<!--
-$PostgreSQL: pgsql/doc/src/sgml/release.sgml,v 1.361 2005/08/24 19:41:33 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/release.sgml,v 1.362 2005/08/24 22:03:14 tgl Exp $
Typical markup:
<title>Release date</title>
<simpara>2005-1?-??, Current as of 2005-08-24</simpara>
</note>
-
+
<sect2>
<title>Overview</title>
<varlistentry>
<term>
- Automatically use indexes for <function>MIN()</> and
- <function>MAX()</> (Tom)
- </term>
-
- <listitem>
- <para>
- In previous releases, the only way to use an index for
- <function>MIN()</> or <function>MAX()</> was to rewrite the
- query as <command>SELECT col FROM tab ORDER BY col LIMIT 1</>.
- Index usage now happens automatically.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>
- Add in-memory bitmaps which allows multiple indexes to be merged
- in a single query (Tom)
+ Allow index scans to use an intermediate in-memory bitmap (Tom)
</term>
<listitem>
lookups on a table. With this feature, if a query has
<command>WHERE tab.col1 = 4 and tab.col2 = 9</>, and there is no
multicolumn index on col1 and col2, but there is an index on
- col1 and another on col2, it is possible to do lookups on the
- col1 index and the col2 index and combine them in memory to do
- heap lookups on rows matching both the col1 and col2
+ col1 and another on col2, it is possible to search both indexes
+ and combine the results in memory, then do heap fetches for only
+ the rows matching both the col1 and col2
restrictions. This is very useful in environments that have a
lot of unstructured queries where it is impossible to create
- indexes that match all possible access conditions.
+ indexes that match all possible access conditions. Bitmap scans
+ are useful even with a single index, as they reduce the amount
+ of random access needed; a bitmap index scan is efficient for
+ retrieving fairly large fractions of the complete table, whereas
+ plain index scans are not.
</para>
</listitem>
</varlistentry>
computers, and once all computers have successfully prepared
their transactions (none failed), all transactions can be
committed. Even if a machine crashes after a prepare, the
- prepared transaction can be committed after it is restarted. New
- syntax includes <command>PREPARE TRANSACTION</> and
+ prepared transaction can be committed after the machine is
+ restarted. New syntax includes <command>PREPARE TRANSACTION</> and
<command>COMMIT/ROLLBACK PREPARED</>. A new system view
<literal>pg_prepared_xacts</> has also been added.
</para>
<listitem>
<para>
- Have optionally have login capability
+ Have login capability (optionally)
</para>
</listitem>
<listitem>
<para>
- Inherit permission from other member roles
+ Hold access permissions for database objects
</para>
</listitem>
<listitem>
<para>
- Switch to another member role using <command>SET ROLE</>
+ Inherit permissions from other roles it is a member of
</para>
</listitem>
</itemizedlist>
<para>
- So, once a user logs into a role, she inherits capabilities of
+ Once a user logs into a role, she obtains capabilities of
the login role plus any inherited roles, and can use
- <command>SET ROLE</> to switch to other member roles. This
- change also replaces <literal>pg_shadow</> and
- <literal>pg_group</> by with new role-capable catalogs
- <literal>pg_authid</> and <literal>pg_auth_members</>. The old
- tables are redefined as views on the new role tables.
+ <command>SET ROLE</> to switch to other roles she is a member of.
+ This feature is a generalization of the SQL standard's concept of
+ roles.
+ This change also replaces <structname>pg_shadow</> and
+ <structname>pg_group</> by new role-capable catalogs
+ <structname>pg_authid</> and <structname>pg_auth_members</>. The old
+ tables are redefined as read-only views on the new role tables.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
- Move <filename>/contrib/pgautovacuum</> into the main server
+ Automatically use indexes for <function>MIN()</> and
+ <function>MAX()</> (Tom)
+ </term>
+
+ <listitem>
+ <para>
+ In previous releases, the only way to use an index for
+ <function>MIN()</> or <function>MAX()</> was to rewrite the
+ query as <command>SELECT col FROM tab ORDER BY col LIMIT 1</>.
+ Index usage now happens automatically.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>
+ Move <filename>/contrib/pg_autovacuum</> into the main server
(Alvaro Herrera)
</term>
<listitem>
<para>
- Moving pgautovacuum from <filename>/contrib</> allows it to be
+ Integrating autovacuum into the server allows it to be
automatically started and stopped in sync with the database
- server, and allows for pgautovacuum to be configured from
+ server, and allows autovacuum to be configured from
<filename>postgresql.conf</>.
