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Diffstat (limited to 'doc/TODO')
| -rw-r--r-- | doc/TODO | 484 |
1 files changed, 254 insertions, 230 deletions
@@ -2,7 +2,7 @@ PostgreSQL TODO List ==================== Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us) -Last updated: Mon Jul 4 08:32:37 EDT 2005 +Last updated: Mon Jul 4 13:00:23 EDT 2005 The most recent version of this document can be viewed at http://www.postgresql.org/docs/faqs.TODO.html. @@ -22,12 +22,6 @@ Administration * Remove behavior of postmaster -o after making postmaster/postgres flags unique * Allow limits on per-db/role connections -* Allow server log information to be output as INSERT statements - - This would allow server log information to be easily loaded into - a database for analysis. - -* Prevent dropping user that still owns objects, or auto-drop the objects * Allow pooled connections to list all prepared queries This would allow an application inheriting a pooled connection to know @@ -35,109 +29,119 @@ Administration * Allow major upgrades without dump/reload, perhaps using pg_upgrade [pg_upgrade] -* Allow GRANT/REVOKE permissions to be applied to all schema objects with one - command - - The proposed syntax is: - GRANT SELECT ON ALL TABLES IN public TO phpuser; - GRANT SELECT ON NEW TABLES IN public TO phpuser; - -* Allow GRANT/REVOKE permissions to be inherited by objects based on - schema permissions * Check for unreferenced table files created by transactions that were in-progress when the server terminated abruptly -* Allow reporting of which objects are in which tablespaces +* Allow administrators to safely terminate individual sessions either + via an SQL function or SIGTERM - 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. + Currently SIGTERM of a backend can lead to lock table corruption. -* 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 +* Prevent dropping user that still owns objects, or auto-drop the objects +* Set proper permissions on non-system schemas during db creation - 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. + Currently all schemas are owned by the super-user because they are + copied from the template1 database. -* Add a GUC variable to control the tablespace for temporary objects and - sort files +* -Add the client IP address and port to pg_stat_activity +* Support table partitioning that allows a single table to be stored + in subtables that are partitioned based on the primary key or a WHERE + clause - It could start with a random tablespace from a supplied list and cycle - through the list. -* Add ability to monitor the use of temporary sort files -* Allow WAL replay of CREATE TABLESPACE to work when the directory - structure on the recovery computer is different from the original -* Add "include file" functionality in postgresql.conf -* -Add session start time and last statement time to pg_stat_activity -* Allow server logs to be remotely read using SQL commands -* Allow pg_hba.conf settings to be controlled via SQL +* Improve replication solutions + o Load balancing - This would require a new global table that is dumped to flat file for - use by the postmaster. We do a similar thing for pg_shadow currently. + You can use any of the master/slave replication servers to use a + standby server for data warehousing. To allow read/write queries to + multiple servers, you need multi-master replication like pgcluster. -* Allow administrators to safely terminate individual sessions either - via an SQL function or SIGTERM + o Allow replication over unreliable or non-persistent links - Currently SIGTERM of a backend can lead to lock table corruption. -* Un-comment all variables in postgresql.conf +* Configuration files + o Add "include file" functionality in postgresql.conf + o Allow postgresql.conf values to be set so they can not be changed + by the user + o Allow commenting of variables in postgresql.conf to restore them + to defaults + o Allow pg_hba.conf settings to be controlled via SQL - By not showing commented-out variables, we discourage people from - thinking that re-commenting a variable returns it to its default. - This has to address environment variables that are then overridden - by config file values. Another option is to allow commented values - to return to their default values. + This would require a new global table that is dumped to flat file for + use by the postmaster. We do a similar thing for pg_shadow currently. -* Allow point-in-time recovery to archive partially filled write-ahead - logs [pitr] - Currently only full WAL files are archived. This means that the most - recent transactions aren't available for recovery in case of a disk - failure. This could be triggered by a user command or a timer. +* 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 -* Automatically force archiving of partially-filled WAL files when - pg_stop_backup() is called or the server is stopped + 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. - Doing this will allow administrators to know more easily when the - archive contins all the files needed for point-in-time recovery. + * Allow reporting of which objects are in which tablespaces -* Create