PostgreSQL TODO List ==================== Current maintainer: Bruce Momjian (bruce@momjian.us) Last updated: Wed Aug 13 21:57:34 EDT 2008 The most recent version of this document can be viewed at http://www.postgresql.org/docs/faqs.TODO.html. #A hyphen, "-", marks changes that will appear in the upcoming 8.4 release.# #A percent sign, "%", marks items that are easier to implement.# This list contains all known PostgreSQL bugs and feature requests. If you would like to work on an item, please read the Developer's FAQ first. There is also a developer's wiki at http://developer.postgresql.org. Administration ============== * -Allow administrators to safely terminate individual sessions either via an SQL function or SIGTERM * Check for unreferenced table files created by transactions that were in-progress when the server terminated abruptly http://archives.postgresql.org/pgsql-patches/2006-06/msg00096.php * Set proper permissions on non-system schemas during db creation Currently all schemas are owned by the super-user because they are copied from the template1 database. However, since all objects are inherited from the template database, it is not clear that setting schemas to the db owner is correct. * -Add function to report the time of the most recent server reload * Allow log_min_messages to be specified on a per-module basis This would allow administrators to see more detailed information from specific sections of the backend, e.g. checkpoints, autovacuum, etc. Another idea is to allow separate configuration files for each module, or allow arbitrary SET commands to be passed to them. * Simplify ability to create partitioned tables This would allow creation of partitioned tables without requiring creation of triggers or rules for INSERT/UPDATE/DELETE, and constraints for rapid partition selection. Options could include range and hash partition selection. http://archives.postgresql.org/pgsql-hackers/2007-03/msg00375.php http://archives.postgresql.org/pgsql-hackers/2007-04/msg00151.php http://archives.postgresql.org/pgsql-hackers/2008-01/msg00028.php http://archives.postgresql.org/pgsql-hackers/2008-01/msg00248.php http://archives.postgresql.org/pgsql-hackers/2008-01/msg00387.php http://archives.postgresql.org/pgsql-hackers/2008-01/msg00413.php * Allow auto-selection of partitioned tables for min/max() operations * Allow more complex user/database default GUC settings Currently ALTER USER and ALTER DATABASE support per-user and per-database defaults. Consider adding per-user-and-database defaults so things like search_path can be defaulted for a specific user connecting to a specific database. * Allow custom variables to appear in pg_settings() * Allow custom variable classes that can restrict who can set the values http://archives.postgresql.org/pgsql-hackers/2006-11/msg00911.php * Implement the SQL standard mechanism whereby REVOKE ROLE revokes only the privilege granted by the invoking role, and not those granted by other roles http://archives.postgresql.org/pgsql-bugs/2007-05/msg00010.php * Allow SSL authentication/encryption over unix domain sockets http://archives.postgresql.org/pgsql-hackers/2007-12/msg00924.php * Allow SSL key file permission checks to be optionally disabled when sharing SSL keys with other applications http://archives.postgresql.org/pgsql-bugs/2007-12/msg00069.php * Allow SSL client certificate names to be checked against the client hostname This is already implemented in libpq/fe-secure.c::verify_peer_name_matches_certificate() but the code is commented out. * Add 'hostgss' pg_hba.conf option to allow GSS link-level encryption http://archives.postgresql.org/pgsql-hackers/2008-07/msg01454.php * Improve server security options http://archives.postgresql.org/pgsql-hackers/2008-04/msg01875.php http://archives.postgresql.org/pgsql-hackers/2008-05/msg00000.php * Configuration files o Allow pg_hba.conf to specify host names along with IP addresses Host name lookup could occur when the postmaster reads the pg_hba.conf file, or when the backend starts. Another solution would be to reverse lookup the connection IP and check that hostname against the host names in pg_hba.conf. We could also then check that the host name maps to the IP address. http://archives.postgresql.org/pgsql-hackers/2008-06/msg00569.php o %Allow postgresql.conf file values to be changed via an SQL API, perhaps using SET GLOBAL o Allow the server to be stopped/restarted via an SQL API o Issue a warning if a change-on-restart-only postgresql.conf value is modified and the server config files are reloaded o Consider normalizing fractions in postgresql.conf, perhaps using '%' http://archives.postgresql.org/pgsql-hackers/2007-06/msg00550.php o Allow Kerberos to disable stripping of realms so we can check the username@realm against multiple realms http://archives.postgresql.org/pgsql-hackers/2007-11/msg00009.php o Add functions to syntax check configuration files o Improve LDAP authentication configuration options http://archives.postgresql.org/pgsql-hackers/2008-04/msg01745.php o Add external tool to auto-tune some postgresql.conf parameters http://archives.postgresql.org/pgsql-hackers/2008-06/msg00000.php * Tablespaces o Allow a database in tablespace t1 with tables created in tablespace t2 to be used as a template for a new database created with default tablespace t2 Currently all objects in the default database tablespace must have default tablespace specifications. This is because new databases are created by copying directories. If you mix default tablespace tables and tablespace-specified tables in the same directory, creating a new database from such a mixed directory would create a new database with tables that had incorrect explicit tablespaces. To fix this would require modifying pg_class in the newly copied database, which we don't currently do. o Allow reporting of which objects are in which tablespaces This item is difficult because a tablespace can contain objects from multiple databases. There is a server-side function that returns the databases which use a specific tablespace, so this requires a tool that will call that function and connect to each database to find the objects in each database for that tablespace. o Allow WAL replay of CREATE TABLESPACE to work when the directory structure on the recovery computer is different from the original o Allow per-tablespace quotas * Statistics Collector o Allow statistics collector information to be pulled from the collector process directly, rather than requiring the collector to write a filesystem file twice a second? o Reduce file system activity overhead of statistics file pgstat.stat http://archives.postgresql.org/pgsql-general/2007-12/msg00106.php o Allow statistics last vacuum/analyze execution times to be displayed without requiring stats_row_level to be enabled http://archives.postgresql.org/pgsql-docs/2007-04/msg00028.php o Clear table counters on TRUNCATE http://archives.postgresql.org/pgsql-hackers/2008-04/msg00169.php * Point-In-Time Recovery (PITR) o Allow a warm standby system to also allow read-only statements http://archives.postgresql.org/pgsql-hackers/2007-03/msg00050.php o %Create dump tool for write-ahead logs for use in determining transaction id for point-in-time recovery This is useful for checking PITR recovery. o Allow recovery.conf to support the same syntax as postgresql.conf, including quoting http://archives.postgresql.org/pgsql-hackers/2006-12/msg00497.php o -Fix server restart problem when the server was shutdown during a PITR backup http://archives.postgresql.org/pgsql-hackers/2007-11/msg00800.php o Recreate pg_xlog/archive_status/ if it doesn't exist after restoring from a PITR backup http://archives.postgresql.org/pgsql-hackers/2007-12/msg00487.php o Reduce PITR WAL file size by removing full page writes and by removing trailing bytes to improve compression Data Types ========== * Change NUMERIC to enforce the maximum precision * Reduce storage space for small NUMERICs http://archives.postgresql.org/pgsql-hackers/2007-02/msg01331.php http://archives.postgresql.org/pgsql-patches/2007-02/msg00505.php http://archives.postgresql.org/pgsql-hackers/2007-06/msg00715.php * Fix data types where equality comparison isn't intuitive, e.g. box * Add support for public SYNONYMs http://archives.postgresql.org/pgsql-hackers/2006-03/msg00519.php * Fix CREATE CAST on DOMAINs http://archives.postgresql.org/pgsql-hackers/2006-05/msg00072.php http://archives.postgresql.org/pgsql-hackers/2006-09/msg01681.php * Allow domains to be cast http://archives.postgresql.org/pgsql-hackers/2003-06/msg01206.php http://archives.postgresql.org/pgsql-hackers/2007-08/msg00289.php * Add support for SQL-standard GENERATED/IDENTITY columns http://archives.postgresql.org/pgsql-hackers/2006-07/msg00543.php http://archives.postgresql.org/pgsql-hackers/2006-08/msg00038.php http://archives.postgresql.org/pgsql-hackers/2007-05/msg00344.php http://archives.postgresql.org/pgsql-patches/2007-05/msg00076.php http://archives.postgresql.org/pgsql-hackers/2008-02/msg00604.php * Improve XML support http://developer.postgresql.org/index.php/XML_Support * Consider placing all sequences in a single table, or create a system view http://archives.postgresql.org/pgsql-hackers/2008-03/msg00008.php * Allow the UUID type to accept