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Commit1925ac2

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Fix misbehavior in contrib/pg_trgm with an unsatisfiable regex.
If the regex compiler can see that a regex is unsatisfiable(for example, '$foo') then it may emit an NFA having no arcs.pg_trgm's packGraph function did the wrong thing in this case;it would access off the end of a work array, and with bad luckcould produce a corrupted output data structure causing moreproblems later. This could end with wrong answers or crashesin queries using a pg_trgm GIN or GiST index with such a regex.Fix by not trying to de-duplicate if there aren't at least 2 arcs.Per bug #17830 from Alexander Lakhin. Back-patch to all supportedbranches.Discussion:https://postgr.es/m/17830-57ff5f89bdb02b09@postgresql.org
1 parentd66bb04 commit1925ac2

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3 files changed

+25
-10
lines changed

3 files changed

+25
-10
lines changed

‎contrib/pg_trgm/expected/pg_word_trgm.out

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1044,3 +1044,9 @@ select t,word_similarity('Kabankala',t) as sml from test_trgm2 where t %> 'Kaban
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Waikala | 0.3
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(89 rows)
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1047+
-- test unsatisfiable pattern
1048+
select * from test_trgm2 where t ~ '.*$x';
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t
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---
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(0 rows)
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‎contrib/pg_trgm/sql/pg_word_trgm.sql

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -43,3 +43,6 @@ select t,word_similarity('Baykal',t) as sml from test_trgm2 where 'Baykal' <% t
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select t,word_similarity('Kabankala',t)as smlfrom test_trgm2where'Kabankala'<% torder by smldesc, t;
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select t,word_similarity('Baykal',t)as smlfrom test_trgm2where t %>'Baykal'order by smldesc, t;
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select t,word_similarity('Kabankala',t)as smlfrom test_trgm2where t %>'Kabankala'order by smldesc, t;
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-- test unsatisfiable pattern
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select*from test_trgm2where t ~'.*$x';

‎contrib/pg_trgm/trgm_regexp.c

Lines changed: 16 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -1947,9 +1947,7 @@ packGraph(TrgmNFA *trgmNFA, MemoryContext rcontext)
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arcsCount;
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HASH_SEQ_STATUSscan_status;
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TrgmState*state;
1950-
TrgmPackArcInfo*arcs,
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*p1,
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*p2;
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TrgmPackArcInfo*arcs;
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TrgmPackedArc*packedArcs;
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TrgmPackedGraph*result;
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inti,
@@ -2021,17 +2019,25 @@ packGraph(TrgmNFA *trgmNFA, MemoryContext rcontext)
20212019
qsort(arcs,arcIndex,sizeof(TrgmPackArcInfo),packArcInfoCmp);
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20232021
/* We could have duplicates because states were merged. Remove them. */
2024-
/* p1 is probe point, p2 is last known non-duplicate. */
2025-
p2=arcs;
2026-
for (p1=arcs+1;p1<arcs+arcIndex;p1++)
2022+
if (arcIndex>1)
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{
2028-
if (packArcInfoCmp(p1,p2)>0)
2024+
/* p1 is probe point, p2 is last known non-duplicate. */
2025+
TrgmPackArcInfo*p1,
2026+
*p2;
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2028+
p2=arcs;
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for (p1=arcs+1;p1<arcs+arcIndex;p1++)
20292030
{
2030-
p2++;
2031-
*p2=*p1;
2031+
if (packArcInfoCmp(p1,p2)>0)
2032+
{
2033+
p2++;
2034+
*p2=*p1;
2035+
}
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}
2037+
arcsCount= (p2-arcs)+1;
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}
2034-
arcsCount= (p2-arcs)+1;
2039+
else
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arcsCount=arcIndex;
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/* Create packed representation */
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result= (TrgmPackedGraph*)

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