dump tool for write-ahead logs for use in determining - transaction id for point-in-time recovery -* Set proper permissions on non-system schemas during db creation + 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. - Currently all schemas are owned by the super-user because they are - copied from the template1 database. + o Add a GUC variable to control the tablespace for temporary objects + and sort files -* Add a function that returns the 'uptime' of the postmaster -* Allow a warm standby system to also allow read-only queries [pitr] + It could start with a random tablespace from a supplied list and + cycle through the list. - This is useful for checking PITR recovery. + o Allow WAL replay of CREATE TABLESPACE to work when the directory + structure on the recovery computer is different from the original -* Allow the PITR process to be debugged and data examined -* -Add the client IP address and port to pg_stat_activity -* Improve replication solutions - o Load balancing + o Allow per-tablespace quotas - You can use any of the master/slave replication servers to use a - standby server for data warehousing. To allow read/write queries to - multiple servers, you need multi-master replication like pgcluster. - o Allow replication over unreliable or non-persistent links +* Point-in-time Recovery (PITR) + o Allow point-in-time recovery to archive partially filled + write-ahead logs [pitr] -* Support table partitioning that allows a single table to be stored - in subtables that are partitioned based on the primary key or a WHERE - clause -* Allow postgresql.conf values to be set so they can not be changed by - the user -* Allow per-tablespace quotas + Currently only full WAL files are archived. This means that the + most recent transactions aren't available for recovery in case + of a disk failure. This could be triggered by a user command or + a timer. + + o Automatically force archiving of partially-filled WAL files when + pg_stop_backup() is called or the server is stopped + + Doing this will allow administrators to know more easily when + the archive contins all the files needed for point-in-time + recovery. + + o Create dump tool for write-ahead logs for use in determining + transaction id for point-in-time recovery + o Allow a warm standby system to also allow read-only queries + [pitr] + + This is useful for checking PITR recovery. + + o Allow the PITR process to be debugged and data examined + + +Monitoring +========== + +* Allow server log information to be output as INSERT statements + + This would allow server log information to be easily loaded into + a database for analysis. + +* Add ability to monitor the use of temporary sort files +* -Add session start time and last statement time to pg_stat_activity +* Allow server logs to be remotely read using SQL commands +* -Add a function that returns the start time of the postmaster Data Types @@ -156,25 +160,10 @@ Data Types The positive modulus result returned by NUMERICs might be considered inaccurate, in one sense. -* Add function to return compressed length of TOAST data values -* Allow INET subnet tests using non-constants to be indexed -* Add transaction_timestamp(), statement_timestamp(), clock_timestamp() - functionality - - Current CURRENT_TIMESTAMP returns the start time of the current - transaction, and gettimeofday() returns the wallclock time. This will - make time reporting more consistent and will allow reporting of - the statement start time. - * Have sequence dependency track use of DEFAULT sequences, - seqname.nextval (?) -* Disallow changing default expression of a SERIAL column (?) + seqname.nextval? +* Disallow changing default expression of a SERIAL column? * Allow infinite dates just like infinite timestamps -* Have initdb set DateStyle based on locale? -* Add pg_get_acldef(), pg_get_typedefault(), and pg_get_attrdef() -* Allow to_char() to print localized month names -* Allow functions to have a schema search path specified at creation time -* Allow substring/replace() to get/set bit values * Add a GUC variable to allow output of interval values in ISO8601 format * Fix data types where equality comparison isn't intuitive, e.g. box * Merge hardwired timezone names with the TZ database; allow either kind @@ -195,24 +184,7 @@ Data Types * Allow INET + INT4 to increment the host part of the address, or throw an error on overflow * Add 'tid != tid ' operator for use in corruption recovery -* Prevent to_char() on interval from returning meaningless values - - For example, to_char('1 month', 'mon') is meaningless. Basically, - most date-related parameters to to_char() are meaningless for - intervals because interval is not anchored to a date. -* Allow to_char() on interval values to accumulate the highest unit - requested - - 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 * Add ISO INTERVAL handling o Add support for day-time syntax, INTERVAL '1 2:03:04' DAY TO SECOND @@ -228,6 +200,7 @@ Data Types INTERVAL '11 months' AS YEAR should return one or zero o Support precision, CREATE TABLE foo (a INTERVAL MONTH(3)) + * ARRAYS o Allow NULLs in arrays o Allow MIN()/MAX() on arrays @@ -238,7 +211,7 @@ Data Types * BINARY