non-standard formats http://archives.postgresql.org/pgsql-hackers/2008-02/msg01214.php * Consider a special data type for regular expressions http://archives.postgresql.org/pgsql-hackers/2007-08/msg01067.php * Reduce BIT data type overhead using short varlena headers http://archives.postgresql.org/pgsql-general/2007-12/msg00273.php * Allow xml arrays to be cast to other data types http://archives.postgresql.org/pgsql-hackers/2007-09/msg00981.php http://archives.postgresql.org/pgsql-hackers/2007-10/msg00231.php http://archives.postgresql.org/pgsql-hackers/2007-11/msg00471.php * Simplify integer cross-data-type operators http://archives.postgresql.org/pgsql-bugs/2008-01/msg00189.php * Allow adding/renaming/removing enumerated values to an existing enumerated data type http://archives.postgresql.org/pgsql-hackers/2008-04/msg01718.php * Dates and Times o Allow infinite dates and intervals just like infinite timestamps o Merge hardwired timezone names with the TZ database; allow either kind everywhere a TZ name is currently taken o Allow TIMESTAMP WITH TIME ZONE to store the original timezone information, either zone name or offset from UTC If the TIMESTAMP value is stored with a time zone name, interval computations should adjust based on the time zone rules. http://archives.postgresql.org/pgsql-hackers/2004-10/msg00705.php o Fix SELECT '0.01 years'::interval, '0.01 months'::interval o Add a GUC variable to allow output of interval values in ISO8601 format o Have timestamp subtraction not call justify_hours()? http://archives.postgresql.org/pgsql-sql/2006-10/msg00059.php o Improve timestamptz subtraction to be DST-aware Currently subtracting one date from another that crosses a daylight savings time adjustment can return '1 day 1 hour', but adding that back to the first date returns a time one hour in the future. This is caused by the adjustment of '25 hours' to '1 day 1 hour', and '1 day' is the same time the next day, even if daylight savings adjustments are involved. o Fix interval display to support values exceeding 2^31 hours o Add overflow checking to timestamp and interval arithmetic o Extend timezone code to allow 64-bit values so we can represent years beyond 2038 http://archives.postgresql.org/pgsql-hackers/2006-09/msg01363.php o -Use LC_TIME for localized weekday/month names, rather than LC_MESSAGES http://archives.postgresql.org/pgsql-hackers/2006-11/msg00390.php o Add ISO INTERVAL handling http://archives.postgresql.org/pgsql-hackers/2006-01/msg00250.php http://archives.postgresql.org/pgsql-bugs/2006-04/msg00248.php o Support ISO INTERVAL syntax if units cannot be determined from the string, and are supplied after the string The SQL standard states that the units after the string specify the units of the string, e.g. INTERVAL '2' MINUTE should return '00:02:00'. The current behavior has the units restrict the interval value to the specified unit or unit range, INTERVAL '70' SECOND returns '00:00:10'. For syntax that isn't uniquely ISO or PG syntax, like '1' or '1:30', treat as ISO if there is a range specification clause, and as PG if there no clause is present, e.g. interpret '1:30' MINUTE TO SECOND as '1 minute 30 seconds', and interpret '1:30' as '1 hour, 30 minutes'. This makes common cases like SELECT INTERVAL '1' MONTH SQL-standard results. The SQL standard supports a limited number of unit combinations and doesn't support unit names in the string. The PostgreSQL syntax is more flexible in the range of units supported, e.g. PostgreSQL supports '1 year 1 hour', while the SQL standard does not. o Add support for year-month syntax, INTERVAL '50-6' YEAR TO MONTH o Interpret INTERVAL '1 year' MONTH as CAST (INTERVAL '1 year' AS INTERVAL MONTH), and this should return '12 months' o Round or truncate values to the requested precision, e.g. INTERVAL '11 months' AS YEAR should return one or zero o Support precision, CREATE TABLE foo (a INTERVAL MONTH(3)) * Arrays o Delay resolution of array expression's data type so assignment coercion can be performed on empty array expressions o Add support for arrays of domains http://archives.postgresql.org/pgsql-patches/2007-05/msg00114.php o Allow single-byte header storage for array elements * Binary Data o Improve vacuum of large objects, like contrib/vacuumlo? o Add security checking for large objects o Auto-delete large objects when referencing row is deleted contrib/lo offers this functionality. o Allow read/write into TOAST values like large objects This requires the TOAST column to be stored EXTERNAL. o Add API for 64-bit large object access http://archives.postgresql.org/pgsql-hackers/2005-09/msg00781.php * MONEY data type * Add locale-aware MONEY type, and support multiple currencies http://archives.postgresql.org/pgsql-general/2005-08/msg01432.php http://archives.postgresql.org/pgsql-hackers/2007-03/msg01181.php * MONEY dumps in a locale-specific format making it difficult to restore to a system with a different locale * Allow MONEY to be easily cast to/from other numeric data types * Text Search o Allow dictionaries to change the token that is passed on to later dictionaries http://archives.postgresql.org/pgsql-patches/2007-11/msg00081.php o Consider a function-based API for '@@' searches http://archives.postgresql.org/pgsql-hackers/2007-11/msg00511.php o Improve text search error messages http://archives.postgresql.org/pgsql-hackers/2007-10/msg00966.php http://archives.postgresql.org/pgsql-hackers/2007-11/msg01146.php o Consider changing error to warning for strings larger than one megabyte http://archives.postgresql.org/pgsql-bugs/2008-02/msg00190.php http://archives.postgresql.org/pgsql-patches/2008-03/msg00062.php Functions ========= * Allow INET subnet tests using non-constants to be indexed * Allow to_date() and to_timestamp() accept localized month names * Fix to_date()-related functions to consistently issue errors http://archives.postgresql.org/pgsql-hackers/2007-02/msg00915.php * Add missing parameter handling in to_char() http://archives.postgresql.org/pgsql-hackers/2005-12/msg00948.php * Allow substring/replace() to get/set bit values * Allow to_char() on interval values to accumulate the highest unit requested Some special format flag would be required to request such accumulation. Such functionality could also be added to EXTRACT. Prevent accumulation that crosses the month/day boundary because of the uneven number of days in a month. o to_char(INTERVAL '1 hour 5 minutes', 'MI') => 65 o to_char(INTERVAL '43 hours 20 minutes', 'MI' ) => 2600 o to_char(INTERVAL '43 hours 20 minutes', 'WK:DD:HR:MI') => 0:1:19:20 o to_char(INTERVAL '3 years 5 months','MM') => 41 * Implement inlining of set-returning functions defined in SQL * Allow SQL-language functions to return results from RETURNING queries http://archives.postgresql.org/pgsql-hackers/2006-10/msg00665.php * Allow SQL-language functions to reference parameters by parameter name Currently SQL-language functions can only refer to dollar parameters, e.g. $1 * Add SPI_gettypmod() to return the typemod for a TupleDesc * Enforce typmod for function inputs, function results and parameters for spi_prepare'd statements called from PLs http://archives.postgresql.org/pgsql-hackers/2007-01/msg01403.php * Allow holdable cursors in SPI * Tighten function permission checks http://archives.postgresql.org/pgsql-hackers/2006-12/msg00568.php * Fix IS OF so it matches the ISO specification, and add documentation http://archives.postgresql.org/pgsql-patches/2003-08/msg00060.php http://archives.postgresql.org/pgsql-hackers/2007-02/msg00060.php * Add missing operators for geometric data types Some geometric types do not have the full suite of geometric operators, e.g. box @> point * Implement Boyer-Moore searching in strpos() http://archives.postgresql.org/pgsql-patches/2007-08/msg00012.php * Prevent malicious functions from being executed with the permissions of unsuspecting users Index functions are safe, so VACUUM and ANALYZE are safe too. Triggers, CHECK and DEFAULT expressions, and rules are still vulnerable. http://archives.postgresql.org/pgsql-hackers/2008-01/msg00268.php * Reduce memory usage of aggregates in set returning functions http://archives.postgresql.org/pgsql-performance/2008-01/msg00031.php * -Add temporal versions of generate_series() http://archives.postgresql.org/pgsql-hackers/2007-04/msg01180.php * Add array_accum() and array_to_set() functions for arrays The standards specify array_agg() and UNNEST. http://archives.postgresql.org/pgsql-hackers/2007-08/msg00464.php * Fix /contrib/ltree operator http://archives.postgresql.org/pgsql-bugs/2007-11/msg00044.php * Fix inconsistent precedence of =, >, and < compared to <>, >=, and <= http://archives.postgresql.org/pgsql-bugs/2007-12/msg00145.php * Fix regular expression bug when using complex back-references http://archives.postgresql.org/pgsql-bugs/2007-10/msg00000.php * Have /contrib/dblink reuse unnamed connections http://archives.postgresql.org/pgsql-hackers/2007-10/msg00895.php * Add SQL-standard array_agg() and unnest() array functions http://archives.postgresql.org/pgsql-hackers/2008-01/msg01017.php * Allow calling of a procedure outside a SELECT that can control the transaction state http://archives.postgresql.org/pgsql-hackers/2007-10/msg01375.php Multi-Language Support ====================== * Add NCHAR (as distinguished from ordinary varchar), * Allow locale to be set at database creation Currently locale can only be set during initdb. No global tables have locale-aware columns. However, the database template used during database creation might have locale-aware indexes. The indexes would need to be reindexed to match the new locale. * Allow encoding on a per-column basis optionally using the ICU library; Add CREATE COLLATE Right now only one encoding is allowed per database. http://archives.postgresql.org/pgsql-hackers/2005-03/msg00932.php http://archives.postgresql.org/pgsql-patches/2005-08/msg00039.php http://archives.postgresql.org/pgsql-patches/2005-08/msg00309.php http://archives.postgresql.org/pgsql-hackers/2005-09/msg00110.php http://archives.postgresql.org/pgsql-patches/2005-09/msg00020.php http://archives.postgresql.org/pgsql-hackers/2005-12/msg01121.php http://archives.postgresql.org/pgsql-hackers/2006-01/msg00767.php http://archives.postgresql.org/pgsql-patches/2006-03/msg00233.php http://archives.postgresql.org/pgsql-hackers/2006-09/msg00662.php http://wiki.postgresql.org/wiki/Todo:Collate http://wiki.postgresql.org/wiki/Todo:ICU * Support multiple simultaneous character sets, per SQL92 * Improve UTF8 combined character handling? * Add octet_length_server() and octet_length_client() * Make octet_length_client() the same as octet_length()? * Fix problems with wrong runtime encoding conversion for NLS message files * Add URL to more complete multi-byte regression tests http://archives.postgresql.org/pgsql-hackers/2005-07/msg00272.php * Fix ILIKE and regular expressions to handle case insensitivity properly in multibyte encodings http://archives.postgresql.org/pgsql-bugs/2005-10/msg00001.php http://archives.postgresql.org/pgsql-patches/2005-11/msg00173.php * Set client encoding based on the client operating system encoding Currently client_encoding is set in postgresql.conf, which defaults to the server encoding. http://archives.postgresql.org/pgsql-hackers/2006-08/msg01696.php * Change memory allocation for multi-byte functions so memory is allocated inside conversion functions Currently we preallocate memory based on worst-case usage. Views / Rules ============= * Automatically create rules on views so they are updateable, per SQL99 We can only auto-create rules for simple views. For more complex cases users will still have to write rules manually. http://archives.postgresql.org/pgsql-hackers/2006-03/msg00586.php http://archives.postgresql.org/pgsql-patches/2006-08/msg00255.php * Add the functionality for WITH CHECK OPTION clause of CREATE VIEW * Allow VIEW/RULE recompilation when the underlying tables change Another issue is whether underlying table changes should be reflected in the view, e.g. should SELECT * show additional columns if they are added after the view is created. * Make it possible to use RETURNING together with conditional DO INSTEAD rules, such as for partitioning setups http://archives.postgresql.org/pgsql-hackers/2007-09/msg00577.php * Add the ability to automatically create materialized views Right now materialized views require the user to create triggers on the main table to keep the summary table current. SQL syntax should be able to manager the triggers and summary table automatically. A more sophisticated implementation would automatically retrieve from the summary table when the main table is referenced, if possible. * Improve ability to modify views via ALTER TABLE http://archives.postgresql.org/pgsql-hackers/2008-05/msg00691.php http://archives.postgresql.org/pgsql-hackers/2008-07/msg01410.php SQL Commands ============ * Add CORRESPONDING BY to UNION/INTERSECT/EXCEPT * Add ROLLUP, CUBE, GROUPING SETS options to GROUP BY * %Allow SET CONSTRAINTS to be qualified by schema/table name * %Add a separate TRUNCATE permission Currently only the owner can TRUNCATE a table because triggers are not called, and the table is locked in exclusive mode. * Fix TRUNCATE ... RESTART IDENTITY so its affect on sequences is rolled back on transaction abort * Allow PREPARE of cursors * Allow finer control over the caching of prepared query plans Currently queries prepared via the libpq API are planned on first execute using the supplied parameters --- allow SQL PREPARE to do the same. Also, allow control over replanning prepared queries either manually or automatically when statistics for execute parameters differ dramatically from those used during planning. * Improve logging of prepared transactions recovered during startup http://archives.postgresql.org/pgsql-hackers/2006-11/msg00092.php * Improve failure message when DROP DATABASE is used on a database that has prepared transactions * Allow prepared transactions with temporary tables created and dropped in the same transaction, and when an ON COMMIT DELETE ROWS temporary table is accessed http://archives.postgresql.org/pgsql-hackers/2008-03/msg00047.php * 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. This is similar to UPDATE, then for unmatched rows, INSERT. Whether concurrent access allows modifications which could cause row loss is implementation independent. To implement this cleanly requires that the table have a unique index so duplicate checking can be easily performed. It is possible to do it without a unique index if we require the user to LOCK the table before the MERGE. http://archives.postgresql.org/pgsql-hackers/2005-11/msg00501.php http://archives.postgresql.org/pgsql-hackers/2005-11/msg00536.php http://archives.postgresql.org/pgsql-hackers/2008-04/msg01157.php http://archives.postgresql.org/pgsql-hackers/2008-04/msg01475.php http://archives.postgresql.org/pgsql-hackers/2008-04/msg01890.php * Add NOVICE output level for helpful messages like automatic sequence/index creation * Add GUC to issue notice about statements that use unjoined tables * Allow EXPLAIN to identify tables that were skipped because of constraint_exclusion * Allow EXPLAIN output to be more easily processed by scripts, perhaps XML * Enable standard_conforming_strings * Make standard_conforming_strings the default in 8.5? When this is done, backslash-quote should be prohibited in non-E'' strings because of possible confusion over how such strings treat backslashes. Basically, '' is always safe for a literal single quote, while \' might or might not be based on the backslash handling rules. * Simplify dropping roles that have objects in several databases * Allow COMMENT ON to accept an expression rather than just a string * Allow the count returned by SELECT, etc to be represented as an int64 to allow a higher range of values * Add SQL99 WITH clause to SELECT * Add SQL:2003 WITH RECURSIVE (hierarchical) queries to SELECT http://archives.postgresql.org/pgsql-hackers/2007-01/msg01375.php http://archives.postgresql.org/pgsql-hackers/2008-02/msg00642.php http://archives.postgresql.org/pgsql-patches/2007-03/msg00139.php http://archives.postgresql.org/pgsql-hackers/2007-11/msg01334.php http://archives.postgresql.org/pgsql-patches/2008-01/msg00105.php http://archives.postgresql.org/pgsql-patches/2008-03/msg00327.php * Add DEFAULT .. AS OWNER so permission checks are done as the table owner This would be useful for SERIAL nextval() calls and CHECK constraints. * Allow DISTINCT to work in multiple-argument aggregate calls * Add column to pg_stat_activity that shows the progress of long-running commands like CREATE INDEX and VACUUM http://archives.postgresql.org/pgsql-patches/2008-04/msg00203.php * Implement SQL:2003 window functions http://archives.postgresql.org/pgsql-hackers/2008-06/msg00380.php http://archives.postgresql.org/pgsql-hackers/2008-07/msg00232.php * Allow INSERT/UPDATE ... RETURNING inside a SELECT 'FROM' clause or target list http://archives.postgresql.org/pgsql-general/2006-09/msg00803.php http://archives.postgresql.org/pgsql-hackers/2006-10/msg00693.php http://archives.postgresql.org/pgsql-hackers/2008-06/msg00124.php * Increase locking when DROPing objects so dependent objects cannot get dropped while the DROP operation is happening http://archives.postgresql.org/pgsql-hackers/2007-01/msg00937.php * -Allow AS in "SELECT col AS label" to be optional in certain cases * Allow INSERT ... DELETE ... RETURNING, namely allow the DELETE ... RETURNING to supply values to the INSERT http://archives.postgresql.org/pgsql-hackers/2008-02/thrd2.php#00979 * Add comments on system tables/columns using the information in catalogs.sgml Ideally the information would be pulled from the SGML file automatically. * Improve reporting of UNION type mismatches http://archives.postgresql.org/pgsql-hackers/2007-04/msg00944.php http://archives.postgresql.org/pgsql-hackers/2008-03/msg00597.php * CREATE o Allow CREATE TABLE AS to determine column lengths for complex expressions like SELECT col1 || col2 o Have WITH CONSTRAINTS also create constraint indexes http://archives.postgresql.org/pgsql-patches/2007-04/msg00149.php o Have CONSTRAINT cname NOT NULL record the contraint name Right now pg_attribute.attnotnull records the NOT NULL status of the column, but does not record the contraint name o Prevent concurrent CREATE TABLE table1 from sometimes returning a cryptic error message http://archives.postgresql.org/pgsql-bugs/2007-10/msg00169.php o Add CREATE SCHEMA ... LIKE that copies a