Fix contrib/pg_trgm's similarity() function for trigram-free strings.
authorTom Lane <tgl@sss.pgh.pa.us>
Wed, 13 Feb 2013 19:07:06 +0000 (14:07 -0500)
committerTom Lane <tgl@sss.pgh.pa.us>
Wed, 13 Feb 2013 19:07:06 +0000 (14:07 -0500)
commit9728eda7925b6d42621b38c48e91ef9ab8d90cbc
tree5f36156374357ff9251c15acdc838b35784c9ade
parentcd89965aab34463252b9354bc1bf1bcf0339c102
Fix contrib/pg_trgm's similarity() function for trigram-free strings.

Cases such as similarity('', '') produced a NaN result due to computing
0/0.  Per discussion, make it return zero instead.

This appears to be the basic cause of bug #7867 from Michele Baravalle,
although it remains unclear why her installation doesn't think Cyrillic
letters are letters.

Back-patch to all active branches.
contrib/pg_trgm/expected/pg_trgm.out
contrib/pg_trgm/sql/pg_trgm.sql
contrib/pg_trgm/trgm_op.c