</para>
</listitem>
allows <command>SELECT</> to never be blocked by writers and
therefore does not need shared row locks for typical operations,
shared locks are useful for applications that require shared row
- locking, and to reduce the locking requirements to maintain
- referential integrity.
+ locking. In particular this reduces the locking requirements
+ imposed by referential integrity checks.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>
+ Add dependencies on shared objects, specifically roles
+ (Alvaro)
+ </term>
+
+ <listitem>
+ <para>
+ This extension of the dependency mechanism prevents roles from
+ being dropped while there are still database objects they own.
+ Formerly it was possible to accidentally <quote>orphan</> objects by
+ deleting their owner. While this could be recovered from, it
+ was messy and unpleasant.
</para>
</listitem>
</varlistentry>
<para>
The 8.0 release announced that the <function>to_char()</> function
for intervals would be removed in 8.1. However, since no better API
- has been suggested, to_char(interval) has been enhanced in 8.1 and
- will remain in the server.
+ has been suggested, <function>to_char(interval)</> has been enhanced in
+ 8.1 and will remain in the server.
</para>
<para>
<listitem>
<para>
- Change add_missing_from to 'false'
+ <varname>add_missing_from</> is now false by default (Neil)
</para>
<para>
- Generate an error if a table used in a query without a
- <command>FROM</> reference (Neil) This command, <command>SELECT
- pg_class.*</>, now generates an error.
+ By default, we now generate an error if a table is used in a query
+ without a <command>FROM</> reference. The old behavior is still
+ available, but the parameter must be set to 'true' to obtain it.
</para>
</listitem>
<listitem>
<para>
- Cause input of a zero-length strings ('') for float4/float8/oid
- to throw an error, rather than treat it as a zero (Neil)
+ Cause input of a zero-length string ('') for float4/float8/oid
+ to throw an error, rather than treating it as a zero (Neil)
</para>
<para>
This change is consistent with the current handling of
<listitem>
<para>
- Change <varname>default_with_oids</> to default to false (Neil)
+ <varname>default_with_oids</> is now false by default (Neil)
</para>
<para>
With this option set to false, user-created tables no longer have
- an the usually-invisible OID column unless <command>WITH OIDS</>
+ the usually-invisible OID column unless <command>WITH OIDS</>
is specified in <command>CREATE TABLE</>. Though OIDs have
- existed in all previous releases of
+ existed in all releases of
<productname>PostgreSQL</productname>, their use is limited
- because they are only four bytes long and the counter is unique
+ because they are only four bytes long and the counter is shared
across all installed databases. The preferred way of uniquely
identifying rows is via sequences and <command>SERIAL</>, which
- ha
s been supported since <productname>PostgreSQL</productname>
+ ha
ve been supported since <productname>PostgreSQL</productname>
6.4.
</para>
</listitem>
</para>
<para>
Currently <productname>PostgreSQL</productname> processes a
- backslash in a string as preceeding a character that requires
- special processing, e.g. <literal>\n</> or <literal>\010</>.
+ backslash in a string literal as introducing a special escape sequence,
+ e.g. <literal>\n</> or <literal>\010</>.
While this allows easy entry of special values, it is
- non-standard and makes porting of application from other
+ non-standard and makes porting of applications from other
databases more difficult. For this reason, the
<productname>PostgreSQL</productname> project is planning to
remove the special meaning of backslashes in strings. For
backward compatibility and for users who want special backslash
- processing, a new string type will be created. This new string
- type is formed by having an E precede the single quote that
- starts the string, e.g. <literal>E'hi\n'</>. While this release
- does not change the handling of backslashes in strings, it does
- add several new GUC variables to help users migrate applications
+ processing, a new string syntax has been created. This new string
+ syntax is formed by writing an <literal>E</> immediately preceding the
+ single quote that starts the string, e.g. <literal>E'hi\n'</>. While
+ this release does not change the handling of backslashes in strings, it
+ does add new GUC variables to help users migrate applications
for future releases:
</para>
<itemizedlist>
-
- <listitem>
- <para>
- <varname>escape_string_warning</> - warn about backslashes in
- ordinary (non-E) strings
- </para>
- </listitem>
-
- <listitem>
- <para>
- <varname>escape_string_syntax</> - does this release support
- the E'' syntax?
- </para>
- </listitem>
<listitem>
<para>
treat backslashes literally in ordinary strings?
