> * Use UTF8 encoding for NLS messages so all server encodings can
> read them properly
< o %Add support for Unicode
<
< To fix this, the data needs to be converted to/from UTF16/UTF8
< so the Win32 wcscoll() can be used, and perhaps other functions
< like towupper(). However, UTF8 already works with normal
< locales but provides no ordering or character set classes.
< could only see committed rows from another transaction. However,
> could only see rows from another completed transaction. However,
981c981
< proper visibility of the row, for example, for cursors.
> proper visibility of the row's cmin, for example, for cursors.
* Merge xmin/xmax/cmin/cmax back into three header fields
Before subtransactions, there used to be only three fields needed to
store these four values. This was possible because only the current
transaction looks at the cmin/cmax values. If the current transaction
created and expired the row the fields stored where xmin (same as
xmax), cmin, cmax, and if the transaction was expiring a row from a
another transaction, the fields stored were xmin (cmin was not
needed), xmax, and cmax. Such a system worked because a transaction
could only see committed rows from another transaction. However,
subtransactions can see rows from outer transactions, and once the
subtransaction completes, the outer transaction continues, requiring
the storage of all four fields. With subtransactions, an outer
transaction can create a row, a subtransaction expire it, and when the
subtransaction completes, the outer transaction still has to have
proper visibility of the row, for example, for cursors.
One possible solution is to create a phantom cid which represents a
cmin/cmax pair and is stored in local memory.
< * Maintain a map of recently-expired rows
<
< This allows vacuum to target specific pages for possible free space
< without requiring a sequential scan.
<
Update entry:
> 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.
>
> 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.
> o Issue a warning if a change-on-restart-only postgresql.conf value
> is modified and the server config files are reloaded
> o Mark change-on-restart-only values in postgresql.conf
205a209
> o Fix SELECT '0.01 years'::interval, '0.01 months'::interval
>
> Currently, while \e saves a single query as one entry, interactive
> queries are saved one line at a time. Ideally all queries
> whould be saved like \e does.
>
> o Allow multi-line column values to align in the proper columns
>
> If the second output column value is 'a\nb', the 'b' should appear
> in the second display column, rather than the first column as it
> does now.
< in PL/PgSQL is to use EXECUTE.
> in PL/PgSQL is to use EXECUTE. One complexity is that a function
> might itself drop and recreate dependent tables, causing it to
> invalidate its own query plan.
< inheritance, and allow it to work for UPDATE and DELETE queries
> inheritance, allow it to work for UPDATE and DELETE queries, and allow
> it to be used for all queries with little performance impact
< * Allow constraint_elimination to be automatically performed
<
< This requires additional code to reduce the performance loss caused by
< constraint elimination.
< * -Allow limits on per-db/role connections
43d41
< * -Prevent dropping user that still owns objects, or auto-drop the objects
49d46
< * -Add the client IP address and port to pg_stat_activity
< * -Add session start time and last statement time to pg_stat_activity
< * -Add a function that returns the start time of the postmaster
230d224
< o -Allow MIN()/MAX() on arrays
< o -Modify array literal representation to handle array index lower bound
< of other than one
253d244
< * -Add function to return compressed length of TOAST data values
< * -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.
<
< * -Have views on temporary tables exist in the temporary namespace
< * -Allow temporary views on non-temporary tables
329d311
< * -Add BETWEEN SYMMETRIC/ASYMMETRIC
< * -Add E'' escape string marker so eventually ordinary strings can treat
< backslashes literally, for portability
<
< * -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.
<
341d313
< * -Allow REINDEX to rebuild all database indexes
< * -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.
<
426d391
< o -Allow FOR UPDATE queries to do NOWAIT locks
473d437
< o -Allow COPY to understand \x as a hex byte
< 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
525d485
< o -Have SHOW ALL show descriptions for server-side variables
< o -Allow PL/PgSQL's RAISE function to take expressions
<
< Currently only constants are supported.