schema o Add CREATE TABLE LIKE ... INCLUDING COMMENTS * UPDATE o Allow UPDATE tab SET ROW (col, ...) = (SELECT...) http://archives.postgresql.org/pgsql-hackers/2006-07/msg01306.php http://archives.postgresql.org/pgsql-hackers/2007-03/msg00865.php http://archives.postgresql.org/pgsql-patches/2007-04/msg00315.php http://archives.postgresql.org/pgsql-patches/2008-03/msg00237.php o Research self-referential UPDATEs that see inconsistent row versions in read-committed mode http://archives.postgresql.org/pgsql-hackers/2007-05/msg00507.php http://archives.postgresql.org/pgsql-hackers/2007-06/msg00016.php o Allow GLOBAL temporary tables to exist as empty by default in all sessions http://archives.postgresql.org/pgsql-hackers/2007-07/msg00006.php * ALTER o Have ALTER TABLE RENAME rename SERIAL sequence names http://archives.postgresql.org/pgsql-hackers/2008-03/msg00008.php o Have ALTER SEQUENCE RENAME rename the sequence name stored in the sequence table http://archives.postgresql.org/pgsql-bugs/2007-09/msg00092.php http://archives.postgresql.org/pgsql-bugs/2007-10/msg00007.php http://archives.postgresql.org/pgsql-hackers/2008-03/msg00008.php o Add ALTER DOMAIN to modify the underlying data type o %Allow ALTER TABLE ... ALTER CONSTRAINT ... RENAME http://archives.postgresql.org/pgsql-patches/2006-02/msg00168.php o %Allow ALTER TABLE to change constraint deferrability and actions o Add missing object types for ALTER ... SET SCHEMA o Allow ALTER TABLESPACE to move to different directories o Allow databases to be moved to different tablespaces o Allow moving system tables to other tablespaces, where possible Currently non-global system tables must be in the default database tablespace. Global system tables can never be moved. o -Prevent parent tables from altering or dropping constraints like CHECK that are inherited by child tables unless CASCADE is used o -Prevent child tables from altering or dropping constraints like CHECK that were inherited from the parent table o Have ALTER INDEX update the name of a constraint using that index o Add ALTER TABLE RENAME CONSTRAINT, update index name also o Allow column display reordering by recording a display, storage, and permanent id for every column? http://archives.postgresql.org/pgsql-hackers/2006-12/msg00782.php o Allow an existing index to be marked as a table's primary key http://archives.postgresql.org/pgsql-hackers/2008-04/msg00500.php * CLUSTER o Automatically maintain clustering on a table This might require some background daemon to maintain clustering during periods of low usage. It might also require tables to be only partially filled for easier reorganization. Another idea would be to create a merged heap/index data file so an index lookup would automatically access the heap data too. A third idea would be to store heap rows in hashed groups, perhaps using a user-supplied hash function. http://archives.postgresql.org/pgsql-performance/2004-08/msg00349.php o %Add default clustering to system tables To do this, determine the ideal cluster index for each system table and set the cluster setting during initdb. o %Add VERBOSE option to report tables as they are processed, like VACUUM VERBOSE * COPY o Allow COPY to report error lines and continue This requires the use of a savepoint before each COPY line is processed, with ROLLBACK on COPY failure. http://archives.postgresql.org/pgsql-hackers/2007-12/msg00572.php o Allow COPY on a newly-created table to skip WAL logging On crash recovery, the table involved in the COPY would be removed or have its heap and index files truncated. One issue is that no other backend should be able to add to the table at the same time, which is something that is currently allowed. This currently is done if the table is created inside the same transaction block as the COPY because no other backends can see the table. o Consider using a ring buffer for COPY FROM http://archives.postgresql.org/pgsql-patches/2008-02/msg00140.php http://archives.postgresql.org/pgsql-hackers/2008-02/msg01080.php o Allow COPY FROM to create index entries in bulk http://archives.postgresql.org/pgsql-hackers/2008-02/msg00811.php o Allow COPY in CSV mode to control whether a quoted zero-length string is treated as NULL Currently this is always treated as a zero-length string, which generates an error when loading into an integer column http://archives.postgresql.org/pgsql-hackers/2007-07/msg00905.php o Impove COPY performance http://archives.postgresql.org/pgsql-hackers/2008-02/msg00954.php o Allow COPY to report errors sooner http://archives.postgresql.org/pgsql-hackers/2008-04/msg01169.php * GRANT/REVOKE o Allow column-level privileges o %Allow GRANT/REVOKE permissions to be applied to all schema objects with one command The proposed syntax is: GRANT SELECT ON ALL TABLES IN public TO phpuser; GRANT SELECT ON NEW TABLES IN public TO phpuser; o Allow GRANT/REVOKE permissions to be inherited by objects based on schema permissions o Allow SERIAL sequences to inherit permissions from the base table? * CURSOR o Prevent DROP TABLE from dropping a row referenced by its own open cursor? * INSERT o Allow INSERT/UPDATE of the system-generated oid value for a row o In rules, allow VALUES() to contain a mixture of 'old' and 'new' references * SHOW/SET o Add SET PERFORMANCE_TIPS option to suggest INDEX, VACUUM, VACUUM ANALYZE, and CLUSTER * LISTEN/NOTIFY o 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. o 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. o Allow multiple identical NOTIFY events to always be communicated to the client, rather than sent as a single notification to the listener http://archives.postgresql.org/pgsql-general/2008-01/msg00057.php o Allow NOTIFY in rules involving conditionals o Improve LISTEN concurrency http://archives.postgresql.org/pgsql-hackers/2008-02/msg01106.php Referential Integrity ===================== * Add MATCH PARTIAL referential integrity * Change foreign key constraint for array -> element to mean element in array? * Fix problem when cascading referential triggers make changes on cascaded tables, seeing the tables in an intermediate state http://archives.postgresql.org/pgsql-hackers/2005-09/msg00174.php http://archives.postgresql.org/pgsql-hackers/2005-09/msg00174.php * Allow DEFERRABLE and end-of-statement UNIQUE constraints? This would allow UPDATE tab SET col = col + 1 to work if col has a unique index. Currently, uniqueness checks are done while the command is being executed, rather than at the end of the statement or transaction. http://people.planetpostgresql.org/greg/index.php?/archives/2006/06/10.html http://archives.postgresql.org/pgsql-hackers/2006-09/msg01458.php * Optimize referential integrity checks http://archives.postgresql.org/pgsql-performance/2005-10/msg00458.php http://archives.postgresql.org/pgsql-hackers/2007-04/msg00744.php Server-Side Languages ===================== * PL/pgSQL o Fix RENAME to work on variables other than OLD/NEW http://archives.postgresql.org/pgsql-hackers/2002-03/msg00591.php http://archives.postgresql.org/pgsql-hackers/2007-01/msg01615.php http://archives.postgresql.org/pgsql-hackers/2007-01/msg01587.php o Allow function parameters to be passed by name, get_employee_salary(12345 AS emp_id, 2001 AS tax_year) o Allow handling of %TYPE arrays, e.g. tab.col%TYPE[] o Allow listing of record column names, and access to record columns via variables, e.g. columns := r.(*), tval2 := r.(colname) http://archives.postgresql.org/pgsql-patches/2005-07/msg00458.php http://archives.postgresql.org/pgsql-patches/2006-05/msg00302.php http://archives.postgresql.org/pgsql-patches/2006-06/msg00031.php o Add support for SCROLL cursors o Add support for WITH HOLD cursors o Allow row and record variables to be set to NULL constants, and allow NULL tests on such variables Because a row is not scalar, do not allow assignment from NULL-valued scalars. http://archives.postgresql.org/pgsql-hackers/2006-10/msg00070.php o Review handling of MOVE and FETCH http://archives.postgresql.org/pgsql-patches/2007-04/msg00527.php o Improve logic of determining if an identifier is a a variable or column name http://archives.postgresql.org/pgsql-hackers/2007-07/msg00436.php o Consider keeping seperate cached copies when search_path changes http://archives.postgresql.org/pgsql-hackers/2008-01/msg01009.php o -Add CASE capability to language (already in SQL) http://archives.postgresql.org/pgsql-hackers/2008-01/msg00696.php * Other o Add table function support to pltcl, plpythonu o Add support for polymorphic arguments and return types to languages other than PL/PgSQL o Add capability to create and call PROCEDURES o Add support for OUT and INOUT parameters to languages other than PL/PgSQL o Add PL/PythonU tracebacks http://archives.postgresql.org/pgsql-patches/2006-02/msg00288.php o Allow data to be passed in native language formats, rather than only text http://archives.postgresql.org/pgsql-hackers/2007-05/msg00289.php o Add ability to obfuscate function bodies http://archives.postgresql.org/pgsql-patches/2008-01/msg00125.php Clients ======= * Have pg_ctl look at PGHOST in case it is a socket directory? * Allow pg_ctl to work properly with configuration files located outside the PGDATA directory pg_ctl can not read the pid file because it isn't located in the config directory