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Commit3694b4d

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Fix incorrect search for "x?" style matches in creviterdissect().
When the number of allowed iterations is limited (either a "?" quantifieror a bound expression), the last sub-match has to reach to the end of thetarget string. The previous coding here first tried the shortest possiblematch (one character, usually) and then gave up and back-tracked if thatdidn't work, typically leading to failure to match overall, as shown inbug #11478 from Christoph Berg. The minimum change to fix that would be tonot decrement k before "goto backtrack"; but that would be a pretty stupidsolution, because we'd laboriously try each possible sub-match lengthbefore finally discovering that only ending at the end can work. Instead,force the sub-match endpoint limit up to the end for even the firstshortest() call if we cannot have any more sub-matches after this one.Bug introduced in my rewrite that added the iterdissect logic, commit173e29a. The shortest-first search codewas too closely modeled on the longest-first code, which hasn't got thisissue since it tries a match reaching to the end to start with anyway.Back-patch to all affected branches.
1 parenta564307 commit3694b4d

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‎src/backend/regex/regexec.c

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@@ -1190,6 +1190,10 @@ creviterdissect(struct vars * v,
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(k >=min_matches||min_matches-k<end-limit))
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limit++;
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/* if this is the last allowed sub-match, it must reach to the end */
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if (k >=max_matches)
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limit=end;
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/* try to find an endpoint for the k'th sub-match */
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endpts[k]=shortest(v,d,endpts[k-1],limit,end,
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(chr**)NULL, (int*)NULL);

‎src/test/regress/expected/regex.out

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@@ -188,3 +188,11 @@ select regexp_matches('Programmer', '(\w)(.*?\1)', 'g');
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{m,m}
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(2 rows)
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-- Test for proper matching of non-greedy iteration (bug #11478)
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select regexp_matches('foo/bar/baz',
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'^([^/]+?)(?:/([^/]+?))(?:/([^/]+?))?$', '');
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regexp_matches
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----------------
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{foo,bar,baz}
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(1 row)
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‎src/test/regress/sql/regex.sql

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Original file line numberDiff line numberDiff line change
@@ -46,3 +46,7 @@ select 'a' ~ '((((((a+|)+|)+|)+|)+|)+|)';
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-- https://core.tcl.tk/tcl/tktview/6585b21ca8fa6f3678d442b97241fdd43dba2ec0
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select'Programmer' ~'(\w).*?\1'as t;
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select regexp_matches('Programmer','(\w)(.*?\1)','g');
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-- Test for proper matching of non-greedy iteration (bug #11478)
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select regexp_matches('foo/bar/baz',
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'^([^/]+?)(?:/([^/]+?))(?:/([^/]+?))?$','');

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