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+"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+
+
+
PostgreSQL TODO list
+
+
+
+
TODO list for PostgreSQL
+Last updated: Mon Apr 18 08:57:57 EDT 2005
+
+
The most recent version of this document can be viewed at the PostgreSQL web
+site,
http://www.PostgreSQL.org.+
+
A hyphen, "-", marks changes that will appear in the upcoming 8.1 release.
+
+
Bracketed items, "[]", have more detail.
+
+
This list contains all known PostgreSQL bugs and feature requests. If
+you would like to work on an item, please read the Developer's FAQ
+first.
+
+
+
Remove behavior of postmaster -o after making postmaster/postgres
+ flags unique
+
Allow limits on per-db/user connections
+
Add group object ownership, so groups can rename/drop/grant on objects,
+ so we can implement roles
+
Allow server log information to be output as INSERT statements
+
This would allow server log information to be easily loaded into
+ a database for analysis.
+
+
Prevent default re-use of sysids for dropped users and groups
+
Currently, if a user is removed while he still owns objects, a new
+ user given might be given their user id and inherit the
+ previous users objects.
+
+
Prevent dropping user that still owns objects, or auto-drop the objects
+
Allow pooled connections to list all prepared queries
+
This would allow an application inheriting a pooled connection to know
+ the queries prepared in the current session.
+
+
Allow major upgrades without dump/reload, perhaps using pg_upgrade
+
Have SHOW ALL and pg_settings show descriptions for server-side variables
+
Allow GRANT/REVOKE permissions to be applied to all schema objects with one
+ command
+
The proposed syntax is:
+
GRANT SELECT ON ALL TABLES IN public TO phpuser;
+ GRANT SELECT ON NEW TABLES IN public TO phpuser;
+
+
Allow GRANT/REVOKE permissions to be inherited by objects based on
+ schema permissions
+
Remove unreferenced table files created by transactions that were
+ in-progress when the server terminated abruptly
+
Allow reporting of which objects are in which tablespaces
+
This item is difficult because a tablespace can contain objects from
+ multiple databases. There is a server-side function that returns the
+ databases which use a specific tablespace, so this requires a tool
+ that will call that function and connect to each database to find the
+ objects in each database for that tablespace.
+
+
Allow a database in tablespace t1 with tables created in tablespace t2
+ to be used as a template for a new database created with default
+ tablespace t2
+
All objects in the default database tablespace must have default tablespace
+ specifications. This is because new databases are created by copying
+ directories. If you mix default tablespace tables and tablespace-specified
+ tables in the same directory, creating a new database from such a mixed
+ directory would create a new database with tables that had incorrect
+ explicit tablespaces. To fix this would require modifying pg_class in the
+ newly copied database, which we don't currently do.
+
+
Add a GUC variable to control the tablespace for temporary objects and
+ sort files
+
It could start with a random tablespace from a supplied list and cycle
+ through the list.
+
+
Allow WAL replay of CREATE TABLESPACE to work when the directory
+ structure on the recovery computer is different from the original
+
Add "include file" functionality in postgresql.conf
+
Add session start time and last statement time to pg_stat_activity
+
Allow server logs to be remotely read using SQL commands
+
Allow pg_hba.conf settings to be controlled via SQL
+
This would require a new global table that is dumped to flat file for
+ use by the postmaster. We do a similar thing for pg_shadow currently.
+
+
Allow administrators to safely terminate individual sessions
+
Right now, SIGTERM will terminate a session, but it is treated as
+ though the postmaster has paniced and shared memory might not be
+ cleaned up properly. A new signal is needed for safe termination.
+
+
Un-comment all variables in postgresql.conf
+
By not showing commented-out variables, we discourage people from
+ thinking that re-commenting a variable returns it to its default.
+ This has to address environment variables that are then overridden
+ by config file values. Another option is to allow commented values
+ to return to their default values.
+
+
Allow point-in-time recovery to archive partially filled write-ahead
+ logs
+
Currently only full WAL files are archived. This means that the most
+ recent transactions aren't available for recovery in case of a disk
+ failure.
+
+
Force archiving of partially-full WAL files when pg_stop_backup() is
+ called or the server is stopped
+
Doing this will allow administrators to know more easily when the
+ archive contins all the files needed for point-in-time recovery.
+
+
Create dump tool for write-ahead logs for use in determining
+ transaction id for point-in-time recovery
+
Set proper permissions on non-system schemas during db creation
+
Currently all schemas are owned by the super-user because they are
+ copied from the template1 database.
