Add bool GiST opclass to btree_gist

Adds bool opclass to btree_gist extension, to allow creating GiST
indexes on bool columns. GiST indexes on a single bool column don't seem
particularly useful, but this allows defining exclusion constraings
involving a bool column, for example.

Author: Emre Hasegeli
Reviewed-by: Andrey Borodin
Discussion: https://postgr.es/m/CAE2gYzyDKJBZngssR84VGZEN=Ux=V9FV23QfPgo+7-yYnKKg4g@mail.gmail.com

1 files changed, 96 insertions, 0 deletions

diff --git a/contrib/btree_gist/expected/bool.out b/contrib/btree_gist/expected/bool.out
new file mode 100644
index 00000000000..c67a9685d52
--- /dev/null
+++ b/contrib/btree_gist/expected/bool.out
@@ -0,0 +1,96 @@
+-- bool check
+CREATE TABLE booltmp (a bool);
+INSERT INTO booltmp VALUES (false), (true);
+SET enable_seqscan=on;
+SELECT count(*) FROM booltmp WHERE a <  true;
+ count 
+-------
+     1
+(1 row)
+
+SELECT count(*) FROM booltmp WHERE a <= true;
+ count 
+-------
+     2
+(1 row)
+
+SELECT count(*) FROM booltmp WHERE a  = true;
+ count 
+-------
+     1
+(1 row)
+
+SELECT count(*) FROM booltmp WHERE a >= true;
+ count 
+-------
+     1
+(1 row)
+
+SELECT count(*) FROM booltmp WHERE a >  true;
+ count 
+-------
+     0
+(1 row)
+
+CREATE INDEX boolidx ON booltmp USING gist ( a );
+SET enable_seqscan=off;
+SELECT count(*) FROM booltmp WHERE a <  true;
+ count 
+-------
+     1
+(1 row)
+
+SELECT count(*) FROM booltmp WHERE a <= true;
+ count 
+-------
+     2
+(1 row)
+
+SELECT count(*) FROM booltmp WHERE a  = true;
+ count 
+-------
+     1
+(1 row)
+
+SELECT count(*) FROM booltmp WHERE a >= true;
+ count 
+-------
+     1
+(1 row)
+
+SELECT count(*) FROM booltmp WHERE a >  true;
+ count 
+-------
+     0
+(1 row)
+
+-- Test index-only scans
+SET enable_bitmapscan=off;
+EXPLAIN (COSTS OFF)
+SELECT * FROM booltmp WHERE a;
+                QUERY PLAN                
+------------------------------------------
+ Index Only Scan using boolidx on booltmp
+   Filter: a
+(2 rows)
+
+SELECT * FROM booltmp WHERE a;
+ a 
+---
+ t
+(1 row)
+
+EXPLAIN (COSTS OFF)
+SELECT * FROM booltmp WHERE NOT a;
+                QUERY PLAN                
+------------------------------------------
+ Index Only Scan using boolidx on booltmp
+   Filter: (NOT a)
+(2 rows)
+
+SELECT * FROM booltmp WHERE NOT a;
+ a 
+---
+ f
+(1 row)
+