but in the PGDATA directory. The solution is to allow pg_ctl to read and understand postgresql.conf to find the data_directory value. * Add a function like pg_get_indexdef() that report more detailed index information http://archives.postgresql.org/pgsql-bugs/2007-12/msg00166.php * psql o -Have psql show current values for a sequence o 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. http://archives.postgresql.org/pgsql-hackers/2004-01/msg00191.php o Make psql's \d commands more consistent http://archives.postgresql.org/pgsql-hackers/2004-11/msg00014.php http://archives.postgresql.org/pgsql-hackers/2004-11/msg00014.php o Consistently display privilege information for all objects in psql o Add auto-expanded mode so expanded output is used if the row length is wider than the screen width. Consider using auto-expanded mode for backslash commands like \df+. o Prevent tab completion of SET TRANSACTION from querying the database and therefore preventing the transaction isolation level from being set. Currently SET causes a database lookup to check all supported session variables. This query causes problems because setting the transaction isolation level must be the first statement of a transaction. o Add a \set variable to control whether \s displays line numbers Another option is to add \# which lists line numbers, and allows command execution. http://archives.postgresql.org/pgsql-hackers/2006-12/msg00255.php o Prevent escape string warnings when object names have backslashes http://archives.postgresql.org/pgsql-hackers/2008-01/msg00227.php o Have \d show foreign keys that reference a table's primary key http://archives.postgresql.org/pgsql-hackers/2007-04/msg00424.php o Have \d show child tables that inherit from the specified parent o -Have \l+ show database size, if permissions allow Ideally it will not generate an error for invalid permissions o Include the symbolic SQLSTATE name in verbose error reports http://archives.postgresql.org/pgsql-general/2007-09/msg00438.php o -Improve display of enums to show valid enum values o Add prompt escape to display the client and server versions o 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. http://archives.postgresql.org/pgsql-hackers/2008-05/msg00404.php http://www.w3.org/TR/CSS21/tables.html#auto-table-layout o Add "auto" expanded mode that outputs in expanded format if "wrapped" mode can't wrap the output to the screen width http://archives.postgresql.org/pgsql-hackers/2008-05/msg00417.php * pg_dump / pg_restore o %Add dumping of comments on index columns and composite type columns o %Add full object name to the tag field. eg. for operators we need '=(integer, integer)', instead of just '='. o Add pg_dumpall custom format dumps? o Allow selection of individual object(s) of all types, not just tables o In a selective dump, allow dumping of an object and all its dependencies o Add options like pg_restore -l and -L to pg_dump o Stop dumping CASCADE on DROP TYPE commands in clean mode o Allow pg_dump --clean to drop roles that own objects or have privileges o Change pg_dump so that a comment on the dumped database is applied to the loaded database, even if the database has a different name. This will require new backend syntax, perhaps COMMENT ON CURRENT DATABASE. o Remove unnecessary function pointer abstractions in pg_dump source code o Allow pg_dump to utilize multiple CPUs and I/O channels by dumping multiple objects simultaneously The difficulty with this is getting multiple dump processes to produce a single dump output file. It also would require several sessions to share the same snapshot. http://archives.postgresql.org/pgsql-hackers/2008-02/msg00205.php o Allow pg_restore to utilize multiple CPUs and I/O channels by restoring multiple objects simultaneously This might require a pg_restore flag to indicate how many simultaneous operations should be performed. Only pg_dump's -Fc format has the necessary dependency information. http://archives.postgresql.org/pgsql-hackers/2008-02/msg00963.php o To better utilize resources, allow pg_restore to check foreign keys simultaneously, where possible o Allow pg_restore to create all indexes of a table concurrently, via a single heap scan This requires a pg_dump -Fc file because that format contains the required dependency information. http://archives.postgresql.org/pgsql-general/2007-05/msg01274.php o Allow pg_restore to load different parts of the COPY data simultaneously o -Prevent pg_dump/pg_restore from being affected by statement_timeout Using psql to restore a pg_dump dump is also affected. o Remove pre-7.3 pg_dump code that assumes pg_depend does not exit o Allow pre/data/post files when schema and data are dumped separately, for performance reasons http://archives.postgresql.org/pgsql-hackers/2008-02/msg00205.php * ecpg o Docs Document differences between ecpg and the SQL standard and information about the Informix-compatibility module. o Solve cardinality > 1 for input descriptors / variables? o Add a semantic check level, e.g. check if a table really exists o fix handling of DB attributes that are arrays o Use backend PREPARE/EXECUTE facility for ecpg where possible o Implement SQLDA o Fix nested C comments o %sqlwarn[6] should be 'W' if the PRECISION or SCALE value specified o Make SET CONNECTION thread-aware, non-standard? o Allow multidimensional arrays o Add internationalized message strings o Implement COPY FROM STDIN * libpq o Add PQescapeIdentifierConn() o Prevent PQfnumber() from lowercasing unquoted the column name PQfnumber() should never have been doing lowercasing, but historically it has so we need a way to prevent it o Allow statement results to be automatically batched to the client Currently all statement results are transferred to the libpq client before libpq makes the results available to the application. This feature would allow the application to make use of the first result rows while the rest are transferred, or held on the server waiting for them to be requested by libpq. One complexity is that a statement like SELECT 1/col could error out mid-way through the result set. o Consider disallowing multiple queries in PQexec() as an additional barrier to SQL injection attacks http://archives.postgresql.org/pgsql-hackers/2007-01/msg00184.php o Add PQexecf() that allows complex parameter substitution http://archives.postgresql.org/pgsql-hackers/2007-03/msg01803.php o Add SQLSTATE severity to PGconn return status http://archives.postgresql.org/pgsql-interfaces/2007-11/msg00015.php Triggers ======== * Add deferred trigger queue file Right now all deferred trigger information is stored in backend memory. This could exhaust memory for very large trigger queues. This item involves dumping large queues into files, or doing some kind of join to process all the triggers, or some bulk operation. http://archives.postgresql.org/pgsql-hackers/2008-05/msg00876.php * Allow triggers to be disabled in only the current session. This is currently possible by starting a multi-statement transaction, modifying the system tables, performing the desired SQL, restoring the system tables, and committing the transaction. ALTER TABLE ... TRIGGER requires a table lock so it is not ideal for this usage. * With disabled triggers, allow pg_dump to use ALTER TABLE ADD FOREIGN KEY If the dump is known to be valid, allow foreign keys to be added without revalidating the data. * Allow statement-level triggers to access modified rows * Support triggers on columns http://archives.postgresql.org/pgsql-patches/2005-07/msg00107.php * Allow AFTER triggers on system tables System tables are modified in many places in the backend without going through the executor and therefore not causing triggers to fire. To complete this item, the functions that modify system tables will have to fire triggers. * Tighten trigger permission checks http://archives.postgresql.org/pgsql-hackers/2006-12/msg00564.php * Allow BEFORE INSERT triggers on views http://archives.postgresql.org/pgsql-general/2007-02/msg01466.php * -Add ability to trigger on TRUNCATE * Add database and transaction-level triggers http://archives.postgresql.org/pgsql-hackers/2008-03/msg00451.php http://archives.postgresql.org/pgsql-hackers/2008-05/msg00620.php * Reduce locking requirements for creating a trigger http://archives.postgresql.org/pgsql-hackers/2008-06/msg00635.php Indexes ======= * Add UNIQUE capability to non-btree indexes * Prevent index uniqueness checks when UPDATE does not modify the column Uniqueness (index) checks are done when updating a column even if the column is not modified by the UPDATE. * Allow the creation of on-disk bitmap indexes which can be quickly combined with other bitmap indexes Such indexes could be more compact if there are only a few distinct values. Such indexes can also be compressed. Keeping such indexes updated can be costly. http://archives.postgresql.org/pgsql-patches/2005-07/msg00512.php http://archives.postgresql.org/pgsql-hackers/2006-12/msg01107.php http://archives.postgresql.org/pgsql-hackers/2007-03/msg00265.php http://archives.postgresql.org/pgsql-hackers/2007-03/msg01214.php http://archives.postgresql.org/pgsql-patches/2007-05/msg00013.php http://archives.postgresql.org/pgsql-hackers/2007-07/msg00741.php * Allow accurate statistics to be collected on indexes