+
+
Add a function that returns the 'uptime' of the postmaster
+
Allow a warm standby system to also allow read-only queries
+
This is useful for checking PITR recovery.
+
+
Allow the PITR process to be debugged and data examined
+
Add the client IP address and port to pg_stat_activity
+
Improve replication solutions
+
Load balancing
+
You can use any of the master/slave replication servers to use a
+ standby server for data warehousing. To allow read/write queries to
+ multiple servers, you need multi-master replication like pgcluster.
+
+
Allow replication over unreliable or non-persistent links
+
+
Support table partitioning that allows a single table to be stored
+ in subtables that are partitioned based on the primary key or a WHERE
+ clause
+
+
+
Remove Money type, add money formatting for decimal type
+
Change NUMERIC to enforce the maximum precision, and increase it
+
Add function to return compressed length of TOAST data values
+
Allow INET subnet tests using non-constants to be indexed
+
Add transaction_timestamp(), statement_timestamp(), clock_timestamp()
+ functionality
+
Current CURRENT_TIMESTAMP returns the start time of the current
+ transaction, and gettimeofday() returns the wallclock time. This will
+ make time reporting more consistent and will allow reporting of
+ the statement start time.
+
+
Have sequence dependency track use of DEFAULT sequences,
+ seqname.nextval (?)
+
Disallow changing default expression of a SERIAL column (?)
+
Allow infinite dates just like infinite timestamps
+
Have initdb set DateStyle based on locale?
+
Add pg_get_acldef(), pg_get_typedefault(), and pg_get_attrdef()
+
Allow to_char() to print localized month names
+
Allow functions to have a schema search path specified at creation time
+
Allow substring/replace() to get/set bit values
+
Add a GUC variable to allow output of interval values in ISO8601 format
+
Fix data types where equality comparison isn't intuitive, e.g. box
+
Merge hardwired timezone names with the TZ database; allow either kind
+ everywhere a TZ name is currently taken
+
Allow customization of the known set of TZ names (generalize the
+ present australian_timezones hack)
+
Allow TIMESTAMP WITH TIME ZONE to store the original timezone
+ information, either zone name or offset from UTC
+
If the TIMESTAMP value is stored with a time zone name, interval
+ computations should adjust based on the time zone rules, e.g. adding
+ 24 hours to a timestamp would yield a different result from adding one
+ day.
+
+
Prevent INET cast to CIDR if the unmasked bits are not zero, or
+ zero the bits
+
Prevent INET cast to CIDR from droping netmask, SELECT '1.1.1.1'::inet::cidr+
Add 'tid != tid ' operator for use in corruption recovery
+
Add ISo INTERVAL handling
+
Add support for day-time syntax, INTERVAL '1 2:03:04'
+DAY TO SECOND
+
Add support for year-month syntax, INTERVAL '50-6' YEAR TO MONTH
+
For syntax that isn't uniquely ISO or PG syntax, like '1:30' or
+ '1', treat as ISO if there is a range specification clause,
+ and as PG if there no clause is present, e.g. interpret '1:30'
+ MINUTE TO SECOND as '1 minute 30 seconds', and interpret '1:30'
+ as '1 hour, 30 minutes'
+
Interpret INTERVAL '1 year' MONTH as CAST (INTERVAL '1 year' AS
+ INTERVAL MONTH), and this should return '12 months'
+
Round or truncate values to the requested precision, e.g.
+ INTERVAL '11 months' AS YEAR should return one or zero
+
Support precision, CREATE TABLE foo (a INTERVAL MONTH(3))
+
+
ARRAYS
+
Allow NULLs in arrays
+
Allow MIN()/MAX() on arrays
+
Delay resolution of array expression's data type so assignment
+ coercion can be performed on empty array expressions
+
Modify array literal representation to handle array index lower bound
+ of other than one
+
+
BINARY DATA
+
Improve vacuum of large objects, like /contrib/vacuumlo (?)
+
Add security checking for large objects
+
Currently large objects entries do not have owners. Permissions can
+ only be set at the pg_largeobject table level.
+
+
Auto-delete large objects when referencing row is deleted
+
Allow read/write into TOAST values like large objects
+
This requires the TOAST column to be stored EXTERNAL.
+
+
+
+
+
Add NCHAR (as distinguished from ordinary varchar),
+
Allow locale to be set at database creation
+
Currently locale can only be set during initdb.
