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<appendix id="release">
<title>Release Notes</title>
- <sect1 id="release-devel">
+ <sect1 id="release-7-4">
<title>Release 7.4</title>
<sect2><title>Overview</title>
</footnote>
</para>
-<para> Improved GROUP BY processing by using hash buckets</para>
+<para> Improved GROUP BY processing by using hash buckets
+ <footnote>
+ <para>
+ In previous releases, GROUP BY totals were accumulated by
+ sequentially scanning the list of groups looking for a match;
+ the 7.4 code places GROUP BY values in hash buckets so the
+ proper match can be found much quicker. This is particularly
+ significant in speeding up queries that have a large
+ number of distinct GROUP BY values.
+ </para>
+ </footnote>
+</para>
-<para> New multi-key hash join capability</para>
+<para> New multi-key hash join capability
+ <footnote>
+ <para>
+ In previous releases, hash joins could only occur on single-column
+ joins. This release allows multi-column hash joins.
+ </para>
+ </footnote>
+ </para>
-<para> ANSI joins are now better optimized</para>
+<para> ANSI joins are now better optimized
+ <footnote>
+ <para>
+ Prior releases evaluated ANSI join syntax only in the order
+ specified by the query; 7.4 allows full optimization of
+ queries using ANSI join syntax, meaning the optimizer considers
+ all possible join orderings and chooses the most efficient.
+ </para>
+ </footnote>
+ </para>
-<para> Faster and more powerful regular expression code</para>
+<para> Faster and more powerful regular expression code
+ <footnote>
+ <para>
+ The entire regular expression module has been replaced with a new
+ version by Henry Spencer, originally written for TCL. The code
+ greatly improves performance and supports several flavors
+ of regular expressions.
+ </para>
+ </footnote>
+ </para>
-<para> Function-inlining for simple SQL functions</para></glossdef>
+<para> Function-inlining for simple SQL functions
+ <footnote>
+ <para>
+ Simple SQL functions can now be inlined by including their SQL
+ in the main query. This improves performance by preventing
+ repeated calls to the SQL function --- this allows simple
+ SQL functions to behave like macros.
+ </para>
+ </footnote>
+ </para></glossdef>
</glossentry>
<glossentry> <glossterm> IPv6</glossterm>
<glossdef><para> Full support for IPv6 connections and IPv6 address
-data types</para></glossdef>
+data types
+ <footnote>
+ <para>
+ Prior releases allowed only IPv6 connections and IP data types only
+ supported IPv4 addresses. This release adds full IPv6 support in
+ both of these areas.
+ </para>
+ </footnote>
+ </para></glossdef>
</glossentry>
<glossentry><glossterm> SSL</glossterm>
<glossdef><para> Major improvements in SSL performance and
-reliability</para></glossdef>
+reliability
+ <footnote>
+ <para>
+ Several people very familiar with the SSL API have overhauled our
+ SSL code to improve SSL key negotiation and error recovery.
+ </para>
+ </footnote>
+ </para></glossdef>
</glossentry>
<glossentry><glossterm> Index Growth Prevention</glossterm>
<glossdef><para> Allow free space map to efficiently reuse empty index
-pages, and other free space management improvements.</para></glossdef>
+pages, and other free space management improvements.
+ <footnote>
+ <para>
+ In prior releases, index pages that were left empty because of
+ deleted rows could only be reused by rows with index values similar
+ to the original rows indexed on that page. In 7.4, VACUUM records
+ empty index pages and allows them to be used for any future index
+ rows.
+ </para>
+ </footnote>
+ </para></glossdef>
</glossentry>
<glossentry><glossterm> Standards Compliance</glossterm>
<glossentry><glossterm> Threads</glossterm>
<glossdef><para> libpq and ecpg are now fully thread-safe with
---enable-thread-safety</para></glossdef>
+--enable-thread-safety
+ <footnote>
+ <para>
+ While prior libpq releases already supported threads, this release
+ improves thread safety by fixing some non-thread-safe code that
+ was used in the database connection routines.
+ </para>
+ </footnote>
+ </para></glossdef>
</glossentry>
<glossentry><glossterm> Contrib</glossterm>
<glossdef><para> New version of full text indexing (tsearch2)</para>
-<para> New autovacuum tool</para>
+<para> New autovacuum tool
+ <footnote>
+ <para>
+ This new tool monitors the database statistics tables for
+ INSERT/UPDATE/DELETE activity and automatically vacuums tables when
+ needed.
+ </para>
+ </footnote>
+ </para>
<para> Array handling has been improved and moved into the main
-server</para></glossdef>
+server
+ <footnote>
+ <para>
+ Many array limitations have been removed and they behave more like
+ fully-supported data types.
+ </para>
+ </footnote>
+ </para></glossdef>
</glossentry>
</glosslist></para></sect2>
<para> Observe the following incompatibilities:
<itemizedlist>
<listitem><para> The server-side autocommit setting was removed and reimplemented
- in client applications and languages.</para></listitem>
+ in client applications and languages.
+ <footnote>
+ <para>
+ Server-side autocommit was causing too many problems with
+ languages and applications that wanted to control their own
+ autocommit behavior so autocommit was removed from the server
+ and added to individual client API's as appropriate.
