-<!-- $PostgreSQL: pgsql/doc/src/sgml/release.sgml,v 1.543 2007/11/17 15:17:16 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/release.sgml,v 1.544 2007/11/17 21:13:42 momjian Exp $ -->
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<listitem>
<para>
- Asynchronous commit delays writes to WAL for committed transactions
+ Asynchronous commit delays writes to WAL during transaction commit
</para>
</listitem>
<listitem>
<para>
- Distributed checkpoints prevent I/O spikes during checkpoints
+ Distributed checkpoints prevent checkpoint I/O spikes
</para>
</listitem>
<listitem>
<para>
- Prevent large sequential scans from forcing out more frequently
- used cached pages
+ Prevent large sequential scans from forcing out more frequently used
+ cached pages
</para>
</listitem>
<listitem>
<para>
- Reduce need for vacuum by using pseudo-transaction ids in
+ Reduce need for vacuum by using non-persistent transaction ids for
read-only transactions
</para>
</listitem>
<itemizedlist>
- <listitem>
- <para>
- <filename>contrib/tsearch2</> features have been moved into
- the core server, with some minor syntax changes
- </para>
-
- <para>
- <filename>contrib/tsearch2</> now contains a compatibility
- interface.
- </para>
- </listitem>
-
<listitem>
<para>
Non-character values are no longer automatically cast to
<para>
Previously, a function or operator that took a <type>TEXT</>
- parameter used to automatically cast a non-<type>TEXT</> value to
- <type>TEXT</> and call the function or operator, if needed. This
- no longer happens and an explicit cast to <type>TEXT</> is now
- required. For example, these expressions now throw an error:
-
-<programlisting>
-substr(current_date, 1, 1);
-23 LIKE '%2%'
-5.4 ~ '6';
-</programlisting>
-
- but these work because of the explicit casts:
+ parameter automatically cast a non-<type>TEXT</> value to
+ <type>TEXT</>, if needed. This no longer happens and an explicit
+ cast to <type>TEXT</> is now required. For example, these
+ expressions now require a cast to TEXT:
<programlisting>
substr(current_date::text, 1, 1);
</para>
</listitem>
+ <listitem>
+ <para>
+ Full text search features from <filename>contrib/tsearch2</> have
+ been moved into the core server, with some minor syntax changes
+ </para>
+
+ <para>
+ <filename>contrib/tsearch2</> now contains a compatibility
+ interface.
+ </para>
+ </listitem>
+
<listitem>
<para>
Numerous changes in administrative server parameters
<para>
<literal>ORDER BY ... USING</> <replaceable>operator</> now must
use a less-than or greater-than <replaceable>operator</> that is
- defined in a btree operator class (???)
+ defined in a btree operator class
</para>
<para>
The old naming convention is still honored when possible, but
client code should no longer depending on it. Application code
should use the new <literal>pg_type.typarray</literal> column to
- determine the array data type.
+ determine the array's data type.
</para>
</listitem>
<listitem>
<para>
<command>SET LOCAL</command> changes now persist until
- the end of the top-most transaction, unless rolled back (Tom)
+ the end of the outer-most transaction, unless rolled back (Tom)
</para>
<para>
- Previously <command>SET LOCAL</command>'s effects reverted
- during subtransaction commit and <command>RELEASE</>.
+ Previously <command>SET LOCAL</command>'s effects were lost
+ after subtransaction commit or <command>RELEASE</>.
</para>
</listitem>
</para>
<para>
- For example, <literal>BEGIN; DROP DATABASE; COMMIT</> will now be
+ For example, <literal>"BEGIN; DROP DATABASE; COMMIT"</> will now be
rejected even if submitted as a single query message.
</para>
</listitem>
</para>
<para>
- In UTF8-encoded databases the argument is now processed as a Unicode
- code point. In other multi-byte encodings the argument must designate
- a 7-bit ASCII character, or an error is raised. Zero also causes an
- error. <function>ascii()</function> has been adjusted as well to
- match this behavior.
+ In UTF8-encoded databases the <function>chr()</function> argument is
+ now processed as a Unicode code point. In other multi-byte encodings
+ <function>chr()</function>'s argument must designate a 7-bit ASCII
+ character. Zero is no longer a valid parameter.
+ <function>ascii()</function> has been adjusted similarly.