+
+
Allow encoding on a per-column basis
+
Right now only one encoding is allowed per database.
+
+
Optimize locale to have minimal performance impact when not used
+
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()?
+
+
+
Automatically create rules on views so they are updateable, per SQL99
+
We can only auto-create rules for simple views. For more complex
+ cases users will still have to write rules.
+
+
Add the functionality for WITH CHECK OPTION clause of CREATE VIEW
+
Allow NOTIFY in rules involving conditionals
+
Have views on temporary tables exist in the temporary namespace
+
Allow temporary views on non-temporary tables
+
Allow RULE recompilation
+
+
+
Allow inherited tables to inherit index, UNIQUE constraint, and primary
+ key, foreign key
+
UNIQUE INDEX on base column not honored on INSERTs/UPDATEs from
+ inherited table: INSERT INTO inherit_table (unique_index_col) VALUES
+ (dup) should fail
+
The main difficulty with this item is the problem of creating an index
+ that can span more than one table.
+
+
Add UNIQUE capability to non-btree indexes
+
Add rtree index support for line, lseg, path, point
+
-Use indexes for MIN() and MAX()
+
MIN/MAX queries can already be rewritten as SELECT col FROM tab ORDER
+ BY col {DESC} LIMIT 1. Completing this item involves doing this
+ transformation automatically.
+
+
Use index to restrict rows returned by multi-key index when used with
+ non-consecutive keys to reduce heap accesses
+
For an index on col1,col2,col3, and a WHERE clause of col1 = 5 and
+ col3 = 9, spin though the index checking for col1 and col3 matches,
+ rather than just col1; also called skip-scanning.
+
+
Prevent index uniqueness checks when UPDATE does not modify the column
+
Uniqueness (index) checks are done when updating a column even if the
+ column is not modified by the UPDATE.
+
+
Fetch heap pages matching index entries in sequential order
+
Rather than randomly accessing heap pages based on index entries, mark
+ heap pages needing access in a bitmap and do the lookups in sequential
+ order. Another method would be to sort heap ctids matching the index
+ before accessing the heap rows.
+
+
Allow non-bitmap indexes to be combined by creating bitmaps in memory
+
Bitmap indexes index single columns that can be combined with other bitmap
+ indexes to dynamically create a composite index to match a specific query.
+ Each index is a bitmap, and the bitmaps are bitwise AND'ed or OR'ed to be
+ combined. They can index by tid or can be lossy requiring a scan of the
+ heap page to find matching rows, or perhaps use a mixed solution where
+ tids are recorded for pages with only a few matches and per-page bitmaps
+ are used for more dense pages. Another idea is to use a 32-bit bitmap
+ for every page and set a bit based on the item number mod(32).
+
+
Allow the creation of on-disk bitmap indexes which can be quickly
+ combined with other bitmap indexes
+
Such indexes could be more compact if there are only a few distinct values.
+ Such indexes can also be compressed. Keeping such indexes updated can be
+ costly.
+
+
Allow use of indexes to search for NULLs
+
One solution is to create a partial index on an IS NULL expression.
+
+
Add concurrency to GIST
+
Pack hash index buckets onto disk pages more efficiently
+
Currently no only one hash bucket can be stored on a page. Ideally
+ several hash buckets could be stored on a single page and greater
+ granularity used for the hash algorithm.
+
+
Allow accurate statistics to be collected on indexes with more than
+ one column or expression indexes, perhaps using per-index statistics
+
Add fillfactor to control reserved free space during index creation
+
Allow the creation of indexes with mixed ascending/descending specifiers
+
+
+
Add BETWEEN ASYMMETRIC/SYMMETRIC
+
Change LIMIT/OFFSET and FETCH/MOVE to use int8
+
Allow CREATE TABLE AS to determine column lengths for complex
+ expressions like SELECT col1 || col2
+
Allow UPDATE to handle complex aggregates [update] (?)+
Allow backslash handling in quoted strings to be disabled for portability
+
The use of C-style backslashes (.e.g. \n, \r) in quoted strings is not
+ SQL-spec compliant, so allow such handling to be disabled. However,
+ disabling backslashes could break many third-party applications and tools.
+
+
Allow an alias to be provided for the target table in UPDATE/DELETE
+
This is not SQL-spec but many DBMSs allow it.
+
+
-Allow additional tables to be specified in DELETE for joins
+
UPDATE already allows this (UPDATE...FROM) but we need similar
+ functionality in DELETE. It's been agreed that the keyword should
+ be USING, to avoid anything as confusing as DELETE FROM a FROM b.
