pgsql: Support LIKE and ILIKE index searches via contrib/pg_trgm indexe

Support LIKE and ILIKE index searches via contrib/pg_trgm indexes.

Unlike Btree-based LIKE optimization, this works for non-left-anchored
search patterns. The effectiveness of the search depends on how many
trigrams can be extracted from the pattern. (The worst case, with no
trigrams, degrades to a full-table scan, so this isn't a panacea. But
it can be very useful.)

Alexander Korotkov, reviewed by Jan Urbanski

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=6e2f3ae8842392c46ccc91a9ce4bba92296890cb

Modified Files
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contrib/pg_trgm/expected/pg_trgm.out | 90 ++++++++++
contrib/pg_trgm/pg_trgm.sql.in | 16 ++-
contrib/pg_trgm/sql/pg_trgm.sql | 25 +++
contrib/pg_trgm/trgm.h | 22 ++-
contrib/pg_trgm/trgm_gin.c | 132 ++++++++++++++--
contrib/pg_trgm/trgm_gist.c | 95 ++++++++++--
contrib/pg_trgm/trgm_op.c | 286 +++++++++++++++++++++++++++++++--
contrib/pg_trgm/uninstall_pg_trgm.sql | 6 +-
doc/src/sgml/pgtrgm.sgml | 18 ++-
9 files changed, 640 insertions(+), 50 deletions(-)