<
< o -Change PL/PgSQL to use palloc() instead of malloc()
545d499
< o -Allow PL/pgSQL EXECUTE query_var INTO record_var;
550d503
< o -Pass arrays natively instead of as text between plperl and postgres
598d550
< o -Add dumping and restoring of LOB comments
638d589
< * -Implement shared row locks and use them in RI triggers
642d592
< * -Allow triggers to be disabled
< * -Add two-phase commit
<
<
< * -Prevent inherited tables from expanding temporary subtables of other
< sessions
< * -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.
<
< * -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.
<
< * -Fix incorrect rtree results due to wrong assumptions about "over"
< operator semantics
782d694
< o -Add concurrency to GIST
813d724
< * -Allow multiple blocks to be written to WAL with one write()
< * -Consider use of open/fcntl(O_DIRECT) to minimize OS caching,
< for WAL writes
<
< O_DIRECT doesn't have the same media write guarantees as fsync, so it
< is in addition to the fsync method, not in place of it.
<
< * -Cache last known per-tuple offsets to speed long tuple access
< * -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
<
897d788
< * -Add a warning when the free space map is too small
917d807
< o -Move into the backend code
< * -Make locking of shared data structures more fine-grained
<
< This requires that more locks be acquired but this would reduce lock
< contention, improving concurrency.
<
< * -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.
<
979d857
< o -Add ability to turn off full page writes
< * -Eliminate WAL logging for CREATE TABLE AS when not doing WAL archiving
< * -Change WAL to use 32-bit CRC, for performance reasons
<
< * -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.
<
1045d913
< * -ANALYZE should record a pg_statistic entry for an all-NULL column
1099d966
< * -Remove kerberos4 from source tree
1103d969
< * -Make src/port/snprintf.c thread-safe
1118d983
< * -Add C code on Unix to copy directories for use in creating new databases
1133d997
< o -Improve dlerror() reporting string
< Currently SIGTERM of a backend can lead to lock table corruption.
> Lock table corruption following SIGTERM of an individual backend
> has been reported in 8.0. A possible cause was fixed in 8.1, but
> it is unknown whether other problems exist. This item mostly
> requires additional testing rather than of writing any new code.
< o Allow postgresql.conf values to be set so they can not be changed
< by the user
166c167,171
< * %Remove Money type, add money formatting for decimal type
> * Improve the MONEY data type
>
> Change the MONEY data type to use DECIMAL internally, with special
> locale-aware output formatting.
>
225c230
< o %Allow MIN()/MAX() on arrays
> o -Allow MIN()/MAX() on arrays
228c233
< o Modify array literal representation to handle array index lower bound
> o -Modify array literal representation to handle array index lower bound
235a241
> o Auto-delete large objects when referencing row is deleted
< Currently large objects entries do not have owners. Permissions can
< only be set at the pg_largeobject table level.
> /contrib/lo offers this functionality.
240d244
< o Auto-delete large objects when referencing row is deleted
< * %Have views on temporary tables exist in the temporary namespace
< * Allow temporary views on non-temporary tables
< * %Allow RULE recompilation
> * -Have views on temporary tables exist in the temporary namespace
> * -Allow temporary views on non-temporary tables
> * Allow VIEW/RULE recompilation when the underlying tables change
340a345,347
>
> This is like DELETE CASCADE, but truncates.
>
381c388
< * Make row-wise comparisons work per SQL spec
> * %Make row-wise comparisons work per SQL spec
< o Currently the system uses the operating system COPY command to
< create a new database. Add ON COMMIT capability to CREATE TABLE AS
< SELECT
> o Add ON COMMIT capability to CREATE TABLE AS ... SELECT
427c432
< o %Add ALTER DOMAIN TYPE
> o Add ALTER DOMAIN to modify the underlying data type
< o %Disallow dropping of an inherited constraint
< o -Allow objects to be moved to different schemas
> o Add missing object types for ALTER ... SET SCHEMA
< o %Prevent child tables from altering constraints like CHECK that were
< inherited from the parent table
> o %Disallow dropping of an inherited constraint
> o %Prevent child tables from altering or dropping constraints
> like CHECK that were inherited from the parent table
< o Handle references to temporary tables that are created, destroyed,
< then recreated during a session, and EXECUTE is not used
<
< This requires the cached PL/PgSQL byte code to be invalidated when
< an object referenced in the function is changed.
