commit d83bdef5428279be0126d20c7f75187b9f4847b0
Author: Joel Jakobsson <joel@compiler.org>
Date:   Fri Jun 16 17:14:49 2023 +0200

    Implement || operator to append an int to an int4hashset
    
    To avoid need for another C-function, the new SQL helper function
    int4_add_int4hashset() swaps the arguments of the || so that
    hashset_add() can be used for both scenarios.
    
    Also setseed() in the benchmark.sql for reproducibility.

diff --git a/hashset--0.0.1.sql b/hashset--0.0.1.sql
index 20d019d..2c2f9e8 100644
--- a/hashset--0.0.1.sql
+++ b/hashset--0.0.1.sql
@@ -82,6 +82,12 @@ RETURNS bigint
 AS 'hashset', 'int4hashset_collisions'
 LANGUAGE C IMMUTABLE;
 
+CREATE OR REPLACE FUNCTION int4_add_int4hashset(int4, int4hashset)
+RETURNS int4hashset
+AS $$SELECT $2 || $1$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE STRICT COST 1;
+
 /*
  * Aggregation Functions
  */
@@ -165,6 +171,20 @@ CREATE OPERATOR <> (
     HASHES
 );
 
+CREATE OPERATOR || (
+    leftarg = int4hashset,
+    rightarg = int4,
+    function = hashset_add,
+    commutator = ||
+);
+
+CREATE OPERATOR || (
+    leftarg = int4,
+    rightarg = int4hashset,
+    function = int4_add_int4hashset,
+    commutator = ||
+);
+
 /*
  * Hashset Hash Operators
  */
diff --git a/test/expected/basic.out b/test/expected/basic.out
index 65be2a6..5690ba4 100644
--- a/test/expected/basic.out
+++ b/test/expected/basic.out
@@ -220,6 +220,18 @@ SELECT '{1,2,3}'::int4hashset <> '{1,2,3,4}'::int4hashset; -- true
  t
 (1 row)
 
+SELECT '{1,2,3}'::int4hashset || 4;
+ ?column?  
+-----------
+ {1,3,2,4}
+(1 row)
+
+SELECT 4 || '{1,2,3}'::int4hashset;
+ ?column?  
+-----------
+ {1,3,2,4}
+(1 row)
+
 /*
  * Hashset Hash Operators
  */
diff --git a/test/sql/basic.sql b/test/sql/basic.sql
index 4882895..464884e 100644
--- a/test/sql/basic.sql
+++ b/test/sql/basic.sql
@@ -66,6 +66,9 @@ SELECT '{1,2,3}'::int4hashset <> '{4,5,6}'::int4hashset; -- true
 SELECT '{1,2,3}'::int4hashset <> '{1,2}'::int4hashset; -- true
 SELECT '{1,2,3}'::int4hashset <> '{1,2,3,4}'::int4hashset; -- true
 
+SELECT '{1,2,3}'::int4hashset || 4;
+SELECT 4 || '{1,2,3}'::int4hashset;
+
 /*
  * Hashset Hash Operators
  */
diff --git a/test/sql/benchmark.sql b/test/sql/benchmark.sql
index 6f825dc..1697451 100644
--- a/test/sql/benchmark.sql
+++ b/test/sql/benchmark.sql
@@ -58,6 +58,7 @@ $$ LANGUAGE plpgsql;
 
 \echo *** Testing 100000 random ints
 
+SELECT setseed(0.12345);
 \echo - Testing default hash function (Jenkins/lookup3)
 
 DO
@@ -75,6 +76,7 @@ BEGIN
 END
 $$ LANGUAGE plpgsql;
 
+SELECT setseed(0.12345);
 \echo - Testing Murmurhash32
 
 DO
@@ -92,6 +94,7 @@ BEGIN
 END
 $$ LANGUAGE plpgsql;
 
+SELECT setseed(0.12345);
 \echo - Testing naive hash function
 
 DO