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Commitbc436e4

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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 parent866fd00 commitbc436e4

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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

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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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-- test unsatisfiable pattern
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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

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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
@@ -1929,9 +1929,7 @@ packGraph(TrgmNFA *trgmNFA, MemoryContext rcontext)
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arcsCount;
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HASH_SEQ_STATUSscan_status;
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TrgmState*state;
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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,
@@ -2003,17 +2001,25 @@ packGraph(TrgmNFA *trgmNFA, MemoryContext rcontext)
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qsort(arcs,arcIndex,sizeof(TrgmPackArcInfo),packArcInfoCmp);
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/* We could have duplicates because states were merged. Remove them. */
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/* p1 is probe point, p2 is last known non-duplicate. */
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p2=arcs;
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for (p1=arcs+1;p1<arcs+arcIndex;p1++)
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if (arcIndex>1)
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{
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if (packArcInfoCmp(p1,p2)>0)
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/* p1 is probe point, p2 is last known non-duplicate. */
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TrgmPackArcInfo*p1,
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*p2;
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p2=arcs;
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for (p1=arcs+1;p1<arcs+arcIndex;p1++)
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{
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p2++;
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*p2=*p1;
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if (packArcInfoCmp(p1,p2)>0)
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{
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p2++;
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*p2=*p1;
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}
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}
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arcsCount= (p2-arcs)+1;
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}
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arcsCount= (p2-arcs)+1;
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else
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arcsCount=arcIndex;
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/* Create packed representation */
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result= (TrgmPackedGraph*)

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