<
< o Add table function support to pltcl, plperl, plpython?
< o Allow PL/pgSQL to name columns by ordinal position, e.g. rec.(3)
> o Add table function support to pltcl, plpython
549a548
> o Allow function argument names to be queries from PL/PgSQL
< o Pass arrays natively instead of as text between plperl and postgres
< o Add support for polymorphic arguments and return types to plperl
> o -Pass arrays natively instead of as text between plperl and postgres
> o Add support for polymorphic arguments and return types to
> languages other than PL/PgSQL
> o Add support for OUT and INOUT parameters to languages other
> than PL/PgSQL
< * Allow libpq to access SQLSTATE so pg_ctl can test for connection failure
<
< This would be used for checking if the server is up.
<
565c563
< * Have initdb set DateStyle based on locale?
> * Have initdb set the input DateStyle (MDY or DMY) based on locale?
567d564
< * Add a schema option to createlang
< o Add pg_dumpall custom format dumps.
<
< This is probably best done by combining pg_dump and pg_dumpall
< into a single binary.
<
> o Add pg_dumpall custom format dumps?
612c605,606
< o Remove unnecessary abstractions in pg_dump source code
> o Remove unnecessary function pointer abstractions in pg_dump source
> code
< * %Remove CREATE CONSTRAINT TRIGGER
<
< This was used in older releases to dump referential integrity
< constraints.
<
682a672,675
> This is particularly important for references to temporary tables
> in PL/PgSQL because PL/PgSQL caches query plans. The only workaround
> in PL/PgSQL is to use EXECUTE.
>
748c741
< * Fetch heap pages matching index entries in sequential order
> * -Fetch heap pages matching index entries in sequential order
797c790
< Currently no only one hash bucket can be stored on a page. Ideally
> Currently only one hash bucket can be stored on a page. Ideally
806a800,802
> o Add WAL logging for crash recovery
> o Allow multi-column hash indexes
>
812a809,812
>
> Ideally this requires a separate test program that can be run
> at initdb time or optionally later.
>
867c867
< * Improve the background writer
> * -Improve the background writer
< For large table adjustements during vacuum, it is faster to reindex
< rather than update the index.
> For large table adjustements during VACUUM FULL, 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
> * Reduce lock time during VACUUM FULL by moving tuples with read lock,
> then write lock and truncate table
919c919,920
< o %Suggest VACUUM FULL if a table is nearly empty
> o %Issue log message to suggest VACUUM FULL if a table is nearly
> empty?
995d995
< * Add WAL index reliability improvement to non-btree indexes
1045c1045
< * ANALYZE should record a pg_statistic entry for an all-NULL column
> * -ANALYZE should record a pg_statistic entry for an all-NULL column
1047a1048,1051
> * Allow constraint_elimination to be automatically performed
>
> This requires additional code to reduce the performance loss caused by
> constraint elimination.
1090c1094
< * Remove memory/file descriptor freeing before ereport(ERROR)
> * %Remove memory/file descriptor freeing before ereport(ERROR)
< * Promote debug_query_string into a server-side function current_query()
< * Allow the identifier length to be increased via a configure option
> * %Promote debug_query_string into a server-side function current_query()
> * %Allow the identifier length to be increased via a configure option
1113d1116
< * Fix cross-compiling of time zone database via 'zic'
1130c1133
< o Improve dlerror() reporting string
> o -Improve dlerror() reporting string
1132c1135
< o Add support for Unicode
> o %Add support for Unicode
< Currently, if a variable is commented out, it keeps the
< previous uncommented value until a server restarted.
> Currently, if a variable is commented out, it keeps the
> previous uncommented value until a server restarted.
> Logically, a reload should set the same values as a
> server restart.
< * Allow triggers to be disabled [trigger]
> * -Allow triggers to be disabled [trigger]
> * Allow triggers to be disabled in only the current session.
< Currently the only way to disable triggers is to modify the system
< tables.
> 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 idea for this usage.