with more than one column or expression indexes, perhaps using per-index statistics http://archives.postgresql.org/pgsql-performance/2006-10/msg00222.php http://archives.postgresql.org/pgsql-hackers/2007-03/msg01131.php * Consider increasing the default and maximum number of statistics targets, and reduce statistics target overhead Also consider having a larger statistics target for indexed columns and expression indexes. http://archives.postgresql.org/pgsql-general/2007-05/msg01228.php http://archives.postgresql.org/pgsql-general/2007-06/msg00542.php http://archives.postgresql.org/pgsql-hackers/2008-01/msg01066.php http://archives.postgresql.org/pgsql-hackers/2008-03/msg00188.php * 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. http://archives.postgresql.org/pgsql-hackers/2006-12/msg00341.php http://archives.postgresql.org/pgsql-hackers/2007-02/msg01264.php http://archives.postgresql.org/pgsql-hackers/2007-03/msg00465.php http://archives.postgresql.org/pgsql-patches/2007-03/msg00163.php http://archives.postgresql.org/pgsql-hackers/2007-08/msg00014.php http://archives.postgresql.org/pgsql-hackers/2007-08/msg00487.php http://archives.postgresql.org/pgsql-hackers/2008-04/msg01589.php * Add REINDEX CONCURRENTLY, like CREATE INDEX CONCURRENTLY This is difficult because you must upgrade to an exclusive table lock to replace the existing index file. CREATE INDEX CONCURRENTLY does not have this complication. This would allow index compaction without downtime. http://archives.postgresql.org/pgsql-performance/2007-08/msg00289.php * Allow multiple indexes to be created concurrently, ideally via a single heap scan, and have pg_restore use it * Consider sorting entries before inserting into btree index http://archives.postgresql.org/pgsql-general/2008-01/msg01010.php * Allow index scans to return matching index keys, not just the matching heap locations http://archives.postgresql.org/pgsql-hackers/2008-04/msg01657.php * Inheritance o Allow inherited tables to inherit indexes, UNIQUE constraints, and primary/foreign keys o Honor UNIQUE INDEX on base column in INSERTs/UPDATEs on inherited table, e.g. INSERT INTO inherit_table (unique_index_col) VALUES (dup) should fail The main difficulty with this item is the problem of creating an index that can span multiple tables. o Allow SELECT ... FOR UPDATE on inherited tables o Require all CHECK constraints to be inherited http://archives.postgresql.org/pgsql-bugs/2007-04/msg00026.php o Add checks to prevent a CREATE RULE views on inherited tables http://archives.postgresql.org/pgsql-general/2008-02/msg01420.php http://archives.postgresql.org/pgsql-general/2008-03/msg00077.php * GIST o Add more GIST index support for geometric data types o Allow GIST indexes to create certain complex index types, like digital trees (see Aoki) * Hash http://archives.postgresql.org/pgsql-hackers/2007-09/msg00051.php o Pack hash index buckets onto disk pages more efficiently Currently only one hash bucket can be stored on a page. Ideally several hash buckets could be stored on a single page and greater granularity used for the hash algorithm. http://archives.postgresql.org/pgsql-hackers/2004-06/msg00168.php o Consider sorting hash buckets so entries can be found using a binary search, rather than a linear scan o In hash indexes, consider storing the hash value with or instead of the key itself o Add WAL logging for crash recovery o Allow multi-column hash indexes o -During index creation, pre-sort the tuples to improve build speed Sorting ======= * Consider using hash buckets to do DISTINCT, rather than sorting This would be beneficial when there are few distinct values. This is already used by GROUP BY. * Consider whether duplicate keys should be sorted by block/offset http://archives.postgresql.org/pgsql-hackers/2008-03/msg00558.php * -Avoid tuple some tuple copying in sort routines * Consider being smarter about memory and external files used during sorts http://archives.postgresql.org/pgsql-hackers/2007-11/msg01101.php http://archives.postgresql.org/pgsql-hackers/2007-12/msg00045.php * Consider detoasting keys before sorting Fsync ===== * Determine optimal fdatasync/fsync, O_SYNC/O_DSYNC options Ideally this requires a separate test program that can be run at initdb time or optionally later. Consider O_SYNC when O_DIRECT exists. * Add program to test if fsync has a delay compared to non-fsync * Consider sorting writes during checkpoint http://archives.postgresql.org/pgsql-hackers/2007-06/msg00541.php Cache Usage =========== * Speed up COUNT(*) We could use a fixed row count and a +/- count to follow MVCC visibility rules, or a single cached value could be used and invalidated if anyone modifies the table. Another idea is to get a count directly from a unique index, but for this to be faster than a sequential scan it must avoid access to the heap to obtain tuple visibility information. * Provide a way to calculate an "estimated COUNT(*)" Perhaps by using the optimizer's cardinality estimates or random sampling. http://archives.postgresql.org/pgsql-hackers/2005-11/msg00943.php * Allow data to be pulled directly from indexes Currently indexes do not have enough tuple visibility information to allow data to be pulled from the index without also accessing the heap. One way to allow this is to set a bit on index tuples to indicate if a tuple is currently visible to all transactions when the first valid heap lookup happens. This bit would have to be cleared when a heap tuple is expired. Another idea is to maintain a bitmap of heap pages where all rows are visible to all backends, and allow index lookups to reference that bitmap to avoid heap lookups, perhaps the same bitmap we might add someday to determine which heap pages need vacuuming. Frequently accessed bitmaps would have to be stored in shared memory. One 8k page of bitmaps could track 512MB of heap pages. A third idea would be for a heap scan to check if all rows are visible and if so set a per-table flag which can be checked by index scans. Any change to the table would have to clear the flag. To detect changes during the heap scan a counter could be set at the start and checked at the end --- if it is the same, the table has not been modified --- any table change would increment the counter. http://archives.postgresql.org/pgsql-patches/2007-10/msg00166.php http://archives.postgresql.org/pgsql-patches/2008-01/msg00049.php * Consider automatic caching of statements at various levels: o Parsed query tree o Query execute plan o Query results http://archives.postgresql.org/pgsql-hackers/2008-04/msg00823.php * Consider increasing internal areas when shared buffers is increased http://archives.postgresql.org/pgsql-hackers/2005-10/msg01419.php * Consider decreasing the amount of memory used by PrivateRefCount http://archives.postgresql.org/pgsql-hackers/2006-11/msg00797.php http://archives.postgresql.org/pgsql-hackers/2007-01/msg00752.php * Consider allowing higher priority queries to have referenced buffer cache pages stay in memory longer http://archives.postgresql.org/pgsql-hackers/2007-11/msg00562.php Vacuum ====== * Improve speed with indexes For large table adjustments during VACUUM FULL, it is faster to cluster or reindex rather than update the index. Also, index updates can bloat the index. http://archives.postgresql.org/pgsql-hackers/2007-03/msg00024.php http://archives.postgresql.org/pgsql-performance/2007-05/msg00296.php http://archives.postgresql.org/pgsql-hackers/2007-08/msg00307.php * Auto-fill the free space map by scanning the buffer cache or by checking pages written by the background writer http://archives.postgresql.org/pgsql-hackers/2006-02/msg01125.php http://archives.postgresql.org/pgsql-hackers/2006-03/msg00011.php * Create a bitmap of pages that need vacuuming Instead of sequentially scanning the entire table, have the background writer or some other process record pages that have expired rows, then VACUUM can look at just those pages rather than the entire table. In the event of a system crash, the bitmap would probably be invalidated. One complexity is that index entries still have to be vacuumed, and doing this without an index scan (by using the heap values to find the index entry) might be slow and unreliable, especially for user-defined index functions. http://archives.postgresql.org/pgsql-hackers/2006-12/msg01188.php http://archives.postgresql.org/pgsql-hackers/2007-01/msg00121.php http://archives.postgresql.org/pgsql-patches/2007-03/msg00508.php http://archives.postgresql.org/pgsql-patches/2007-04/msg00347.php http://archives.postgresql.org/pgsql-hackers/2007-11/msg00156.php http://archives.postgresql.org/pgsql-hackers/2008-03/msg00546.php http://archives.postgresql.org/pgsql-hackers/2008-04/msg00416.php * Allow FSM to return free space toward the beginning of the heap file, in hopes that empty pages at the end can be truncated by VACUUM * Allow FSM page return free space based on table clustering, to assist in maintaining clustering? * -Improve dead row detection during multi-statement transactions usage http://archives.postgresql.org/pgsql-patches/2007-03/msg00358.php * Consider a more compact data representation for dead tuples http://archives.postgresql.org/pgsql-patches/2007-05/msg00143.php * Auto-vacuum o %Issue log message to suggest VACUUM