+
+
Add CORRESPONDING BY to UNION/INTERSECT/EXCEPT
+
Allow REINDEX to rebuild all database indexes, remove /contrib/reindex
+
Add ROLLUP, CUBE, GROUPING SETS options to GROUP BY
+
Add a schema option to createlang
+
Allow UPDATE tab SET ROW (col, ...) = (...) for updating multiple columns
+
Allow SET CONSTRAINTS to be qualified by schema/table name
+
Allow TRUNCATE ... CASCADE/RESTRICT
+
Allow PREPARE of cursors
+
Allow PREPARE to automatically determine parameter types based on the SQL
+ statement
+
Allow finer control over the caching of prepared query plans
+
Currently, queries prepared via the libpq API are planned on first
+ execute using the supplied parameters --- allow SQL PREPARE to do the
+ same. Also, allow control over replanning prepared queries either
+ manually or automatically when statistics for execute parameters
+ differ dramatically from those used during planning.
+
+
Allow LISTEN/NOTIFY to store info in memory rather than tables?
+
Currently LISTEN/NOTIFY information is stored in pg_listener. Storing
+ such information in memory would improve performance.
+
+
Dump large object comments in custom dump format
+
Add optional textual message to NOTIFY
+
This would allow an informational message to be added to the notify
+ message, perhaps indicating the row modified or other custom
+ information.
+
+
Use more reliable method for CREATE DATABASE to get a consistent copy
+ of db?
+
Currently the system uses the operating system COPY command to create
+ a new database.
+
+
Add C code to copy directories for use in creating new databases
+
Have pg_ctl look at PGHOST in case it is a socket directory?
+
Allow column-level GRANT/REVOKE privileges
+
Add a GUC variable to warn about non-standard SQL usage in queries
+
Add MERGE command that does UPDATE/DELETE, or on failure, INSERT (rules,
+ triggers?)
+
Add ON COMMIT capability to CREATE TABLE AS SELECT
+
Add NOVICE output level for helpful messages like automatic sequence/index
+ creation
+
Add COMMENT ON for all cluster global objects (users, groups, databases
+ and tablespaces)
+
Add an option to automatically use savepoints for each statement in a
+ multi-statement transaction.
+
When enabled, this would allow errors in multi-statement transactions
+ to be automatically ignored.
+
+
Make row-wise comparisons work per SQL spec
+
Add RESET CONNECTION command to reset all session state
+
This would include resetting of all variables (RESET ALL), dropping of
+ all temporary tables, removal of any NOTIFYs, cursors, prepared
+ queries(?), currval()s, etc. This could be used for connection pooling.
+ We could also change RESET ALL to have this functionality.
+
+
Allow FOR UPDATE queries to do NOWAIT locks
+
Add GUC to issue notice about queries that use unjoined tables
+
ALTER
+
Have ALTER TABLE RENAME rename SERIAL sequence names
+
Add ALTER DOMAIN TYPE
+
Allow ALTER TABLE ... ALTER CONSTRAINT ... RENAME
+
Allow ALTER TABLE to change constraint deferrability and actions
+
Disallow dropping of an inherited constraint
+
Allow objects to be moved to different schemas
+
Allow ALTER TABLESPACE to move to different directories
+
Allow databases and schemas to be moved to different tablespaces
+
One complexity is whether moving a schema should move all existing
+ schema objects or just define the location for future object creation.
+
+
Allow moving system tables to other tablespaces, where possible
+
Currently non-global system tables must be in the default database
+ schema. Global system tables can never be moved.
+
+
+
CLUSTER
+
Automatically maintain clustering on a table
+
This might require some background daemon to maintain clustering
+ during periods of low usage. It might also require tables to be only
+ paritally filled for easier reorganization. Another idea would
+ be to create a merged heap/index data file so an index lookup would
+ automatically access the heap data too. A third idea would be to
+ store heap rows in hashed groups, perhaps using a user-supplied
+ hash function.
+
+
Add default clustering to system tables
+
To do this, determine the ideal cluster index for each system
+ table and set the cluster setting during initdb.
+
+
+
COPY
+
Allow COPY to report error lines and continue
+
This requires the use of a savepoint before each COPY line is
+ processed, with ROLLBACK on COPY failure.
+
+
Allow COPY to understand \x as a hex byte
+
Have COPY return the number of rows loaded/unloaded (?)