</para>
</listitem>
+
+ <listitem>
+ <para>
+ <varname>escape_string_warning</> - warn about backslashes in
+ ordinary (non-E) strings
+ </para>
+ </listitem>
</itemizedlist>
<para>
- The last two values are read-only and should assist in the
- porting of applications. Applications can retrieve these values
- to know how backslashes are processed. In a later release,
- standard_conforming_strings will be true, meaning backslashes
- will be treated literally in non-E strings. To prepare for this
- change, use E'' strings in places that need special backslash
- processing, and turn on escape_string_warning to find additional
- strings that need to be converted to use <literal>E''</>. Also,
- use two single-quotes ('') to embed a literal single-quote
- in a string, rather than the PostgreSQL-supported syntax of
- backslash single-quote (\'). The former is standards-conforming
- and does not require the use of the E'' string syntax. You can
- also use the $$ string syntax, which does not treat backslashes
+ The <varname>standard_conforming_strings</> value is read-only.
+ Applications can retrieve the value to know how backslashes are
+ processed. (Presence of the parameter can also be taken as an
+ indication that <literal>E''</> string syntax is supported.) In a
+ future release, <varname>standard_conforming_strings</> will be true,
+ meaning backslashes will be treated literally in non-E strings. To
+ prepare for this change, use <literal>E''</> strings in places that
+ need special backslash processing, and turn on
+ <varname>escape_string_warning</> to find additional strings that need
+ to be converted to use <literal>E''</>. Also, use two single-quotes
+ (<literal>''</>) to embed a literal single-quote in a string, rather
+ than the PostgreSQL-supported syntax of backslash single-quote
+ (<literal>\'</>). The former is standards-conforming and does not
+ require the use of the <literal>E''</> string syntax. You can also use
+ the <literal>$$</> string syntax, which does not treat backslashes
specially.
</para>
</listitem>
<listitem>
<para>
- Change WAL CRC records from 64bit to 32bit (Tom)
+ Change WAL record CRCs from 64-bit to 32-bit (Tom)
+ </para>
+ <para>
+ We determined that the extra cost of computing 64-bit CRCs was
+ significant, and the gain in reliability too marginal to justify it.
</para>
</listitem>
<para>
Since a crash during <command>CREATE TABLE</> would cause the
table to be dropped during recovery, there is no reason to WAL
- log as the table is loaded.
+ log as the table is loaded. (Logging still happens if WAL
+ archiving is enabled, however.)
</para>
</listitem>
To prevent partial disk writes from corrupting the database,
<productname>PostgreSQL</productname> writes a complete copy of
each database disk page to WAL the first time it is modified
- after a checkpoint. This turns off that functionality for users
- with battery-backed disk caches where partial page writes cannot
- happen.
+ after a checkpoint. This option turns off that functionality for more
+ speed. This is safe to use with battery-backed disk caches where
+ partial page writes cannot happen.
</para>
</listitem>
on table constraints (Simon)
</para>
<para>
- This allows for a type of table partitioning. If child table
- placed in a different tablespaces using appropriate
+ This allows for a type of table partitioning. If child tables
+ store separate key ranges and this is enforced using appropriate
<command>CHECK</> constraints, the optimizer will skip child
- table accesses if the constraint guarantees no matching rows
+ table accesses when the constraint guarantees no matching rows
exist in the child table.
</para>
</listitem>
Prevent problems due to transaction ID (XID) wraparound (Tom)
</para>
<para>
- This was accomplished by warning the transaction counter is near
- the the earliest transaction id determined by the database whose
- last vacuum is the oldest. If the limit is reached, the server
- will no longer accept queries.
+ The server will now warn when the transaction counter approaches
+ the wraparound point. If the counter becomes too close to wraparound,
+ the server will stop accepting queries. This ensures that data is
+ not lost before needed vacuuming is performed.
</para>
</listitem>
<listitem>
<para>
- Fix problem of object ID (OID) wraparound conflicting with
- existing system objects (Tom)
+ Fix problems with object IDs (OIDs) conflicting with existing system
+ objects after the OID counter has wrapped around (Tom)
</para>
</listitem>
Add GUC variables to control TCP/IP keep-alive times for idle,
interval, and count (Oliver Jowett)
</para>
+
+ <para>
+ These values can be changed to allow more rapid detection of
+ lost client connections.
+ </para>
</listitem>
<listitem>
</para>
<para>
Using <command>ALTER USER</> and <command>ALTER DATABASE</>,
- limits can now be enforced on the maximum number of users who
- can connect as as a specific user or to a specific database.