FULL if a table is nearly empty? o Improve control of auto-vacuum http://archives.postgresql.org/pgsql-hackers/2006-12/msg00876.php o Prevent long-lived temporary tables from causing frozen-xid advancement starvation The problem is that autovacuum cannot vacuum them to set frozen xids; only the session that created them can do that. http://archives.postgresql.org/pgsql-general/2007-06/msg01645.php o Store per-table autovacuum settings in pg_class.reloptions. http://archives.postgresql.org/pgsql-hackers/2007-02/msg01440.php http://archives.postgresql.org/pgsql-hackers/2008-01/msg00724.php o Prevent autovacuum from running if an old transaction is still running from the last vacuum http://archives.postgresql.org/pgsql-hackers/2007-11/msg00899.php Locking ======= * Fix priority ordering of read and write light-weight locks (Neil) http://archives.postgresql.org/pgsql-hackers/2004-11/msg00893.php http://archives.postgresql.org/pgsql-hackers/2004-11/msg00905.php * Fix problem when multiple subtransactions of the same outer transaction hold different types of locks, and one subtransaction aborts http://archives.postgresql.org/pgsql-hackers/2006-11/msg01011.php http://archives.postgresql.org/pgsql-hackers/2006-12/msg00001.php http://archives.postgresql.org/pgsql-hackers/2007-02/msg00435.php http://archives.postgresql.org/pgsql-hackers/2007-05/msg00773.php * Allow UPDATEs on only non-referential integrity columns not to conflict with referential integrity locks http://archives.postgresql.org/pgsql-hackers/2007-02/msg00073.php * Add idle_in_transaction_timeout GUC so locks are not held for long periods of time * Improve deadlock detection when a page cleaning lock conflicts with a shared buffer that is pinned http://archives.postgresql.org/pgsql-bugs/2008-01/msg00138.php http://archives.postgresql.org/pgsql-hackers/2008-01/msg00873.php http://archives.postgresql.org/pgsql-committers/2008-01/msg00365.php * Detect deadlocks involving LockBufferForCleanup() http://archives.postgresql.org/pgsql-hackers/2008-01/msg00873.php 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. 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. http://archives.postgresql.org/pgsql-hackers/2002-06/msg00655.php o When off, write CRC to WAL and check file system blocks on recovery If CRC check fails during recovery, remember the page in case a later CRC for that page properly matches. o Write full pages during file system write and not when the page is modified in the buffer cache This allows most full page writes to happen in the background writer. It might cause problems for applying WAL on recovery into a partially-written page, but later the full page will be replaced from WAL. * Allow WAL traffic to be streamed to another server for stand-by replication * Reduce WAL traffic so only modified values are written rather than entire rows http://archives.postgresql.org/pgsql-hackers/2007-03/msg01589.php * Allow WAL information to recover corrupted pg_controldata http://archives.postgresql.org/pgsql-patches/2006-06/msg00025.php * Find a way to reduce rotational delay when repeatedly writing last WAL page Currently fsync of WAL requires the disk platter to perform a full rotation to fsync again. One idea is to write the WAL to different offsets that might reduce the rotational delay. http://archives.postgresql.org/pgsql-hackers/2002-11/msg00483.php * 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. http://archives.postgresql.org/pgsql-hackers/2005-12/msg01016.php * 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. http://archives.postgresql.org/pgsql-hackers/2005-12/msg01016.php * Speed WAL recovery by allowing more than one page to be prefetched This should be done utilizing the same infrastructure used for prefetching in general to avoid introducing complex error-prone code in WAL replay. http://archives.postgresql.org/pgsql-general/2007-12/msg00683.php http://archives.postgresql.org/pgsql-hackers/2007-12/msg00497.php http://archives.postgresql.org/pgsql-hackers/2008-02/msg01279.php * Improve WAL concurrency by increasing lock granularity http://archives.postgresql.org/pgsql-hackers/2008-02/msg00556.php * Be more aggressive about creating WAL files http://archives.postgresql.org/pgsql-hackers/2007-10/msg01325.php http://archives.postgresql.org/pgsql-hackers/2004-07/msg01075.php http://archives.postgresql.org/pgsql-hackers/2005-04/msg00556.php * Have resource managers report the duration of their status changes http://archives.postgresql.org/pgsql-hackers/2007-10/msg01468.php * Move pgfoundry's xlogdump to /contrib and have it rely more closely on the WAL backend code http://archives.postgresql.org/pgsql-hackers/2007-11/msg00035.php Optimizer / Executor ==================== * Improve selectivity functions for geometric operators * Precompile SQL functions to avoid overhead * Create utility to compute accurate random_page_cost value * Improve ability to display optimizer analysis using OPTIMIZER_DEBUG * Have EXPLAIN ANALYZE issue NOTICE messages when the estimated and actual row counts differ by a specified percentage * Improve how ANALYZE computes in-doubt tuples http://archives.postgresql.org/pgsql-hackers/2007-11/msg00771.php * Log statements where the optimizer row estimates were dramatically different from the number of rows actually found? * Consider compressed annealing to search for query plans This might replace GEQO, http://sixdemonbag.org/Djinni. * Improve merge join performance by allowing mark/restore of tuple sources http://archives.postgresql.org/pgsql-hackers/2007-01/msg00096.php * Consider using a hash for joining to a large IN (VALUES ...) list http://archives.postgresql.org/pgsql-hackers/2007-05/msg00450.php Background Writer ================= * Consider having the background writer update the transaction status hint bits before writing out the page Implementing this requires the background writer to have access to system catalogs and the transaction status log. * Consider adding buffers the background writer finds reusable to the free list http://archives.postgresql.org/pgsql-hackers/2007-04/msg00781.php * Automatically tune bgwriter_delay based on activity rather then using a fixed interval http://archives.postgresql.org/pgsql-hackers/2007-04/msg00781.php * Consider wither increasing BM_MAX_USAGE_COUNT improves performance http://archives.postgresql.org/pgsql-hackers/2007-06/msg01007.php * Test to see if calling PreallocXlogFiles() from the background writer will help with WAL segment creation latency http://archives.postgresql.org/pgsql-patches/2007-06/msg00340.php Miscellaneous Performance ========================= * Do async I/O for faster random read-ahead of data Async I/O allows multiple I/O requests to be sent to the disk with results coming back asynchronously. http://archives.postgresql.org/pgsql-hackers/2006-10/msg00820.php http://archives.postgresql.org/pgsql-performance/2007-09/msg00255.php http://archives.postgresql.org/pgsql-hackers/2007-12/msg00027.php http://archives.postgresql.org/pgsql-patches/2008-01/msg00170.php * Use mmap() rather than SYSV shared memory or to write WAL files? This would remove the requirement for SYSV SHM but would introduce portability issues. Anonymous mmap (or mmap to /dev/zero) is required to prevent I/O overhead. * Consider mmap()'ing files into a backend? Doing I/O to large tables would consume a lot of address space or require frequent mapping/unmapping. Extending the file also causes mapping problems that might require mapping only individual pages, leading to thousands of mappings. Another problem is that there is no way to _prevent_ I/O to disk from the dirty shared buffers so changes could hit disk before WAL is written. * Add a script to ask system configuration questions and tune postgresql.conf * Consider ways of storing rows more compactly on disk o Reduce the row header size? o Consider reducing on-disk varlena length from four bytes to two because a heap row cannot be more than 64k in length * Consider increasing NUM_CLOG_BUFFERS http://archives.postgresql.org/pgsql-hackers/2007-08/msg00030.php http://archives.postgresql.org/pgsql-performance/2007-08/msg00024.php * Consider transaction start/end performance improvements http://archives.postgresql.org/pgsql-hackers/2007-07/msg00948.php http://archives.postgresql.org/pgsql-hackers/2008-03/msg00361.php * Allow user configuration of TOAST thresholds http://archives.postgresql.org/pgsql-hackers/2007-02/msg00213.php http://archives.postgresql.org/pgsql-hackers/2007-08/msg00082.php * Allow configuration of backend priorities via the operating system Though backend priorities make priority inversion during lock waits possible, research shows that this is not a huge problem. http://archives.postgresql.org/pgsql-general/2007-02/msg00493.php * Experiment with multi-threaded backend better I/O utilization This would allow a single query to make use of multiple I/O channels simultaneously. One idea is to create a background reader that can pre-fetch sequential and index scan pages needed by other backends. This could be expanded to allow concurrent reads from multiple devices in a partitioned table. * Experiment with multi-threaded backend better CPU utilization This would allow several CPUs to be used for a single query, such as for sorting or query