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<sect1 id="release-9-0">

defaulted to off for many years (Tom Lane)

</para>

</listitem>

<listitem>

<para>

Remove server variable <varname>regex_flavor</>, which

(e.g. Perl-regex compatible) for many years (Tom Lane)

</para>

</listitem>

</itemizedlist>

</sect3>

<sect3>

<listitem>

<para>

Fix <link linkend="functions-similarto-regexp"><literal>SIMILAR

TO</></link> to match the SQL standard-specified behavior

by processing <literal>?</> and <literal>{}</> the same way

they are processed in regular expressions (Tom Lane)

</para>

</listitem>

<listitem>

<para>

Properly treat <literal>^</> and <literal>$</> as literals in

<literal>SIMILAR TO</> patterns, to match the SQL standard (Tom Lane)

</para>

<para>

Previously these were treated using regular expression syntax. This

change breaks backward compatibility. This also affects

<function>substring()</>'s interpretation of regular expressions.

</para>

</listitem>

<listitem>

<para>

Process parentheses as literals in <literal>SIMILAR TO</> expressions;

also make character class handling more standards-compliant (Tom Lane)

Improve standards compliance of <link

linkend="functions-similarto-regexp"><literal>SIMILAR TO</></link>

patterns and SQL-style <function>substring()</> patterns (Tom Lane)

</para>

<para>

This also affects <function>substring()</>'s handling of regular

expressions.

This includes treating <literal>?</> and <literal>{...}</> as

pattern metacharacters, while they were simple literal characters

before; that corresponds to new features added in SQL:2008.

Also, <literal>^</> and <literal>$</> are now treated as simple

literal characters; formerly they were treated as metacharacters,

as if the pattern were following POSIX rather than SQL rules.

Also, in SQL-standard <function>substring()</>, use of parentheses

for nesting no longer interferes with capturing of a substring.

Also, processing of bracket expressions (character classes) is

now more standards-compliant.

</para>

</listitem>

<listitem>

<para>

Do not allow <link

linkend="functions-string-sql"><function>substring()</></link>

to have a negative third length, per the SQL standard (Tom Lane)

Reject negative length values in 3-parameter <link

linkend="functions-string-sql"><function>substring()</></link>

for bit strings, per the SQL standard (Tom Lane)

</para>

</listitem>

<listitem>

<para>

Install server-side language PL/pgSQL by default (Bruce Momjian)

Install server-side language PL/pgSQL by default (Bruce Momjian)

</para>

</listitem>