</para>
</listitem>
<para>
<function>convert_from(bytea, name)</function> returns
<type>TEXT</> — converts the first argument from the named
- encoding to the database encoding.
+ encoding to the database encoding
</para>
</listitem>
<para>
<function>convert_to(text, name)</function> returns
<type>BYTEA</> — converts the first argument from the
- database encoding to the named encoding.
+ database encoding to the named encoding
</para>
</listitem>
<para>
<function>length(bytea, name)</function> returns
<type>INTEGER</> — gives the length of the first
- argument in characters in the named encoding.
+ argument in characters in the named encoding
</para>
</listitem>
</itemizedlist>
<listitem>
<para>
<command>ROLLBACK</> outside a multi-statement transaction now
- issues a <literal>NOTICE</> instead of <literal>WARNING</> (Bruce)
- (Tom)
+ issues <literal>NOTICE</> instead of <literal>WARNING</> (Bruce)
</para>
</listitem>
</para>
<para>
- The new <function>SET_VARSIZE()</> macro <emphasis>must</> be
- used to set the length of generated values. Also, it might be
- necessary to expand (<quote>de-TOAST</quote>) input values in
- additional places.
+ The new <function>SET_VARSIZE()</> macro <emphasis>must</> be used
+ to set the length of generated <type>varlena</> values. Also, it
+ might be necessary to expand (<quote>de-TOAST</quote>) input values
+ in more cases.
</para>
</listitem>
<listitem>
<para>
- Asynchronous commit delays writes to WAL for committed transactions
+ Asynchronous commit delays writes to WAL during transaction commit
(Simon)
</para>
<para>
This feature dramatically increases performance for data-modifying
- queries. The disadvantage is that because on-disk changes are
+ queries. The disadvantage is that because disk writes are
delayed, if the operating system crashes before data is written to
- the disk, committed data will be lost. This is useful only for
+ the disk, committed data will be lost. This feature is useful for
applications that can accept some data loss. Unlike
<varname>fsync</varname>, asynchronous commit does not risk database
- corruption; the worst case is that after an operating system crash
- the last few reportedly-committed transactions will be missing.
- This feature is enabled turning <varname>synchronous_commit</>
+ consistency; the worst case is that after an operating system crash
+ the last few reportedly-committed transactions might be missing.
+ This feature is enabled by turning <varname>synchronous_commit</>
<literal>off</> and setting <varname>wal_writer_delay</>.
</para>
</listitem>
<listitem>
<para>
- Distributed checkpoints prevent I/O spikes during
- checkpoints (Itagaki Takahiro and Heikki Linnakangas)
+ Distributed checkpoints prevent checkpoint I/O spikes (Itagaki
+ Takahiro and Heikki Linnakangas)
</para>
<para>
- Previously all modified buffers were forced to disk at
- checkpoint time, causing an I/O spike and decreasing server
- performance. This new capability spreads checkpoint activity out
- between checkpoints, reducing peak I/O usage. (User-requested
- and shutdown checkpoints are still immediately written to disk.)
+ Previously all modified buffers were forced to disk during
+ checkpoints, causing an I/O spike and decreasing server performance.
+ This new capability spreads disk writes out between checkpoints,
+ reducing peak I/O usage. (User-requested and shutdown checkpoints
+ are still written immediately to disk.)
</para>
</listitem>
</para>
<para>
- To allow high concurrency <command>UPDATE</> creates a new tuple,
- rather than replacing the old tuple. Previously only
+ To allow high concurrency <command>UPDATE</>, creates a new tuple
+ rather than overwriting the old tuple. Previously only
<command>VACUUM</> could reuse space taken by old tuples. With
<acronym>HOT</> dead tuple space can be reused at the time of
<command>UPDATE</> or <command>INSERT</>. This allows for more
consistent performance. <acronym>HOT</> even allows deleted row
- space reuse. <acronym>HOT</> space reuse is not possible if
- <command>UPDATE</> changes indexed columns.
+ space reuse. <acronym>HOT</> space reuse is not possible for
+ <command>UPDATE</>s that change indexed columns.
</para>
</listitem>
<para>
Variable-length data types with data values less then 128 bytes
- will see a decrease of 3-6 bytes. For example, two
- <type>CHAR(1)</type> fields now take 4 bytes instead of 16. Rows
+ will see a storage decrease of 3-6 bytes. For example, two
+ <type>CHAR(1)</type> fields now use 4 bytes instead of 16. Rows
are also 4 bytes shorter.