+
Allow COPY to optionally include column headings in the first line
+
-Allow COPY FROM ... CSV to interpret newlines and carriage
+ returns in data
+
+
CURSOR
+
Allow UPDATE/DELETE WHERE CURRENT OF cursor
+
This requires using the row ctid to map cursor rows back to the
+ original heap row. This become more complicated if WITH HOLD cursors
+ are to be supported because WITH HOLD cursors have a copy of the row
+ and no FOR UPDATE lock.
+
+
Prevent DROP TABLE from dropping a row referenced by its own open
+ cursor (?)
+
Allow pooled connections to list all open WITH HOLD cursors
+
Because WITH HOLD cursors exist outside transactions, this allows
+ them to be listed so they can be closed.
+
+
+
INSERT
+
Allow INSERT/UPDATE of the system-generated oid value for a row
+
Allow INSERT INTO tab (col1, ..) VALUES (val1, ..), (val2, ..)
+
Allow INSERT/UPDATE ... RETURNING new.col or old.col
+
This is useful for returning the auto-generated key for an INSERT.
+ One complication is how to handle rules that run as part of
+ the insert.
+
+
+
SHOW/SET
+
Add SET PERFORMANCE_TIPS option to suggest INDEX, VACUUM, VACUUM
+ ANALYZE, and CLUSTER
+
Add SET PATH for schemas (?)
+
This is basically the same as SET search_path.
+
+
+
SERVER-SIDE LANGUAGES
+
Allow PL/PgSQL's RAISE function to take expressions (?)
+
Currently only constants are supported.
+
+
-Change PL/PgSQL to use palloc() instead of malloc()
+
Handle references to temporary tables that are created, destroyed,
+ then recreated during a session, and EXECUTE is not used
+
This requires the cached PL/PgSQL byte code to be invalidated when
+ an object referenced in the function is changed.
+
+
Fix PL/pgSQL RENAME to work on variables other than OLD/NEW
+
Allow function parameters to be passed by name,
+ get_employee_salary(emp_id => 12345, tax_year => 2001)
+
Add Oracle-style packages
+
Add table function support to pltcl, plperl, plpython (?)
+
Allow PL/pgSQL to name columns by ordinal position, e.g. rec.(3)
+
Allow PL/pgSQL EXECUTE query_var INTO record_var;
+
Add capability to create and call PROCEDURES
+
Allow PL/pgSQL to handle %TYPE arrays, e.g. tab.col%TYPE[]+
Add MOVE to PL/pgSQL
+
+
+
+
Add XML output to pg_dump and COPY
+
We already allow XML to be stored in the database, and XPath queries
+ can be used on that data using /contrib/xml2. It also supports XSLT
+ transformations.
+
+
Add a libpq function to support Parse/DescribeStatement capability
+
Prevent libpq's PQfnumber() from lowercasing the column name (?)
+
Allow libpq to access SQLSTATE so pg_ctl can test for connection failure
+
This would be used for checking if the server is up.
+
+
Have psql show current values for a sequence
+
Move psql backslash database information into the backend, use mnemonic
+
This would allow non-psql clients to pull the same information out of
+ the database as psql.
+
+
Fix psql's display of schema information (Neil)
+
Allow psql \pset boolean variables to set to fixed values, rather than toggle
+
Consistently display privilege information for all objects in psql
+
Improve psql's handling of multi-line queries
+
pg_dump
+
Have pg_dump use multi-statement transactions for INSERT dumps
+
Allow pg_dump to use multiple -t and -n switches
+
This should be done by allowing a '-t schema.table' syntax.
+
+
Add dumping of comments on composite type columns
+
Add dumping of comments on index columns
+
Replace crude DELETE FROM method of pg_dumpall for cleaning of
+ users and groups with separate DROP commands
+
Add dumping and restoring of LOB comments
+
Stop dumping CASCADE on DROP TYPE commands in clean mode
+
Add full object name to the tag field. eg. for operators we need
+ '=(integer, integer)', instead of just '='.
+
Add pg_dumpall custom format dumps.
+
This is probably best done by combining pg_dump and pg_dumpall
+ into a single binary.
+
+
Add CSV output format
+
Update pg_dump and psql to use the new COPY libpq API (Christopher)
+
+
ECPG
+
Docs
+
Document differences between ecpg and the SQL standard and
+ information about the Informix-compatibility module.
+
+
Solve cardinality > 1 for input descriptors / variables (?)