< inheritance
< * Allow enable_constraint_exclusion to work for UPDATE and DELETE queries
> inheritance, and allow it to work for UPDATE and DELETE queries
< o Allow objects to be moved to different schemas
> o -Allow objects to be moved to different schemas
Fix word wrap:
< * Allow GRANT/REVOKE permissions to be applied to all schema objects with one
< command
> o Allow GRANT/REVOKE permissions to be applied to all schema objects
> with one command
< 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.
> This would add a function to load the SQL table from
> pg_hba.conf, and one to writes its contents to the flat file.
> The table should have a line number that is a float so rows
> can be inserted between existing rows, e.g. row 2.5 goes
> between row 2 and row 3.
< o Allow postgresql.conf file values to be changed via an SQL API
> o Allow postgresql.conf file values to be changed via an SQL
> API, perhaps using SET GLOBAL
<
> * Allow EXPLAIN to identify tables that were skipped because of
> enable_constraint_exclusion
> * Allow EXPLAIN output to be more easily processed by scripts
760a763
> * Allow enable_constraint_exclusion to work for UPDATE and DELETE queries
> * Add TRUNCATE permission
>
> Currently only the owner can TRUNCATE a table because triggers are not
> called, and the table is locked in exclusive mode.
>
< * Consider use of open/fcntl(O_DIRECT) to minimize OS caching,
< especially for WAL writes
> * -Consider use of open/fcntl(O_DIRECT) to minimize OS caching,
> for WAL writes
< 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.
<
> computations should adjust based on the time zone rules.
< writer.
> 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.
>
> o -Add ability to turn off full page writes
> o When off, write CRC to WAL and check file system blocks
> on recovery
> 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.
< Currently, to protect against partial disk page writes, we write the
> Currently, to protect against partial disk page writes, we write
877c877
< * Turn off after-change writes if fsync is disabled
> * Turn off full page writes if fsync is disabled
< o Replace crude DELETE FROM method of pg_dumpall for cleaning of
< roles with separate DROP commands
> o Replace crude DELETE FROM method of pg_dumpall --clean for
> cleaning of roles with separate DROP commands
< * Allow limits on per-db/user connections
> * Allow limits on per-db/role connections
< * Prevent default re-use of sysids for dropped users and roles
<
< 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.
<
450c444
< * Add COMMENT ON for all cluster global objects (users, roles, databases
> * Add COMMENT ON for all cluster global objects (roles, databases
609c603
< users and roles with separate DROP commands
> roles with separate DROP commands
< * Prevent default re-use of sysids for dropped users and groups
> * Prevent default re-use of sysids for dropped users and roles
450c450
< * Add COMMENT ON for all cluster global objects (users, groups, databases
> * Add COMMENT ON for all cluster global objects (users, roles, databases
609c609
< users and groups with separate DROP commands
> users and roles with separate DROP commands
> * Add NUMERIC division operator that doesn't round?
>
> Currently NUMERIC _rounds_ the result to the specified precision.
> This means division can return a result that multiplied by the
> divisor is greater than the dividend, e.g. this returns a value > 10:
>
> SELECT (10::numeric(2,0) / 6::numeric(2,0))::numeric(2,0) * 6;
>
> The positive modulus result returned by NUMERICs might be considered
> inaccurate, in one sense.
>
< * 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
< because backends must first do a query cancel, then exit once they
< have run the query cancel cleanup routine.
<
> * Allow administrators to safely terminate individual sessions either
> via an SQL function or SIGTERM
> * Auto-fill the free space map by scanning the buffer cache or by
> checking pages written by the background writer
< * Auto-fill the free space map by scanning the buffer cache or by
< checking pages written by the background writer
>
> * 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.
< o Allow databases and schemas to be moved to different tablespaces
<
< One complexity is whether moving a schema should move all existing
< schema objects or just define the location for future object creation.
<
> o Allow databases to be moved to different tablespaces
484c480
< schema. Global system tables can never be moved.
> tablespace. Global system tables can never be moved.
< changes made by the interface driver for its internal use. One idea is
< for this to be a protocol-only feature. Another approach is to notify
< the protocol when a RESET CONNECTION command is used.
> changes made by the interface driver for its internal use. One idea
> is for this to be a protocol-only feature. Another approach is to
> notify the protocol when a RESET CONNECTION command is used.