</para>
</listitem>
<listitem>
<para>
- Reduce need for vacuum by using pseudo-transaction ids in
+ Reduce need for vacuum by using non-persistent transaction ids for
read-only transactions (Florian Pflug)
</para>
<para>
- Pseudo-transaction ids do not increment the global transaction
- counter. Therefore, they do not add to the need for vacuum to
- read all database rows to prevent problems with transaction id
- wrap-around. Other transaction performance improvements were also
- made that should improve concurrency.
+ Non-persistent transaction ids do not increment the global
+ transaction counter. Therefore, they do not add to the need for
+ vacuum to read all database rows to prevent problems with
+ transaction id wrap-around. Other transaction performance
+ improvements were also made that should improve concurrency.
</para>
</listitem>
</para>
<para>
- Unless WAL archiving is enabled, it is possible to just
- <function>fsync()</> the table at the end of the command,
- increasing performance. Additional WAL efficiencies were also
- made.
+ Unless WAL archiving is enabled, the system now avoids WAL writes
+ for <command>CLUSTER</command> and just <function>fsync()</>s the
+ table at the end of the command. It also does the same for
+ <command>COPY</command> if the table was created in the same
+ transaction. Additional WAL efficiencies for these commands were
+ also made.
</para>
</listitem>
<para>
This is accomplished by starting the new sequential scan in the
- middle of the table (where the other sequential scan is already
+ middle of the table (where another sequential scan is already
in-progress) and wrapping around to the beginning to finish. This
- may affect the order of returned rows in a non-<literal>ORDER BY</>
+ can affect the order of returned rows in a non-<literal>ORDER BY</>
query.
</para>
</listitem>
<para>
This is done by sequentially scanning the table and using a filter
to save the few requested rows, rather than sorting the entire
- table. This is used if there is no matching index.
+ table. This is useful if there is no matching index.
</para>
</listitem>
<title>Server Changes</title>
<itemizedlist>
+ <listitem>
+ <para>
+ Autovacuum is now enabled by default (Alvaro)
+ </para>
+ </listitem>
+
<listitem>
<para>
Support multiple concurrent autovacuum processes (Alvaro, Itagaki
</para>
<para>
- This allows multiple vacuums to run concurrently, meaning
- vacuuming of a large table will not prevent smaller tables from
- being vacuumed at the same time. Autovacuum is now considered
- mature and thus enabled by default. Several autovacuum
- default parameter values were also updated.
+ This allows multiple vacuums to run concurrently. This prevents
+ vacuuming of a large table from delaying the vacumming of smaller
+ tables. Several autovacuum parameter defaults were also modified.
</para>
</listitem>
<listitem>
<para>
- Autovacuum is now enabled by default (Alvaro)
- </para>
-
- <para>
- Also, autovacuum now reports its activity start time in
+ Autovacuum now reports its activity start time in
<literal>pg_stat_activity</literal> (Tom)
</para>
</listitem>
</para>
<para>
- This should be used in place of the native Kerberos authentication
- because it is an industry standard.
+ This should be preferred to native Kerberos authentication because
+ GSSAPI is an industry standard.
</para>
</listitem>
</para>
<para>
- JOHAB cannot safely be used as a server-side encoding.
+ JOHAB is not safe as a server-side encoding.
</para>
</listitem>
<listitem>
<para>
- Allow logfile creation in CSV format (Arul Shaji, Greg Smith,
- Andrew Dunstan)
+ Allow server log output in comma-separated value (CSV) format (Arul
+ Shaji, Greg Smith, Andrew Dunstan)
</para>
<para>
<listitem>
<para>
Add <varname>log_autovacuum_min_duration</varname> parameter to
- support configurable logging of autovacuum actions (Simon, Alvaro)
+ support configurable logging of autovacuum activity (Simon, Alvaro)
</para>
</listitem>
<listitem>
<para>
- Add <varname>log_lock_waits</varname> parameter to log long wait
- times (Simon)
+ Add <varname>log_lock_waits</varname> parameter to log lock waiting
+ (Simon)
</para>
</listitem>
<listitem>
<para>
- Add <varname>log_temp_files</varname> parameter to log usage of
- temporary files (Bill Moran)
+ Add <varname>log_temp_files</varname> parameter to log temporary
+ file usage (Bill Moran)
</para>
</listitem>
<listitem>
<para>
- <varname>log_line_prefix</varname> escapes <literal>%s</literal>
- and <literal>%c</literal> can now be used in all processes
- (Andrew)
+ <varname>log_line_prefix</varname> now supports
+ <literal>%s</literal> and <literal>%c</literal> escapes in all
+ processes (Andrew)
+ </para>
+
+ <para>
+ Previously these escapes worked only for user sessions, not for
+ database helper processes.