+
Add a semantic check level, e.g. check if a table really exists
+
fix handling of DB attributes that are arrays
+
Use backend PREPARE/EXECUTE facility for ecpg where possible
+
Implement SQLDA
+
Fix nested C comments
+
sqlwarn[6] should be 'W' if the PRECISION or SCALE value specified+
Make SET CONNECTION thread-aware, non-standard?
+
Allow multidimensional arrays
+
Add internationalized message strings
+
+
+
+
+
Add MATCH PARTIAL referential integrity
+
Add deferred trigger queue file
+
Right now all deferred trigger information is stored in backend
+ memory. This could exhaust memory for very large trigger queues.
+ This item involves dumping large queues into files.
+
+
Implement dirty reads or shared row locks and use them in RI triggers
+
Adding shared locks requires recording the table/rows numbers in a
+ shared area, and this could potentially be a large amount of data.
+ One idea is to store the table/row numbers in a separate table and set
+ a bit on the row indicating looking in this new table is required to
+ find any shared row locks.
+
+
Enforce referential integrity for system tables
+
Change foreign key constraint for array -> element to mean element
+ in array (?)
+
Allow DEFERRABLE UNIQUE constraints (?)
+
Allow triggers to be disabled [trigger]+
Currently the only way to disable triggers is to modify the system
+ tables.
+
+
With disabled triggers, allow pg_dump to use ALTER TABLE ADD FOREIGN KEY
+
If the dump is known to be valid, allow foreign keys to be added
+ without revalidating the data.
+
+
Allow statement-level triggers to access modified rows
+
Support triggers on columns (Greg Sabino Mullane)
+
Remove CREATE CONSTRAINT TRIGGER
+
This was used in older releases to dump referential integrity
+ constraints.
+
+
Allow AFTER triggers on system tables
+
System tables are modified in many places in the backend without going
+ through the executor and therefore not causing triggers to fire. To
+ complete this item, the functions that modify system tables will have
+ to fire triggers.
+
+
+
+
Flush cached query plans when the dependent objects change
+
Track dependencies in function bodies and recompile/invalidate
+
+
+
Add SQL99 WITH clause to SELECT
+
Add SQL99 WITH RECURSIVE to SELECT
+
Add pre-parsing phase that converts non-ISO syntax to supported
+ syntax
+
This could allow SQL written for other databases to run without
+ modification.
+
+
Allow plug-in modules to emulate features from other databases
+
SQL*Net listener that makes PostgreSQL appear as an Oracle database
+ to clients
+
Allow queries across databases or servers with transaction
+ semantics
+
Right now contrib/dblink can be used to issue such queries except it
+ does not have locking or transaction semantics. Two-phase commit is
+ needed to enable transaction semantics.
+
+
Add two-phase commit
+
This will involve adding a way to respond to commit failure by either
+ taking the server into offline/readonly mode or notifying the
+ administrator
+
+
+
+
+
Improve commit_delay handling to reduce fsync()
+
Determine optimal fdatasync/fsync, O_SYNC/O_DSYNC options
+
Allow multiple blocks to be written to WAL with one write()
+
Add an option to sync() before fsync()'ing checkpoint files
+
+
Allow free-behind capability for large sequential scans, perhaps using
+ posix_fadvise()
+
Posix_fadvise() can control both sequential/random file caching and
+ free-behind behavior, but it is unclear how the setting affects other
+ backends that also have the file open, and the feature is not supported
+ on all operating systems.
+
+
Consider use of open/fcntl(O_DIRECT) to minimize OS caching,
+ especially for WAL writes
+
-Cache last known per-tuple offsets to speed long tuple access
+
Speed up COUNT(*)
+
We could use a fixed row count and a +/- count to follow MVCC
+ visibility rules, or a single cached value could be used and
+ invalidated if anyone modifies the table. Another idea is to
+ get a count directly from a unique index, but for this to be
+ faster than a sequential scan it must avoid access to the heap
+ to obtain tuple visibility information.
+
+
Allow data to be pulled directly from indexes
+
Currently indexes do not have enough tuple tuple visibility
+ information to allow data to be pulled from the index without
+ also accessing the heap. One way to allow this is to set a bit
+ to index tuples to indicate if a tuple is currently visible to
+ all transactions when the first valid heap lookup happens. This
+ bit would have to be cleared when a heap tuple is expired.
