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Commit05d2497

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Improve similar_escape() in two different ways:
* Stop escaping ? and {. As of SQL:2008, SIMILAR TO is defined to havePOSIX-compatible interpretation of ? as well as {m,n} and related constructs,so we should allow these things through to our regex engine.* Escape ^ and $. It appears that our regex engine will treat ^^ at thebeginning of the string the same as ^, and similarly for $$ at the end ofthe string, which meant that SIMILAR TO was effectively ignoring ^ at thestart of the pattern and $ at the end. Since these are not supposed to bemetacharacters, this is a bug.The second part of this is arguably a back-patchable bug fix, but I'mhesitant to do that because it might break applications that are expectingsomething like "col SIMILAR TO '^foo$'" to work like a POSIX pattern.Seems safer to only change it at a major version boundary.Per discussion of an example from Doug Gorley.
1 parent8a5849b commit05d2497

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2 files changed

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2 files changed

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‎doc/src/sgml/func.sgml

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<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.488 2009/10/09 21:02:55 petere Exp $ -->
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<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.489 2009/10/10 03:50:15 tgl Exp $ -->
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<chapter id="functions">
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<title>Functions and Operators</title>
@@ -3154,6 +3154,31 @@ cast(-44 as bit(12)) <lineannotation>111111010100</lineannotation>
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or more times.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>?</literal> denotes repetition of the previous item zero
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or one time.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>{</><replaceable>m</><literal>}</literal> denotes repetition
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of the previous item exactly <replaceable>m</> times.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>{</><replaceable>m</><literal>,}</literal> denotes repetition
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of the previous item <replaceable>m</> or more times.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>{</><replaceable>m</><literal>,</><replaceable>n</><literal>}</>
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denotes repetition of the previous item at least <replaceable>m</> and
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not more than <replaceable>n</> times.
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</para>
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</listitem>
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<listitem>
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<para>
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Parentheses <literal>()</literal> can be used to group items into
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</listitem>
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</itemizedlist>
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Notice that bounded repetition operators (<literal>?</> and
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<literal>{...}</>) are not provided, though they exist in POSIX.
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Also, the period (<literal>.</>) is not a metacharacter.
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Notice that the period (<literal>.</>) is not a metacharacter
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for <function>SIMILAR TO</>.
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</para>
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<para>

‎src/backend/utils/adt/regexp.c

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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/utils/adt/regexp.c,v 1.82 2009/06/11 14:49:04 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/utils/adt/regexp.c,v 1.83 2009/10/10 03:50:15 tgl Exp $
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*
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*Alistair Crooks added the code for the regex caching
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*agc - cached the regular expressions used - there's a good chance
@@ -639,7 +639,7 @@ textregexreplace(PG_FUNCTION_ARGS)
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/*
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* similar_escape()
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* Convert aSQL99 regexp pattern to POSIX style, so it can be used by
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* Convert aSQL:2008 regexp pattern to POSIX style, so it can be used by
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* our regexp engine.
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*/
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Datum
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}
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elseif (pchar=='_')
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*r++='.';
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elseif (pchar=='\\'||pchar=='.'||pchar=='?'||
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pchar=='{')
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elseif (pchar=='\\'||pchar=='.'||
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pchar=='^'||pchar=='$')
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{
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*r++='\\';
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*r++=pchar;

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