</para>
</listitem>
<listitem>
<para>
- Use our own timezone support for formatting timestamps displayed in
- the server log (Tom)
+ Use PostgreSQL-supplied timezone support for formatting timestamps
+ displayed in the server log (Tom)
</para>
<para>
</para>
<para>
- Previously setting <varname>archive_command</> to an empty
- string turned off archiving. Now <varname>archive_mode</> turns
- archiving on and off. This is useful for stopping archiving
- temporarily.
+ Previously setting <varname>archive_command</> to an empty string
+ turned off archiving. Now <varname>archive_mode</> turns archiving
+ on and off, independent of <varname>archive_command</>. This is
+ useful for stopping archiving temporarily.
</para>
</listitem>
<listitem>
<para>
- Add <varname>log_restartpoints</varname> archive recovery option
- to emit a log message at each recovery restart point (Simon)
+ Add <varname>log_restartpoints</varname> to control logging of
+ every point-in-time recovery restart point (Simon)
</para>
</listitem>
</para>
<para>
- This parameters allows a list of tablespaces to be specified
- which enables spreading the I/O load across multiple
- tablespaces. A random tablespace is chosen each time a temporary
- object is created. Temporary files are not stored in
- per-database <filename>pgsql_tmp/</filename> directories anymore
- but in per-tablespace directories.
+ This parameters supports a list of tablespaces to be used. This
+ enables spreading the I/O load across multiple tablespaces. A random
+ tablespace is chosen each time a temporary object is created.
+ Temporary files are no longer stored in per-database
+ <filename>pgsql_tmp/</filename> directories but in per-tablespace
+ directories.
</para>
</listitem>
<listitem>
<para>
New system view <literal>pg_stat_bgwriter</literal> displays
- statistics about the background writer activity (Magnus)
+ statistics about background writer activity (Magnus)
</para>
</listitem>
<listitem>
<para>
- Add an <literal>xact_start</literal> column to
+ Add an <literal>xact_start</literal> (transaction start time) column to
<literal>pg_stat_activity</literal> (Neil)
</para>
</para>
<para>
- We now always start the collector process, unless prevented by a
- problem with setting up the stats UDP socket.
+ We now always start the collector process, unless <acronym>UDP</>
+ socket creation fails.
</para>
</listitem>
<listitem>
<para>
Merge <varname>stats_block_level</> and <varname>stats_row_level</>
- parameters into a single parameter <varname>track_counts</>,
- which controls all messages sent to the collector process (Tom)
+ parameters into a single parameter <varname>track_counts</>, which
+ controls all messages sent to the statistics collector process
+ (Tom)
</para>
</listitem>
<para>
Previously, dropping (or attempting to drop) a user who owned many
- objects could result in extremely large <literal>NOTICE</literal> or
+ objects could result in large <literal>NOTICE</literal> or
<literal>ERROR</literal> messages listing all these objects; this
caused problems for some client applications. The length of the
list is now limited, although a full list is still sent to the
</para>
<para>
- This allows low-level code to recognize that these tables are
- temporary, which enables various optimizations such as not
- WAL-logging changes and using local rather than shared buffers
- for access. This also fixes a bug where backends unexpectedly
- held open file references to temporary tables.
+ This allows low-level code to recognize these tables as temporary,
+ which enables various optimizations such as not WAL-logging changes
+ and using local rather than shared buffers for access. This also
+ fixes a bug where backends unexpectedly held open file references
+ to temporary tables.
</para>
</listitem>
<para>
Fix problem that a constant flow of new connection requests could
indefinitely delay the postmaster from completing a shutdown or
- crash restart (Tom)
+ a crash restart (Tom)
</para>
</listitem>
<listitem>
<para>
- Add Kerberos realm specification, <varname>krb_realm</> (Magnus)
+ Add a Kerberos realm parameter, <varname>krb_realm</> (Magnus)
</para>
</listitem>
projects / postgresql.git / commitdiff