Fix bogus tree-flattening logic in QTNTernary().

QTNTernary() contains logic to flatten, eg, '(a & b) & c' into 'a & b & c',
which is all well and good, but it tries to do that to NOT nodes as well,
so that '!!a' gets changed to '!a'.  Explicitly restrict the conversion to
be done only on AND and OR nodes, and add a test case illustrating the bug.

In passing, provide some comments for the sadly naked functions in
tsquery_util.c, and simplify some baroque logic in QTNFree(), which
I think may have been leaking some items it intended to free.

Noted while investigating a complaint from Andreas Seltenreich.
Back-patch to all supported versions.

2 files changed, 9 insertions, 0 deletions

diff --git a/src/test/regress/expected/tsearch.out b/src/test/regress/expected/tsearch.out
index 9341dbe0d77..1466582c3ea 100644
--- a/src/test/regress/expected/tsearch.out
+++ b/src/test/regress/expected/tsearch.out
@@ -851,6 +851,13 @@ SELECT ts_rewrite('foo & bar & qq & new & york',  'new & york'::tsquery, 'big &
  'foo' & 'bar' & 'qq' & ( 'city' & 'new' & 'york' | ( 'nyc' | 'big' & 'apple' ) )
 (1 row)
 
+SELECT ts_rewrite(ts_rewrite('new & !york ', 'york', '!jersey'),
+                  'jersey', 'mexico');
+       ts_rewrite       
+------------------------
+ 'new' & !( !'mexico' )
+(1 row)
+
 SELECT ts_rewrite('moscow', 'SELECT keyword, sample FROM test_tsquery'::text );
      ts_rewrite      
 ---------------------
diff --git a/src/test/regress/sql/tsearch.sql b/src/test/regress/sql/tsearch.sql
index 9fd12076ace..6035d5e4272 100644
--- a/src/test/regress/sql/tsearch.sql
+++ b/src/test/regress/sql/tsearch.sql
@@ -305,6 +305,8 @@ SELECT COUNT(*) FROM test_tsquery WHERE keyword >  'new & york';
 RESET enable_seqscan;
 
 SELECT ts_rewrite('foo & bar & qq & new & york',  'new & york'::tsquery, 'big & apple | nyc | new & york & city');
+SELECT ts_rewrite(ts_rewrite('new & !york ', 'york', '!jersey'),
+                  'jersey', 'mexico');
 
 SELECT ts_rewrite('moscow', 'SELECT keyword, sample FROM test_tsquery'::text );
 SELECT ts_rewrite('moscow & hotel', 'SELECT keyword, sample FROM test_tsquery'::text );