+ </para>
+ </footnote>
+ </para></listitem>
<listitem><para> Error message wording has changed substantially in this release,
and error codes have been added.</para></listitem>
<listitem><para> ANSI inner joins may behave differently because they are now better optimized</para></listitem>
- <listitem><para> A number of server variables have been renamed for clarity</para></listitem>
- <listitem><para> MOVE/FETCH 0 now does nothing</para></listitem>
+ <listitem><para> A number of server variables have been renamed for
+ clarity, primarily those related to logging</para></listitem>
+ <listitem><para> MOVE/FETCH 0 now does nothing
+ <footnote>
+ <para>
+ In prior releases, FETCH 0 would fetch all remaining rows, and
+ MOVE 0 would move to the end of the cursor.
+ </para>
+ </footnote>
+ </para></listitem>
<listitem><para> MOVE/FETCH now returns the actual number of rows moved/fetched, or zero
- if at the beginning/end of the cursor</para></listitem>
- <listitem><para> COPY now can process carriage-return/line-feed and carriage-return
- terminated files. Literal carriage-returns and line-feeds are no
+ if at the beginning/end of the cursor
+ <footnote>
+ <para>
+ Prior releases would return the tuple count passed to the
+ command, not the actual number of rows FETCHed or MOVEd.
+ </para>
+ </footnote>
+ </para></listitem>
+ <listitem><para> COPY now can process carriage-return and
+ carriage-return/line-feed end-of-line terminated files.</para></listitem>
+ <listitem><para>Literal carriage-returns and line-feeds are no
longer accepted as data values; use \r and \n instead.</para></listitem>
<listitem><para> Trailing spaces are now trimmed when converting
from <type>CHAR(n)</type> to
<type>VARCHAR(n)</type> / <type>TEXT</type></para></listitem>
<listitem><para> <function>FLOAT(p)</function> now measures 'p' in bits, not digits</para></listitem>
- <listitem><para> Ambiguous date values now must match the ordering specified by DateStyle</para></listitem>
+ <listitem><para> Ambiguous date values now must match the ordering specified by DateStyle
+ <footnote>
+ <para>
+ In prior releases, a date of <literal>10/20/03</> was
+ interpreted as a date in October even if the
+ <varname>DateStyle</> specified the day should be first. In
+ 7.4, <varname>DateStyle</> is honored when converting such
+ values and will throw an error if the date is invalid for the
+ current <varname>DateStyle</>.
+ </para>
+ </footnote>
+ </para></listitem>
<listitem><para> The <function>oidrand()</function>, <function>oidsrand()</function>,
- and <function>userfntest()</function> functions have been removed.</para></listitem>
+ and <function>userfntest()</function> functions have been removed.
+ <footnote>
+ <para>
+ These functions were determined to be no longer useful.
+ </para>
+ </footnote>
+ </para></listitem>
<listitem><para> <literal>'now'</literal> will no longer work as a column default; <function>now()</> or
- <function>CURRENT_TIMESTAMP</> should be used instead</para></listitem>
+ <function>CURRENT_TIMESTAMP</> should be used instead
+ <footnote>
+ <para>
+ In prior releases, there was special code so the string
+ <literal>'now'</literal> was interpreted at
+ <command>INSERT</> time and not at table creation time, but
+ this work around didn't cover all cases. Release 7.4
+ now requires that defaults be defined properly using the
+ <function>now()</> or the special value
+ <function>CURRENT_TIMESTAMP</>. These will work in all
+ situations.
+ </para>
+ </footnote>
+ </para></listitem>
<listitem><para> <literal>'today'</literal> will no longer work as a column default; <function>CURRENT_DATE</>
- should be used instead</para></listitem>
+ should be used instead
+ <footnote>
+ <para>
+ Same description as above.
+ </para>
+ </footnote>
+ </para></listitem>
<listitem><para> Dollar sign (<literal>$</>) is no longer allowed in operator names</para></listitem>
- <listitem><para> Dollar sign (<literal>$</>) can be a non-first character in identifiers</para></listitem>
+ <listitem><para> Dollar sign (<literal>$</>) can be a non-first character in identifiers
+ <footnote>
+ <para>
+ This was done to improve compatibility with other database
+ systems.
+ </para>
+ </footnote>
+ </para></listitem>
</itemizedlist></para></sect2>
<sect2> <title> Changes </title>
<itemizedlist>
<listitem><para>Allow IPv6 server connections (Nigel Kukard, Johan Jordaan, Bruce, Tom, Kurt
Roeckx, Andrew Dunstan)</para></listitem>
-<listitem><para>Fix SSL to handle errors cleanly (Nathan Mueller)</para></listitem>
+<listitem><para>Fix SSL to handle errors cleanly (Nathan Mueller)
+ <footnote>
+ <para>
+ In prior releases,
+ </para>
+ </footnote>
+ </para></listitem>
<listitem><para>SSL protocol security and performance improvements (Sean Chittenden)</para></listitem>
<listitem><para>Print lock information when a deadlock is detected (Tom)</para></listitem>
<listitem><para>Update <filename>/tmp</filename> socket mod. times regularly to avoid their removal (Tom)</para></listitem>
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