by GROUP BY if a primary key for the same table is referenced in GROUP BY.
