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Commit1dffabe

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Further fix pg_trgm's extraction of trigrams from regular expressions.
Commit9e43e87 turns out to have been insufficient: not only is itnecessary to track tentative parent links while considering a set ofarc removals, but it's necessary to track tentative flag additionsas well. This is because we always merge arc target states intoarc source states; therefore, when considering a merge of the finalstate with some other, it is the other state that will acquire a newTSTATE_FIN bit. If there's another arc for the same color trigramthat would cause merging of that state with the initial state, wefailed to recognize the problem. The test cases for the prior commitevidently only exercised situations where a tentative merge with theinitial state occurs before one with the final state. If it goes theother way around, we'll happily merge the initial and final states,either producing a broken final graph that would never match anything,or triggering the Assert added by the prior commit.It's tempting to consider switching the merge direction when the mergeinvolves the final state, but I lack the time to analyze that idea indetail. Instead just keep track of the flag changes that would resultfrom proposed merges, in the same way that the prior commit trackedproposed parent links.Along the way, add some more debugging support, because I'm not entirelyconfident that this is the last bug here. And tweak matters so thatthe transformed.dot file uses small integers rather than pointer valuesto identify states; that makes it more readable if you're just eyeballingit rather than fooling with Graphviz. And rename a couple of identicallynamed struct fields to reduce confusion.Per report from Corey Csuhta. Add a test case based on his example.(Note: this case does not trigger the bug under 9.3, apparently becauseits different measurement of costs causes it to stop merging states beforeit hits the failure. I spent some time trying to find a variant that wouldfail in 9.3, without success; but I'm sure such cases exist.)Like the previous patch, back-patch to 9.3 where this code was added.Report:https://postgr.es/m/E2B01A4B-4530-406B-8D17-2F67CF9A16BA@csuhta.com
1 parent139eb96 commit1dffabe

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3 files changed

+136
-42
lines changed

3 files changed

+136
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lines changed

‎contrib/pg_trgm/expected/pg_trgm.out

Lines changed: 17 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -3497,6 +3497,7 @@ create table test2(t text COLLATE "C");
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insert into test2 values ('abcdef');
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insert into test2 values ('quark');
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insert into test2 values (' z foo bar');
3500+
insert into test2 values ('/123/-45/');
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create index test2_idx_gin on test2 using gin (t gin_trgm_ops);
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set enable_seqscan=off;
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explain (costs off)
@@ -3598,7 +3599,8 @@ select * from test2 where t ~ '(abc)*$';
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abcdef
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quark
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z foo bar
3601-
(3 rows)
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/123/-45/
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(4 rows)
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select * from test2 where t ~* 'DEF';
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t
@@ -3690,6 +3692,12 @@ select * from test2 where t ~ 'qua(?!foo)';
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quark
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(1 row)
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3695+
select * from test2 where t ~ '/\d+/-\d';
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t
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-----------
3698+
/123/-45/
3699+
(1 row)
3700+
36933701
drop index test2_idx_gin;
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create index test2_idx_gist on test2 using gist (t gist_trgm_ops);
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set enable_seqscan=off;
@@ -3784,7 +3792,8 @@ select * from test2 where t ~ '(abc)*$';
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abcdef
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quark
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z foo bar
3787-
(3 rows)
3795+
/123/-45/
3796+
(4 rows)
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37893798
select * from test2 where t ~* 'DEF';
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t
@@ -3876,6 +3885,12 @@ select * from test2 where t ~ 'qua(?!foo)';
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quark
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(1 row)
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3888+
select * from test2 where t ~ '/\d+/-\d';
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t
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-----------
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/123/-45/
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(1 row)
3893+
38793894
-- Check similarity threshold (bug #14202)
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CREATE TEMP TABLE restaurants (city text);
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INSERT INTO restaurants SELECT 'Warsaw' FROM generate_series(1, 10000);

‎contrib/pg_trgm/sql/pg_trgm.sql

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -52,6 +52,7 @@ create table test2(t text COLLATE "C");
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insert into test2values ('abcdef');
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insert into test2values ('quark');
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insert into test2values (' z foo bar');
55+
insert into test2values ('/123/-45/');
5556
createindextest2_idx_ginon test2 using gin (t gin_trgm_ops);
5657
set enable_seqscan=off;
5758
explain (costs off)
@@ -87,6 +88,7 @@ select * from test2 where t ~ ' z foo bar';
8788
select*from test2where t ~' z foo bar';
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select*from test2where t ~' z foo';
8990
select*from test2where t ~'qua(?!foo)';
91+
select*from test2where t ~'/\d+/-\d';
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dropindex test2_idx_gin;
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9294
createindextest2_idx_giston test2 using gist (t gist_trgm_ops);
@@ -124,6 +126,7 @@ select * from test2 where t ~ ' z foo bar';
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select*from test2where t ~' z foo bar';
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select*from test2where t ~' z foo';
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select*from test2where t ~'qua(?!foo)';
129+
select*from test2where t ~'/\d+/-\d';
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128131
-- Check similarity threshold (bug #14202)
129132

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