Hash opclass for spoint

Besides hash indexes on spoint, this enables "select distinct spoint
from tbl" queries.

Close #101.

Makefile

@@ -55,7 +55,7 @@ CRUSH_TESTS = init_extended circle_extended
 PGS_SQL     = pgs_types.sql pgs_point.sql pgs_euler.sql pgs_circle.sql \
               pgs_line.sql pgs_ellipse.sql pgs_polygon.sql pgs_path.sql \
               pgs_box.sql pgs_contains_ops.sql pgs_contains_ops_compat.sql \
-              pgs_gist.sql gnomo.sql pgs_brin.sql pgs_circle_sel.sql
+              pgs_gist.sql gnomo.sql pgs_brin.sql pgs_circle_sel.sql pgs_hash.sql
 
 ifneq ($(USE_HEALPIX),0)
 TESTS      += healpix moc moc1 moc100 mocautocast
@@ -199,7 +199,7 @@ ifeq ($(has_index_options),y)
 pg_sphere--1.3.1--1.3.2.sql: pgs_moc_options.sql.in
 endif
 endif
-pg_sphere--1.3.1--1.3.2.sql: pgs_circle_sel.sql.in
+pg_sphere--1.3.1--1.3.2.sql: pgs_circle_sel.sql.in pgs_hash.sql.in
 	cat upgrade_scripts/$@.in $^ > $@
 
 # end of local stuff

doc/indices.sgm

@@ -153,4 +153,29 @@
 
       </sect1>
 
+      <sect1 id="ind.hash">
+        <title>
+          Hash index
+        </title>
+        <para>
+          Values of type <type>spoint</type> can be indexed using a
+          <literal>HASH</literal> index, supporting the
+          <link linkend="op.equal"><literal>=</literal></link> operator.
+          The <literal>spoint_hash_ops</literal> operator class also enables
+          <literal>DISTINCT</literal> queries on <type>spoint</type>.
+        </para>
+        <example>
+          <title>Hash index of spoints</title>
+          <programlisting>
+<![CDATA[CREATE TABLE sky (]]>
+<![CDATA[  star spoint]]>
+<![CDATA[);]]>
+<![CDATA[CREATE INDEX ON sky USING HASH (star);]]>
+<![CDATA[]]>
+<![CDATA[SELECT DISTINCT star FROM sky;]]>
+          </programlisting>
+        </example>
+
+      </sect1>
+
 </chapter>

expected/index.out

@@ -195,3 +195,39 @@ EXPLAIN (COSTS OFF) SELECT count(*) FROM spheretmp1b WHERE p = spoint '(3.09 , 1
      4
 (1 row)
 
+-- test hash opclass
+CREATE TABLE spheretmp1c AS TABLE spheretmp1;
+SELECT p FROM spheretmp1c WHERE p <@ scircle '<(1,1),0.2>' ORDER BY p::text;
+       p       
+---------------
+ (0.67 , 0.97)
+ (0.67 , 0.97)
+ (0.67 , 0.97)
+ (0.67 , 0.97)
+ (1.07 , 1.09)
+ (1.07 , 1.09)
+ (1.07 , 1.09)
+ (1.07 , 1.09)
+ (1.24 , 0.95)
+ (1.24 , 0.95)
+ (1.24 , 0.95)
+ (1.24 , 0.95)
+(12 rows)
+
+WITH points AS (SELECT DISTINCT p FROM spheretmp1c WHERE p <@ scircle '<(1,1),0.2>')
+   SELECT p FROM points ORDER BY p::text;
+       p       
+---------------
+ (0.67 , 0.97)
+ (1.07 , 1.09)
+ (1.24 , 0.95)
+(3 rows)
+
+CREATE INDEX spheretmp1c_hash_idx ON spheretmp1c USING hash(p);
+EXPLAIN (COSTS OFF) SELECT * FROM spheretmp1c WHERE p = '(0.67 , 0.97)';
+                      QUERY PLAN                      
+------------------------------------------------------
+ Index Scan using spheretmp1c_hash_idx on spheretmp1c
+   Index Cond: (p = '(0.67 , 0.97)'::spoint)
+(2 rows)
+

