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Commita43b4ab

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Fix enforcement of restrictions inside regexp lookaround constraints.
Lookahead and lookbehind constraints aren't allowed to contain backrefs,and parentheses within them are always considered non-capturing. Or sosays the manual. But the regexp parser forgot about these rules onceinside a parenthesized subexpression, so that constructs like (\w)(?=(\1))were accepted (but then not correctly executed --- a case like this actedlike (\w)(?=\w), without any enforcement that the two \w's match the sametext). And in (?=((foo))) the innermost parentheses would be counted ascapturing parentheses, though no text would ever be captured for them.To fix, properly pass down the "type" argument to the recursive invocationof parse().Back-patch to all supported branches; it was agreed that silentmisexecution of such patterns is worse than throwing an error, even thoughnew errors in minor releases are generally not desirable.
1 parent8d7396e commita43b4ab

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3 files changed

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‎src/backend/regex/regcomp.c‎

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Original file line numberDiff line numberDiff line change
@@ -951,7 +951,7 @@ parseqatom(struct vars * v,
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EMPTYARC(lp,s);
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EMPTYARC(s2,rp);
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NOERR();
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atom=parse(v,')',PLAIN,s,s2);
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atom=parse(v,')',type,s,s2);
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assert(SEE(')')||ISERR());
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NEXT();
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NOERR();

‎src/test/regress/expected/regex.out‎

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@@ -490,3 +490,8 @@ select 'a' ~ '()+\1';
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t
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(1 row)
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-- Error conditions
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select 'xyz' ~ 'x(\w)(?=\1)'; -- no backrefs in LACONs
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ERROR: invalid regular expression: invalid backreference number
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select 'xyz' ~ 'x(\w)(?=(\1))';
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ERROR: invalid regular expression: invalid backreference number

‎src/test/regress/sql/regex.sql‎

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Original file line numberDiff line numberDiff line change
@@ -117,3 +117,7 @@ select 'a' ~ '$()|^\1';
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select'a' ~'.. ()|\1';
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select'a' ~'()*\1';
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select'a' ~'()+\1';
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-- Error conditions
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select'xyz' ~'x(\w)(?=\1)';-- no backrefs in LACONs
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select'xyz' ~'x(\w)(?=(\1))';

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