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Fix the general case of quantified regex back-references.

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Cases where a back-reference is part of a larger subexpression that
is quantified have never worked in Spencer's regex engine, because
he used a compile-time transformation that neglected the need to
check the back-reference match in iterations before the last one.
(That was okay for capturing parens, and we still do it if the
regex has *only* capturing parens ... but it's not okay for backrefs.)

To make this work properly, we have to add an "iteration" node type
to the regex engine's vocabulary of sub-regex nodes.  Since this is a
moderately large change with a fair risk of introducing new bugs of its
own, apply to HEAD only, even though it's a fix for a longstanding bug.
This commit is contained in:
Tom Lane
2012-02-24 01:40:18 -05:00
parent 0c9e5d5e0d
commit 173e29aa5d
6 changed files with 884 additions and 55 deletions
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8
src/test/regress/sql/regex.sql
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@ -11,3 +11,11 @@ select 'ccc' ~ '^([bc])\1*$' as t;
select 'xxx' ~ '^([bc])\1*$' as f;
select 'bbc' ~ '^([bc])\1*$' as f;
select 'b' ~ '^([bc])\1*$' as t;
-- Test quantified backref within a larger expression
select 'abc abc abc' ~ '^(\w+)( \1)+$' as t;
select 'abc abd abc' ~ '^(\w+)( \1)+$' as f;
select 'abc abc abd' ~ '^(\w+)( \1)+$' as f;
select 'abc abc abc' ~ '^(.+)( \1)+$' as t;
select 'abc abd abc' ~ '^(.+)( \1)+$' as f;
select 'abc abc abd' ~ '^(.+)( \1)+$' as f;