+
+
Consider automatic caching of queries at various levels:
+
Parsed query tree
+
Query execute plan
+
Query results
+
+
-Allow the size of the buffer cache used by temporary objects to be
+ specified as a GUC variable
+
Larger local buffer cache sizes requires more efficient handling of
+ local cache lookups.
+
+
Improve the background writer
+
Allow the background writer to more efficiently write dirty buffers
+ from the end of the LRU cache and use a clock sweep algorithm to
+ write other dirty buffers to reduced checkpoint I/O
+
+
Allow sequential scans to take advantage of other concurrent
+ sequentiqal scans, also called "Synchronised Scanning"
+
+
+
Improve speed with indexes
+
For large table adjustements during vacuum, it is faster to reindex
+ rather than update the index.
+
+
Reduce lock time by moving tuples with read lock, then write
+ lock and truncate table
+
Moved tuples are invisible to other backends so they don't require a
+ write lock. However, the read lock promotion to write lock could lead
+ to deadlock situations.
+
+
-Add a warning when the free space map is too small
+
Maintain a map of recently-expired rows
+
This allows vacuum to reclaim free space without requiring
+ a sequential scan
+
+
Auto-vacuum
+
Move into the backend code
+
Scan the buffer cache to find free space or use background writer
+
Use free-space map information to guide refilling
+
Do VACUUM FULL if table is nearly empty?
+
+
+
+
Make locking of shared data structures more fine-grained
+
This requires that more locks be acquired but this would reduce lock
+ contention, improving concurrency.
+
+
Add code to detect an SMP machine and handle spinlocks accordingly
+ from distributted.net,
http://www1.distributed.net/source,+ in client/common/cpucheck.cpp
+
On SMP machines, it is possible that locks might be released shortly,
+ while on non-SMP machines, the backend should sleep so the process
+ holding the lock can complete and release it.
+
+
Improve SMP performance on i386 machines
+
i386-based SMP machines can generate excessive context switching
+ caused by lock failure in high concurrency situations. This may be
+ caused by CPU cache line invalidation inefficiencies.
+
+
Research use of sched_yield() for spinlock acquisition failure
+
Fix priority ordering of read and write light-weight locks (Neil)
+
+
+
Experiment with multi-threaded backend [thread]+
This would prevent the overhead associated with process creation. Most
+ operating systems have trivial process creation time compared to
+ database startup overhead, but a few operating systems (WIn32,
+ Solaris) might benefit from threading.
+
+
Add connection pooling
+
It is unclear if this should be done inside the backend code or done
+ by something external like pgpool. The passing of file descriptors to
+ existing backends is one of the difficulties with a backend approach.
+
+
+
+
Eliminate need to write full pages to WAL before page modification [wal]+
Currently, to protect against partial disk page writes, we write the
+ full page images to WAL before they are modified so we can correct any
+ partial page writes during recovery. These pages can also be
+ eliminated from point-in-time archive files.
+
+
Reduce WAL traffic so only modified values are written rather than
+ entire rows (?)
+
Turn off after-change writes if fsync is disabled
+
If fsync is off, there is no purpose in writing full pages to WAL
+
+
Add WAL index reliability improvement to non-btree indexes
+
Allow the pg_xlog directory location to be specified during initdb
+ with a symlink back to the /data location
+
Allow WAL information to recover corrupted pg_controldata
+
Find a way to reduce rotational delay when repeatedly writing
+ last WAL page
+
Currently fsync of WAL requires the disk platter to perform a full
+ rotation to fsync again. One idea is to write the WAL to different
+ offsets that might reduce the rotational delay.
+
+
Allow buffered WAL writes and fsync
+
Instead of guaranteeing recovery of all committed transactions, this
+ would provide improved performance by delaying WAL writes and fsync
+ so an abrupt operating system restart might lose a few seconds of
+ committed transactions but still be consistent. We could perhaps
+ remove the 'fsync' parameter (which results in an an inconsistent
+ database) in favor of this capability.
+
+
Eliminate WAL logging for CREATE TABLE AS when not doing WAL archiving
+
+
+
Add missing optimizer selectivities for date, r-tree, etc
+
Allow ORDER BY ... LIMIT 1 to select high/low value without sort or
+ index using a sequential scan for highest/lowest values
+
If only one value is needed, there is no need to sort the entire
+ table. Instead a sequential scan could get the matching value.