DATA - o Improve vacuum of large objects, like /contrib/vacuumlo (?) + o Improve vacuum of large objects, like /contrib/vacuumlo? o Add security checking for large objects Currently large objects entries do not have owners. Permissions can @@ -251,6 +224,43 @@ Data Types This requires the TOAST column to be stored EXTERNAL. +Functions +========= + +* Add function to return compressed length of TOAST data values +* Allow INET subnet tests using non-constants to be indexed +* Add transaction_timestamp(), statement_timestamp(), clock_timestamp() + functionality + + Current CURRENT_TIMESTAMP returns the start time of the current + transaction, and gettimeofday() returns the wallclock time. This will + make time reporting more consistent and will allow reporting of + the statement start time. + +* Add pg_get_acldef(), pg_get_typedefault(), and pg_get_attrdef() +* Allow to_char() to print localized month names +* Allow functions to have a schema search path specified at creation time +* Allow substring/replace() to get/set bit values +* 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 + +* Prevent to_char() on interval from returning meaningless values + + For example, to_char('1 month', 'mon') is meaningless. Basically, + most date-related parameters to to_char() are meaningless for + intervals because interval is not anchored to a date. + + Multi-Language Support ====================== @@ -267,7 +277,7 @@ Multi-Language Support Right now only one encoding is allowed per database. * Support multiple simultaneous character sets, per SQL92 -* Improve UTF8 combined character handling (?) +* Improve UTF8 combined character handling? * Add octet_length_server() and octet_length_client() * Make octet_length_client() the same as octet_length()? @@ -287,87 +297,6 @@ Views / Rules * Allow RULE recompilation -Indexes -======= - -* Allow inherited tables to inherit index, UNIQUE constraint, and primary - key, foreign key -* UNIQUE INDEX on base column not honored on INSERTs/UPDATEs from - inherited table: INSERT INTO inherit_table (unique_index_col) VALUES - (dup) should fail - - The main difficulty with this item is the problem of creating an index - that can span more than one table. - -* Add UNIQUE capability to non-btree indexes -* Add more gist index support for geometric data types -* -Use indexes for MIN() and MAX() - - MIN/MAX queries can already be rewritten as SELECT col FROM tab ORDER - BY col {DESC} LIMIT 1. Completing this item involves doing this - transformation automatically. - -* -Use index to restrict rows returned by multi-key index when used with - non-consecutive keys to reduce heap accesses - - For an index on col1,col2,col3, and a WHERE clause of col1 = 5 and - col3 = 9, spin though the index checking for col1 and col3 matches, - rather than just col1; also called skip-scanning. - -* Prevent index uniqueness checks when UPDATE does not modify the column - - Uniqueness (index) checks are done when updating a column even if the - column is not modified by the UPDATE. - -* Fetch heap pages matching index entries in sequential order - - Rather than randomly accessing heap pages based on index entries, mark - heap pages needing access in a bitmap and do the lookups in sequential - order. Another method would be to sort heap ctids matching the index - before accessing the heap rows. - -* -Allow non-bitmap indexes to be combined by creating bitmaps in memory - - This feature allows separate indexes to be ANDed or ORed together. This - is particularly useful for data warehousing applications that need to - query the database in an many permutations. This feature scans an index - and creates an in-memory bitmap, and allows that bitmap to be combined - with other bitmap created in a similar way. The bitmap can either index - all TIDs, or be lossy, meaning it records just page numbers and each - page tuple has to be checked for validity in a separate pass. - -* Allow the creation of on-disk bitmap indexes which can be quickly - combined with other bitmap indexes - - Such indexes could be more compact if there are only a few distinct values. - Such indexes can also be compressed. Keeping such indexes updated can be - costly. - -* Allow use of indexes to search for NULLs - - One solution is to create a partial index on an IS NULL expression. - -* -Add concurrency to GIST -* Pack hash index buckets onto disk pages more efficiently - - Currently no only one hash bucket can be stored on a page. Ideally - several hash buckets could be stored on a single page and greater - granularity used for the hash algorithm. - -* Consider sorting hash buckets so entries can be found using a binary - search, rather than a linear scan -* In hash indexes, consider storing the hash value with or instead - of the key itself -* Allow accurate statistics to be collected on indexes with more than - one column or expression indexes, perhaps using per-index statistics -* Add fillfactor to control reserved free space during index creation -* Allow the creation of indexes with mixed ascending/descending specifiers -* -Fix incorrect rtree results due to wrong assumptions about "over" - operator semantics -* Allow GIST indexes to