execution. * Consider increasing the minimum allowed number of shared buffers http://archives.postgresql.org/pgsql-bugs/2008-02/msg00157.php * Expire published xmin for read-only and idle transactions http://archives.postgresql.org/pgsql-hackers/2007-09/msg00343.php * Consider if CommandCounterIncrement() can avoid its AcceptInvalidationMessages() call http://archives.postgresql.org/pgsql-committers/2007-11/msg00585.php * Improve performance of shared invalidation queue for multiple CPUs http://archives.postgresql.org/pgsql-performance/2008-01/msg00023.php * Consider Cartesian joins when both relations are needed to form an indexscan qualification for a third relation http://archives.postgresql.org/pgsql-performance/2007-12/msg00090.php * Consider not storing a NULL bitmap on disk if all the NULLs are trailing http://archives.postgresql.org/pgsql-hackers/2007-12/msg00624.php http://archives.postgresql.org/pgsql-patches/2007-12/msg00109.php * Sort large UPDATE/DELETEs so it is done in heap order http://archives.postgresql.org/pgsql-hackers/2008-01/msg01119.php * SMP scalability improvements http://archives.postgresql.org/pgsql-hackers/2007-07/msg00439.php http://archives.postgresql.org/pgsql-hackers/2007-09/msg00206.php http://archives.postgresql.org/pgsql-hackers/2008-03/msg00361.php * Research reducing deTOASTing in more places http://archives.postgresql.org/pgsql-hackers/2007-09/msg00895.php * Allow one transaction to see tuples using the snapshot of another transaction This would assist multiple backends in working together. http://archives.postgresql.org/pgsql-hackers/2008-01/msg00400.php * Consider decreasing the I/O caused by updating tuple hint bits http://archives.postgresql.org/pgsql-hackers/2008-05/msg00847.php http://archives.postgresql.org/pgsql-patches/2008-07/msg00199.php Source Code =========== * Add use of 'const' for variables in source tree * Move some things from contrib into main tree * %Remove warnings created by -Wcast-align * Move platform-specific ps status display info from ps_status.c to ports * Add optional CRC checksum to heap and index pages * Improve documentation to build only interfaces (Marc) * Remove or relicense modules that are not under the BSD license, if possible * Acquire lock on a relation before building a relcache entry for it * Allow cross-compiling by generating the zic database on the target system * Improve NLS maintenance of libpgport messages linked onto applications * Clean up casting in contrib/isn http://archives.postgresql.org/pgsql-hackers/2006-11/msg00245.php * Improve the /contrib installation experience http://archives.postgresql.org/pgsql-hackers/2008-04/msg00132.php * Use UTF8 encoding for NLS messages so all server encodings can read them properly * Update Bonjour to work with newer cross-platform SDK http://archives.postgresql.org/pgsql-hackers/2006-09/msg02238.php http://archives.postgresql.org/pgsql-patches/2006-10/msg00048.php * Consider GnuTLS if OpenSSL license becomes a problem http://archives.postgresql.org/pgsql-patches/2006-05/msg00040.php http://archives.postgresql.org/pgsql-hackers/2006-12/msg01213.php * Consider changing documentation format from SGML to XML http://archives.postgresql.org/pgsql-docs/2006-12/msg00152.php * Consider making NAMEDATALEN more configurable in future releases * Update our code to handle 64-bit timezone files to match the zic source code, which now uses them * Have configure choose integer datetimes by default http://archives.postgresql.org/pgsql-patches/2007-05/msg00046.php * Support scoped IPv6 addresses http://archives.postgresql.org/pgsql-bugs/2007-05/msg00111.php * Consider allowing 64-bit integers and floats to be passed by value on 64-bit platforms Also change 32-bit floats (float4) to be passed by value at the same time. * Research use of signals and sleep wake ups http://archives.postgresql.org/pgsql-hackers/2007-07/msg00003.php * Add automated check for invalid C++ source code constructs http://archives.postgresql.org/pgsql-patches/2007-07/msg00056.php * Consider simplifying how memory context resets handle child contexts http://archives.postgresql.org/pgsql-patches/2007-08/msg00067.php * Remove use of MAKE_PTR and MAKE_OFFSET macros http://archives.postgresql.org/pgsql-general/2007-08/msg01510.php * Convert single quotes to apostrophes in the PDF documentation http://archives.postgresql.org/pgsql-docs/2007-12/msg00059.php * Create three versions of libpgport to simplify client code http://archives.postgresql.org/pgsql-hackers/2007-10/msg00154.php * Remove old-style routines for manipulating tuples http://archives.postgresql.org/pgsql-hackers/2007-10/msg00851.php * Improve detection of shared memory segments being used by others by checking the SysV shared memory field 'nattch' http://archives.postgresql.org/pgsql-hackers/2008-01/msg00656.php http://archives.postgresql.org/pgsql-hackers/2008-01/msg00673.php * Implement the non-threaded Avahi service discovery protocol http://archives.postgresql.org/pgsql-hackers/2008-02/msg00939.php http://archives.postgresql.org/pgsql-patches/2008-02/msg00097.php http://archives.postgresql.org/pgsql-hackers/2008-03/msg01211.php http://archives.postgresql.org/pgsql-patches/2008-04/msg00001.php * Implement a module capability for loading /contrib-style extensions http://archives.postgresql.org/pgsql-patches/2008-04/msg00164.php * Fix system views like pg_stat_all_tables to use set-returning functions, rather than views of per-column functions * Allow table and index WITH options to be specified via hooks, for use with plugins like GiST index methods * Win32 o Remove configure.in check for link failure when cause is found o Remove readdir() errno patch when runtime/mingwex/dirent.c rev 1.4 is released o -Remove psql newline patch when we find out why mingw outputs an extra newline o Allow psql to use readline once non-US code pages work with backslashes o Fix problem with shared memory on the Win32 Terminal Server o Diagnose problem where shared memory can sometimes not be attached by postmaster children http://archives.postgresql.org/pgsql-general/2007-08/msg01377.php o Improve signal handling http://archives.postgresql.org/pgsql-patches/2005-06/msg00027.php o Convert MSVC build system to remove most batch files http://archives.postgresql.org/pgsql-hackers/2007-08/msg00961.php o Prevent SSL from sending network packets to avoid interference with Win32 signal emulation http://archives.postgresql.org/pgsql-hackers/2007-12/msg00455.php o Support pgxs when using MSVC o Fix MSVC NLS support, like for to_char() http://archives.postgresql.org/pgsql-hackers/2008-02/msg00485.php http://archives.postgresql.org/pgsql-patches/2008-02/msg00038.php o Find a correct rint() substitute on Windows http://archives.postgresql.org/pgsql-hackers/2008-01/msg00808.php * Wire Protocol Changes o Allow dynamic character set handling o Add decoded type, length, precision o Use compression? o Update clients to use data types, typmod, schema.table.column names of result sets using new statement protocol Exotic Features =============== * Add pre-parsing phase that converts non-ISO syntax to supported syntax This could allow SQL written for other databases to run without modification. * Allow plug-in modules to emulate features from other databases * Add features of Oracle-style packages (Pavel) A package would be a schema with session-local variables, public/private functions, and initialization functions. It is also possible to implement these capabilities in any schema and not use a separate "packages" syntax at all. http://archives.postgresql.org/pgsql-hackers/2006-08/msg00384.php * Consider allowing control of upper/lower case folding of unquoted identifiers http://archives.postgresql.org/pgsql-hackers/2004-04/msg00818.php http://archives.postgresql.org/pgsql-hackers/2006-10/msg01527.php http://archives.postgresql.org/pgsql-hackers/2008-03/msg00849.php http://archives.postgresql.org/pgsql-hackers/2008-07/msg00415.php * Add autonomous transactions http://archives.postgresql.org/pgsql-hackers/2008-01/msg00893.php Features We Do _Not_ Want ========================= * All backends running as threads in a single process (not wanted) This eliminates the process protection we get from the current setup. Thread creation is usually the same overhead as process creation on modern systems, so it seems unwise to use a pure threaded model. * Optimizer hints (not wanted) Optimizer hints are used to work around problems in the optimizer. We would rather have the problems reported and fixed. http://archives.postgresql.org/pgsql-hackers/2006-08/msg00506.php http://archives.postgresql.org/pgsql-hackers/2006-10/msg00517.php http://archives.postgresql.org/pgsql-hackers/2006-10/msg00663.php Because we support postfix operators, it isn't possible to make AS optional and continue to use bison. http://archives.postgresql.org/pgsql-hackers/2003-04/msg00436.php http://archives.postgresql.org/pgsql-sql/2006-08/msg00164.php * Embedded server (not wanted) While PostgreSQL clients runs fine in limited-resource environments, the server requires multiple processes and a stable pool of resources to run reliabily and efficiently. Stripping down the PostgreSQL server to run in the same process address space as the client application would add too much complexity and failure cases.