+
+
Precompile SQL functions to avoid overhead
+
Create utility to compute accurate random_page_cost value
+
Improve ability to display optimizer analysis using OPTIMIZER_DEBUG
+
Have EXPLAIN ANALYZE highlight poor optimizer estimates
+
Use CHECK constraints to influence optimizer decisions
+
CHECK constraints contain information about the distribution of values
+ within the table. This is also useful for implementing subtables where
+ a tables content is distributed across several subtables.
+
+
Consider using hash buckets to do DISTINCT, rather than sorting
+
This would be beneficial when there are few distinct values.
+
+
ANALYZE should record a pg_statistic entry for an all-NULL column
+
+
+
Do async I/O for faster random read-ahead of data
+
Async I/O allows multiple I/O requests to be sent to the disk with
+ results coming back asynchronously.
+
+
Use mmap() rather than SYSV shared memory or to write WAL files (?)
+
This would remove the requirement for SYSV SHM but would introduce
+ portability issues. Anonymous mmap (or mmap to /dev/zero) is required
+ to prevent I/O overhead.
+
+
Consider mmap()'ing files into a backend?
+
Doing I/O to large tables would consume a lot of address space or
+ require frequent mapping/unmapping. Extending the file also causes
+ mapping problems that might require mapping only individual pages,
+ leading to thousands of mappings. Another problem is that there is no
+ way to _prevent_ I/O to disk from the dirty shared buffers so changes
+ could hit disk before WAL is written.
+
+
Add a script to ask system configuration questions and tune postgresql.conf
+
Use a phantom command counter for nested subtransactions to reduce
+ per-tuple overhead
+
Consider parallel processing a single query
+
This would involve using multiple threads or processes to do optimization,
+ sorting, or execution of single query. The major advantage of such a
+ feature would be to allow multiple CPUs to work together to process a
+ single query.
+
+
Research the use of larger page sizes
+
+
+
Add use of 'const' for variables in source tree
+
Rename some /contrib modules from pg* to pg_*
+
Move some things from /contrib into main tree
+
Move some /contrib modules out to their own project sites
+
Remove warnings created by -Wcast-align
+
Move platform-specific ps status display info from ps_status.c to ports
+
Add optional CRC checksum to heap and index pages
+
Improve documentation to build only interfaces (Marc)
+
Remove or relicense modules that are not under the BSD license, if possible
+
Remove memory/file descriptor freeing before ereport(ERROR)
+
Acquire lock on a relation before building a relcache entry for it
+
Promote debug_query_string into a server-side function current_query()
+
Allow the identifier length to be increased via a configure option
+
Remove Win32 rename/unlink looping if unnecessary
+
Remove kerberos4 from source tree?
+
Allow cross-compiling by generating the zic database on the target system
+
Improve NLS maintenace of libpgport messages linked onto applications
+
Allow ecpg to work with MSVC and BCC
+
-Make src/port/snprintf.c thread-safe
+
Add xpath_array() to /contrib/xml2 to return results as an array
+
Allow building in directories containing spaces
+
This is probably not possible because 'gmake' and other compiler tools
+ do not fully support quoting of paths with spaces.
+
+
Allow installing to directories containing spaces
+
This is possible if proper quoting is added to the makefiles for the
+ install targets. Because PostgreSQL supports relocatable installs, it
+ is already possible to install into a directory that doesn't contain
+ spaces and then copy the install to a directory with spaces.
+
+
Fix cross-compiling of time zone database via 'zic'
+
Win32
+
Remove configure.in check for link failure when cause is found
+
Remove readdir() errno patch when runtime/mingwex/dirent.c rev
+ 1.4 is released
+
Remove psql newline patch when we find out why mingw outputs an
+ extra newline
+
Allow psql to use readline once non-US code pages work with
+ backslashes
+
Re-enable timezone output on log_line_prefix '%t' when a
+ shorter timezone string is available
+
Improve dlerror() reporting string
+
Fix problem with shared memory on the Win32 Terminal Server
+
Add support for Unicode
+
To fix this, the data needs to be converted to/from UTF16/UTF8
+ so the Win32 wcscoll() can be used, and perhaps other functions
+ like towupper(). However, UTF8 already works with normal
+ locales but provides no ordering or character set classes.
+
+
+
Wire Protocol Changes
+
Allow dynamic character set handling
+
Add decoded type, length, precision
+
Use compression?
+
Update clients to use data types, typmod, schema.table.column/ names+ of result sets using new query protocol
+
+
+
+
+
Developers who have claimed items are:
+ Family Health Network
+
+
+
+
projects / postgresql.git / commitdiff