+ limits can now be enforced on the maximum number of sessions that
+ can concurrently connect as a specific user or to a specific database.
Setting the limit to zero disables user or database connections.
</para>
</listitem>
UPDATE/SHARE</> (Hans-Juergen Schoenig)
</para>
<para>
- While <command>SET</> statement_timeout allows a query taking
- over a certain amount of time to be cancelled, the <command>NO
- WAIT</> option allows a query to be canceled as soon as a
- <command>SELECT ... FOR UPDATE/SHARE</> cannot immediately
+ While <command>SET</> <varname>statement_timeout</> allows a query
+ taking over a certain amount of time to be cancelled, the
+ <command>NOWAIT</> option allows a query to be canceled as soon as a
+ <command>SELECT ... FOR UPDATE/SHARE</> command cannot immediately
acquire a row lock.
</para>
</listitem>
by the object owner (Stephen Frost)
</para>
<para>
- Prior releases allowed only the super-user to change object owners,
- even if the current owner was executing the command and the new
- owner was in the same group. With roles such transfers are now
- possible.
+ Prior releases allowed only superusers to change object owners.
+ Now, ownership can be transferred if the user executing the command
+ owns the object and would be able to create it as the new owner
+ (that is, the user is a member of the new owning role and that role
+ has the CREATE permission that would be needed to create the object
+ afresh).
</para>
</listitem>
single command (Alvaro)
</para>
<para>
- Because of referential integrity checks, it is impossible to
+ Because of referential integrity checks, it is not allowed to
truncate a table that is part of a referential integrity
constraint. Using this new functionality, <command>TRUNCATE</>
- can be used to truncate all tables involved in referential
- integrity if they are truncated in a single <command>TRUNCATE</>
- command.
+ can be used to truncate such tables, if both tables involved in
+ a referential integrity constraint are truncated in a single
+ <command>TRUNCATE</> command.
</para>
</listitem>
<listitem>
<para>
- On Win32, display better sub-second precision in
+ On Windows, display better sub-second precision in
<command>EXPLAIN ANALYZE</> (Magnus)
</para>
</listitem>
(Tom)
</para>
<para>
- Prior releases accumulated trigger execution time as part of the
- total execution time.
+ Prior releases included trigger execution time as part of the
+ total execution time, but did not show it separately. It is now
+ possible to see how much time is spent in each trigger.
</para>
</listitem>
<listitem>
<para>
- Have <command>SHOW ALL</> include variable descriptions
+ Make <command>SHOW ALL</> include variable descriptions
(Matthias Schmidt)
</para>
<para>
<listitem>
<para>
- Have initdb create new standard database called
- <literal>postgres</> and convert utilities to use
+ Make initdb create a new standard database called
+ <literal>postgres</>, and convert utilities to use
<literal>postgres</> rather than <literal>template1</> for
standard lookups (Dave)
</para>
<para>
- In prior releases, template1 was used both as a default
+ In prior releases, <literal>template1</> was used both as a default
connection for utilities like createuser, and as a template for
new databases. This caused <command>CREATE DATABASE</> to
- sometimes fail because a new database cannot be created if
+ sometimes fail, because a new database cannot be created if
anyone else is in the template database. With this change, the
default connection database is now <literal>postgres</>, meaning
it is much less likely someone will be using
Add <function>MAX()</> and <function>MIN()</> aggregates for
array types (Koju Iijima)
</para>
- <para>
- How does this work?
- </para>
</listitem>
<listitem>
If the format specification contains <literal>CC</> and a year
specification is <literal>YYY</> or longer, ignore the
<literal>CC</>. If the year specification is <literal>YY</> or
- shorter, interpret <literal>CC</> as the previous century. ?
+ shorter, interpret <literal>CC</> as the previous century.
</para>
</listitem>
<listitem>
<para>
- Add support for <command>NUMERIC ^ NUMERIC</> based on
+ Add support for <command>numeric ^ numeric</> based on
<function>power(numeric, numeric)</>
</para>
<para>
</para>
<para>
In previous releases, modulus for large values sometimes
- returned negative results due to the rounding of the quotient.
+ returned negative results due to rounding of the quotient.
</para>
</listitem>
</para>
<para>
These functions take a variable number of arguments and return
- the greatest or least value.
+ the greatest or least value among the arguments.