< 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.
> temporary tables, removing any NOTIFYs, cursors, open transactions,
> prepared queries, currval()s, etc. This could be used for connection
> pooling. We could also change RESET ALL to have this functionality.
> The difficult of this features is allowing RESET ALL to not affect
> changes made by the interface driver for its internal use. One idea is
> for this to be a protocol-only feature. Another approach is to notify
> the protocol when a RESET CONNECTION command is used.
< cleaned up properly. A new signal is needed for safe termination.
> cleaned up properly. A new signal is needed for safe termination
> because backends must first do a query cancel, then exit once they
> have run the query cancel cleanup routine.
< logs
> logs [pitr]
130c130
< * Allow a warm standby system to also allow read-only queries
> * Allow a warm standby system to also allow read-only queries [pitr]
> * 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.
>
< * Prevent child tables from altering constraints like CHECK that were
< inherited from the parent table
470a469,471
>
> o Prevent child tables from altering constraints like CHECK that were
> inherited from the parent table
<
< * 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.
> * 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
> * Add the features of packages
> o Make private objects accessable only to objects in the same schema
> o Allow current_schema.objname to access current schema objects
> o Add session variables
> o Allow nested schemas
<
< This will involve adding a way to respond to commit failure by either
< taking the server into offline/readonly mode or notifying the
< administrator
< * Add session start time and last statement time to pg_stat_activity
> * -Add session start time and last statement time to pg_stat_activity
134c134
< * Add the client IP address and port to pg_stat_activity
> * -Add the client IP address and port to pg_stat_activity
< Currently locale can only be set during initdb.
> 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.
> * Prevent to_char() on interval from returning meaningless values
>
> For example, to_char('1 month', 'mon') is meaningless. Basically,
> most date-related parameters to to_char() are meaningless for
> intervals because interval is not anchored to a date.
>
> * Allow to_char() on interval values to accumulate the highest unit
> requested
>
> o to_char(INTERVAL '1 hour 5 minutes', 'MI') => 65
> o to_char(INTERVAL '43 hours 20 minutes', 'MI' ) => 2600
> o to_char(INTERVAL '43 hours 20 minutes', 'WK:DD:HR:MI') => 0:1:19:20
> o to_char(INTERVAL '3 years 5 months','MM') => 41
>
> Some special format flag would be required to request such
> accumulation. Such functionality could also be added to EXTRACT.
> Prevent accumulation that crosses the month/day boundary because of
> the uneven number of days in a month.
>
< * Allow ORDER BY ... LIMIT 1 to select high/low value without sort or
> * Allow ORDER BY ... LIMIT # to select high/low value without sort or
868c868
< Right now, if no index exists, ORDER BY ... LIMIT 1 requires we sort
> Right now, if no index exists, ORDER BY ... LIMIT # requires we sort
870a871
> MIN/MAX already does this, but not for LIMIT > 1.
> * Allow ORDER BY ... LIMIT 1 to select high/low value without sort or
> index using a sequential scan for highest/lowest values
>
> Right now, if no index exists, ORDER BY ... LIMIT 1 requires we sort
> all values to return the high/low value. Instead The idea is to do a
> sequential scan to find the high/low value, thus avoiding the sort.
>
> One possible implementation is to start sequential scans from the lowest
> numbered buffer in the shared cache, and when reaching the end wrap
> around to the beginning, rather than always starting sequential scans
> at the start of the table.
< This allows vacuum to reclaim free space without requiring
< a sequential scan
> This allows vacuum to target specific pages for possible free space
> without requiring a sequential scan.
< * 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.
<
< * 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.
<
< Solaris) might benefit from threading.
> Solaris) might benefit from threading. Also explore the idea of
> a single session using multiple threads to execute a query faster.
< 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.
> Currently indexes do not have enough tuple visibility information
> to allow data to be pulled from the index without also accessing
> the heap. One way to allow this is to set a bit to index tuples
> to indicate if a tuple is currently visible to all transactions
> when the first valid heap lookup happens. This bit would have to
> be cleared when a heap tuple is expired.
< 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).
> 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.
Bruce Momjian