create certain complex index types, like digital - trees (see Aoki) - - Commands ======== @@ -375,12 +304,9 @@ Commands * Change LIMIT/OFFSET and FETCH/MOVE to use int8 * Allow CREATE TABLE AS to determine column lengths for complex expressions like SELECT col1 || col2 -* Allow UPDATE to handle complex aggregates [update] (?) -* Allow backslash handling in quoted strings to be disabled for portability - - The use of C-style backslashes (.e.g. \n, \r) in quoted strings is not - SQL-spec compliant, so allow such handling to be disabled. However, - disabling backslashes could break many third-party applications and tools. +* Allow UPDATE to handle complex aggregates [update]? +* -Add E'' escape string marker so eventually ordinary strings can treat + backslashes literally, for portability * Allow an alias to be provided for the target table in UPDATE/DELETE @@ -392,6 +318,7 @@ Commands functionality in DELETE. It's been agreed that the keyword should be USING, to avoid anything as confusing as DELETE FROM a FROM b. +* Have initdb set DateStyle based on locale? * Add CORRESPONDING BY to UNION/INTERSECT/EXCEPT * -Allow REINDEX to rebuild all database indexes * Add ROLLUP, CUBE, GROUPING SETS options to GROUP BY @@ -427,7 +354,7 @@ Commands Currently the system uses the operating system COPY command to create a new database. -* Add C code to copy directories for use in creating new databases +* Add C code on Unix to copy directories for use in creating new databases * 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 @@ -437,7 +364,6 @@ Commands allow pg_ctl to read and understand postgresql.conf to find the data_directory value. -* Allow column-level GRANT/REVOKE privileges * Add a GUC variable to warn about non-standard SQL usage in queries * Add MERGE command that does UPDATE/DELETE, or on failure, INSERT (rules, triggers?) @@ -446,7 +372,7 @@ Commands creation * Add COMMENT ON for all cluster global objects (roles, databases and tablespaces) -* Add an option to automatically use savepoints for each statement in a +* -Add an option to automatically use savepoints for each statement in a multi-statement transaction. When enabled, this would allow errors in multi-statement transactions @@ -467,6 +393,7 @@ Commands * Allow FOR UPDATE queries to do NOWAIT locks * Add GUC to issue notice about queries that use unjoined tables + * ALTER o Have ALTER TABLE RENAME rename SERIAL sequence names o Add ALTER DOMAIN TYPE @@ -509,12 +436,25 @@ Commands processed, with ROLLBACK on COPY failure. o -Allow COPY to understand \x as a hex byte - o Have COPY return the number of rows loaded/unloaded (?) + o Have COPY return the number of rows loaded/unloaded? o -Allow COPY to optionally include column headings in the first line o -Allow COPY FROM ... CSV to interpret newlines and carriage returns in data +* GRANT/REVOKE + o Allow column-level privileges + * Allow GRANT/REVOKE permissions to be applied to all schema objects with one + command + + The proposed syntax is: + GRANT SELECT ON ALL TABLES IN public TO phpuser; + GRANT SELECT ON NEW TABLES IN public TO phpuser; + + * Allow GRANT/REVOKE permissions to be inherited by objects based on + schema permissions + + * CURSOR o Allow UPDATE/DELETE WHERE CURRENT OF cursor @@ -524,7 +464,7 @@ Commands and no FOR UPDATE lock. o Prevent DROP TABLE from dropping a row referenced by its own open - cursor (?) + cursor? o Allow pooled connections to list all open WITH HOLD cursors @@ -546,7 +486,7 @@ Commands o -Have SHOW ALL show descriptions for server-side variables o Add SET PERFORMANCE_TIPS option to suggest INDEX, VACUUM, VACUUM ANALYZE, and CLUSTER - o Add SET PATH for schemas (?) + o Add SET PATH for schemas? This is basically the same as SET search_path. @@ -567,7 +507,7 @@ Commands o Allow function parameters to be passed by name, get_employee_salary(emp_id => 12345, tax_year => 2001) o Add Oracle-style packages - o Add table function support to pltcl, plperl, plpython (?) + o Add table function support to pltcl, plperl, plpython? o Allow PL/pgSQL to name columns by ordinal position, e.g. rec.(3) o -Allow PL/pgSQL EXECUTE query_var INTO record_var; o Add capability to create and call PROCEDURES @@ -581,7 +521,7 @@ Clients ======= * Add a libpq function to support Parse/DescribeStatement capability -* Prevent libpq's PQfnumber() from lowercasing the column name (?) +* Prevent libpq's PQfnumber() from lowercasing the column name? * Allow libpq to access SQLSTATE so pg_ctl can test for connection failure This would be used for checking if the server is up. @@ -597,6 +537,8 @@ Clients * Allow psql \pset boolean variables to set to fixed values, rather than toggle * Consistently display privilege information for all objects in psql * Improve psql's handling of multi-line queries + + * pg_dump o Have pg_dump use multi-statement transactions for INSERT dumps o Allow pg_dump to use multiple -t and -n switches [pg_dump] @@ -616,13 +558,14 @@ Clients o Add CSV output format o Update pg_dump and psql to use the new COPY libpq API (Christopher) + * ECPG o Docs Document differences between ecpg and the SQL standard and information about the Informix-compatibility module. - o Solve