</para>
</listitem>
Add <function>regexp_replace()</> (Atsushi Ogawa)
</para>
<para>
- This allows regular expression replacement, like sed. A
- four-argument version also allows for global (replace all) and
+ This allows regular expression replacement, like sed. An optional
+ flag argument allows selection of global (replace all) and
case-insensitive modes.
</para>
</listitem>
(not fixed 24-hour periods) to be added to dates who's result
includes a daylight savings time adjustment period. Therefore,
while in previous releases <literal>1 day</> and <literal>24
- hours</> where interchangeable interval periods, in this release
+ hours</> were interchangeable interval values, in this release
they are treated differently, e.g.
<programlisting>
'2005-05-03 00:00:00 EST' + '1 day' = '2005-05-04 00:00:00-04'
<listitem>
<para>
Add <function>pg_rotate_logfile()</> to force rotation of the
- server log file (Dave Page,
+ server log file (Dave Page, Andreas Pflug)
</para>
</listitem>
<listitem>
<para>
- Change <literal>pg_stat_*</> views to show TOAST tables (Tom)
+ Change <literal>pg_stat_*</> views to include TOAST tables (Tom)
</para>
</listitem>
<listitem>
<para>
Rename some encodings to be more consistent and to follow
- international standards(Bruce)
+ international standards (Bruce)
</para>
<para>
<itemizedlist>
<para>
Previously only one and two-byte <literal>UTF8</> characters
were supported. This is particularly important for support for
- some Chinese character.
+ some Chinese characters.
</para>
</listitem>
<listitem>
<para>
- Allow the UTF8 encoding to work on Win32 (Magnus)
+ Allow the UTF8 encoding to work on Windows (Magnus)
</para>
<para>
- This is done by mapping UTF8 to the Win32-native UTF16
+ This is done by mapping UTF8 to the Windows-native UTF16
implementation.
+ </para>
</listitem>
</itemizedlist>
<listitem>
<para>
- Move language handlers into the <literal>pg_catalog</> schema
+ Move language handler functions into the <literal>pg_catalog</> schema
</para>
<para>
This makes it easier to drop the public schema if desired.
<listitem>
<para>
- Check function syntax as <command>CREATE FUNCTION</> time,
+ Check function syntax at <command>CREATE FUNCTION</> time,
rather than at runtime (Neil)
</para>
<para>
</para>
<para>
This is a byproduct of the newly added <command>OUT</> and
- <command>INOUT</> functionality.
+ <command>INOUT</> functionality. <command>RETURN</> can
+ be omitted when it is not needed to provide the function result.
</para>
</listitem>
<listitem>
<para>
- Prevent psql <command>\x</> (expanded mode) from affecting other
- backslash output (Neil)
+ Prevent psql <command>\x</> (expanded mode) from affecting
+ backslash-command displays (Neil)
</para>
</listitem>
<listitem>
<para>
- Have psql <command>\d</> show tablespace of indexes (Qingqing
+ Make psql <command>\d</> show tablespaces of indexes (Qingqing
Zhou)
</para>
</listitem>
<para>
This allows the user to just add <command>\h</> to the front of
the syntax error query and get help on the supported syntax.
- Previously any additional query text beyond the help topics
- supported had to be removed to use <command>\h</>.
+ Previously any additional query text beyond the command name
+ had to be removed to use <command>\h</>.
</para>
</listitem>
</para>
<para>
For example, using <literal>C</> locale <literal>100000</> would
- be output as <literal>100,000.0</> and European locale might
+ be output as <literal>100,000.0</> while a European locale might
output this value as <literal>100.000,0</>.
</para>
</listitem>
<listitem>
<para>
- Add Kerberos 5 support for Win32 (Magnus)
+ Add Kerberos 5 support for Windows (Magnus)
</para>
</listitem>
<listitem>
<para>
- Allow libpq to be build thread-safe on Win32 (Dave Page)
+ Allow libpq to be built thread-safe on Windows (Dave Page)
</para>
</listitem>
<listitem>
<para>
- Cleanup the <filename>/contrib/lo</> module (Tom)
+ Clean up the <filename>/contrib/lo</> module (Tom)
</para>
</listitem>
<listitem>
<para>
- <filename>/contrib/pgcrypto</> (Marko Kreen)
+ Improve <filename>/contrib/pgcrypto</> (Marko Kreen)
</para>
<itemizedlist>
implementation of OpenPGP symmetric-key and public-key encryption
</para>
<para>
- Supported are both RSA and Elgamal public-key algorithms.
+ Both RSA and Elgamal public-key algorithms are supported.
</para>
</listitem>
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