pgs_hash.sql.in

@@ -0,0 +1,19 @@
+CREATE FUNCTION spoint_hash32 (spoint)
+   RETURNS int
+   IMMUTABLE STRICT
+   PARALLEL SAFE
+   LANGUAGE C
+   AS 'MODULE_PATHNAME', 'spherepoint_hash32';
+
+UPDATE pg_operator
+   SET oprcanhash = true
+   WHERE oprname = '=' AND
+     oprleft = 'spoint'::regtype AND oprright = 'spoint'::regtype;
+
+/* PG17: ALTER OPERATOR = (spoint, spoint) SET (HASHES); */
+
+CREATE OPERATOR CLASS spoint_hash_ops
+   DEFAULT FOR TYPE spoint USING hash
+   AS
+      OPERATOR 1 = (spoint, spoint),
+      FUNCTION 1 spoint_hash32(spoint);

sql/index.sql

@@ -76,3 +76,14 @@ EXPLAIN (COSTS OFF) SELECT count(*) FROM spheretmp1b WHERE p <@ scircle '<(1,1),
                     SELECT count(*) FROM spheretmp1b WHERE p <@ scircle '<(1,1),0.3>';
 EXPLAIN (COSTS OFF) SELECT count(*) FROM spheretmp1b WHERE p = spoint '(3.09 , 1.25)';
                     SELECT count(*) FROM spheretmp1b WHERE p = spoint '(3.09 , 1.25)';
+
+-- test hash opclass
+
+CREATE TABLE spheretmp1c AS TABLE spheretmp1;
+
+SELECT p FROM spheretmp1c WHERE p <@ scircle '<(1,1),0.2>' ORDER BY p::text;
+WITH points AS (SELECT DISTINCT p FROM spheretmp1c WHERE p <@ scircle '<(1,1),0.2>')
+   SELECT p FROM points ORDER BY p::text;
+
+CREATE INDEX spheretmp1c_hash_idx ON spheretmp1c USING hash(p);
+EXPLAIN (COSTS OFF) SELECT * FROM spheretmp1c WHERE p = '(0.67 , 0.97)';

src/point.c

@@ -16,6 +16,7 @@ PG_FUNCTION_INFO_V1(spherepoint_y);
 PG_FUNCTION_INFO_V1(spherepoint_z);
 PG_FUNCTION_INFO_V1(spherepoint_xyz);
 PG_FUNCTION_INFO_V1(spherepoint_equal);
+PG_FUNCTION_INFO_V1(spherepoint_hash32);
 
 static Oid point_id = InvalidOid;
 
@@ -309,3 +310,13 @@ spherepoint_equal(PG_FUNCTION_ARGS)
 
 	PG_RETURN_BOOL(spoint_eq(p1, p2));
 }
+
+Datum
+spherepoint_hash32(PG_FUNCTION_ARGS)
+{
+	SPoint	   *p1 = (SPoint *) PG_GETARG_POINTER(0);
+	Datum		h1 = DirectFunctionCall1(hashfloat8, p1->lat);
+	Datum		h2 = DirectFunctionCall1(hashfloat8, p1->lng);
+
+	PG_RETURN_INT32(DatumGetInt32(h1) ^ DatumGetInt32(h2));
+}

src/point.h

@@ -102,4 +102,9 @@ Datum	spherepoint_xyz(PG_FUNCTION_ARGS);
  */
 Datum	spherepoint_equal(PG_FUNCTION_ARGS);
 
+/*
+ * Compute a 32-bit hash value of a point.
+ */
+Datum	spherepoint_hash32(PG_FUNCTION_ARGS);
+
 #endif