cardinality > 1 for input descriptors / variables (?) + o 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 @@ -647,8 +590,8 @@ Referential Integrity * -Implement shared row locks and use them in RI triggers * Enforce referential integrity for system tables * Change foreign key constraint for array -> element to mean element - in array (?) -* Allow DEFERRABLE UNIQUE constraints (?) + in array? +* Allow DEFERRABLE UNIQUE constraints? * Allow triggers to be disabled [trigger] Currently the only way to disable triggers is to modify the system @@ -710,8 +653,89 @@ Exotic Features o Allow nested schemas -PERFORMANCE -=========== +Indexes +======= + +* Allow inherited tables to inherit index, UNIQUE constraint, and primary + key, foreign key +* UNIQUE INDEX on base column not honored on INSERTs/UPDATEs from + inherited table: INSERT INTO inherit_table (unique_index_col) VALUES + (dup) should fail + + The main difficulty with this item is the problem of creating an index + that can span more than one table. + +* Add UNIQUE capability to non-btree indexes +* Add more GIST index support for geometric data types +* -Use indexes for MIN() and MAX() + + MIN/MAX queries can already be rewritten as SELECT col FROM tab ORDER + BY col {DESC} LIMIT 1. Completing this item involves doing this + transformation automatically. + +* -Use index to restrict rows returned by multi-key index when used with + non-consecutive keys to reduce heap accesses + + For an index on col1,col2,col3, and a WHERE clause of col1 = 5 and + col3 = 9, spin though the index checking for col1 and col3 matches, + rather than just col1; also called skip-scanning. + +* Prevent index uniqueness checks when UPDATE does not modify the column + + Uniqueness (index) checks are done when updating a column even if the + column is not modified by the UPDATE. + +* Fetch heap pages matching index entries in sequential order + + Rather than randomly accessing heap pages based on index entries, mark + heap pages needing access in a bitmap and do the lookups in sequential + order. Another method would be to sort heap ctids matching the index + before accessing the heap rows. + +* -Allow non-bitmap indexes to be combined by creating bitmaps in memory + + This feature allows separate indexes to be ANDed or ORed together. This + is particularly useful for data warehousing applications that need to + query the database in an many permutations. This feature scans an index + and creates an in-memory bitmap, and allows that bitmap to be combined + with other bitmap created in a similar way. The bitmap can either index + all TIDs, or be lossy, meaning it records just page numbers and each + page tuple has to be checked for validity in a separate pass. + +* Allow the creation of on-disk bitmap indexes which can be quickly + combined with other bitmap indexes + + Such indexes could be more compact if there are only a few distinct values. + Such indexes can also be compressed. Keeping such indexes updated can be + costly. + +* Allow use of indexes to search for NULLs + + One solution is to create a partial index on an IS NULL expression. + +* -Add concurrency to GIST +* Allow accurate statistics to be collected on indexes with more than + one column or expression indexes, perhaps using per-index statistics +* Add fillfactor to control reserved free space during index creation +* Allow the creation of indexes with mixed ascending/descending specifiers +* -Fix incorrect rtree results due to wrong assumptions about "over" + operator semantics +* Allow GIST indexes to create certain complex index types, like digital + trees (see Aoki) + + +* Hash + o Pack hash index buckets onto disk pages more efficiently + + Currently no only one hash bucket can be stored on a page. Ideally + several hash buckets could be stored on a single page and greater + granularity used for the hash algorithm. + + 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 Fsync @@ -724,8 +748,8 @@ Fsync * Add program to test if fsync has a delay compared to non-fsync -Cache -===== +Cache Usage +=========== * Allow free-behind capability for large sequential scans, perhaps using posix_fadvise() @@ -848,8 +872,8 @@ Locking * Fix priority ordering of read and write light-weight locks (Neil) -Startup Time -============ +Startup Time Improvements +========================= * Experiment with multi-threaded backend [thread] @@ -877,7 +901,7 @@ Write-Ahead Log eliminated from point-in-time archive files. * Reduce WAL traffic so only modified values are written rather than - entire rows (?) + entire rows? * Turn off full page writes if fsync is disabled If fsync is off, there is no purpose in writing full pages to WAL @@ -934,18 +958,18 @@ Optimizer / Executor * ANALYZE should record a pg_statistic entry for an all-NULL column * Log queries where the optimizer row estimates were dramatically - different from the number of rows actually found (?) + different from the number of rows actually found? -Miscellaneous -============= +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. -* Use mmap() rather than SYSV shared memory or to write WAL files (?) +* 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 |