Fix hamming_dist calculation

src/hnsw.c

@@ -291,10 +291,26 @@ static float4 array_dist(ArrayType *a, ArrayType *b, usearch_metric_kind_t metri
         elog(ERROR, "expected equally sized arrays but got arrays with dimensions %d and %d", a_dim, b_dim);
     }
 
-    float4 *ax = (float4 *)ARR_DATA_PTR(a);
-    float4 *bx = (float4 *)ARR_DATA_PTR(b);
+    float4 result;
+    bool   is_int_array = (metric_kind == usearch_metric_hamming_k);
 
-    return usearch_dist(ax, bx, metric_kind, a_dim, usearch_scalar_f32_k);
+    if(is_int_array) {
+        int32 *ax_int = (int32 *)ARR_DATA_PTR(a);
+        int32 *bx_int = (int32 *)ARR_DATA_PTR(b);
+
+        // calling usearch_scalar_f32_k here even though it's an integer array is fine
+        // the hamming distance in usearch actually ignores the scalar type
+        // and it will get casted appropriately in usearch even with this scalar type
+        result = usearch_dist(ax_int, bx_int, metric_kind, a_dim, usearch_scalar_f32_k);
+
+    } else {
+        float4 *ax = (float4 *)ARR_DATA_PTR(a);
+        float4 *bx = (float4 *)ARR_DATA_PTR(b);
+
+        result = usearch_dist(ax, bx, metric_kind, a_dim, usearch_scalar_f32_k);
+    }
+
+    return result;
 }
 
 static float8 vector_dist(Vector *a, Vector *b, usearch_metric_kind_t metric_kind)
@@ -330,7 +346,7 @@ Datum       hamming_dist(PG_FUNCTION_ARGS)
 {
     ArrayType *a = PG_GETARG_ARRAYTYPE_P(0);
     ArrayType *b = PG_GETARG_ARRAYTYPE_P(1);
-    PG_RETURN_INT32(array_dist(a, b, usearch_metric_hamming_k));
+    PG_RETURN_INT32((int32)array_dist(a, b, usearch_metric_hamming_k));
 }
 
 PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_l2sq_dist);
@@ -371,36 +387,32 @@ HnswColumnType GetIndexColumnType(Relation index)
 }
 
 /*
- * Given vector data and vector type, convert it to a float4 array
+ * Given vector data and vector type, read it as either a float4 or int32 array and return as void*
  */
-float4 *DatumGetSizedFloatArray(Datum datum, HnswColumnType type, int dimensions)
+void *DatumGetSizedArray(Datum datum, HnswColumnType type, int dimensions)
 {
     if(type == VECTOR) {
         Vector *vector = DatumGetVector(datum);
         if(vector->dim != dimensions) {
             elog(ERROR, "Expected vector with dimension %d, got %d", dimensions, vector->dim);
         }
-        return vector->x;
+        return (void *)vector->x;
     } else if(type == REAL_ARRAY) {
         ArrayType *array = DatumGetArrayTypePCopy(datum);
         int        array_dim = ArrayGetNItems(ARR_NDIM(array), ARR_DIMS(array));
         if(array_dim != dimensions) {
             elog(ERROR, "Expected real array with dimension %d, got %d", dimensions, array_dim);
         }
-        return (float4 *)ARR_DATA_PTR(array);
+        return (void *)((float4 *)ARR_DATA_PTR(array));
     } else if(type == INT_ARRAY) {
         ArrayType *array = DatumGetArrayTypePCopy(datum);
         int        array_dim = ArrayGetNItems(ARR_NDIM(array), ARR_DIMS(array));
         if(array_dim != dimensions) {
             elog(ERROR, "Expected int array with dimension %d, got %d", dimensions, array_dim);
         }
-        int    *intArray = (int *)ARR_DATA_PTR(array);
-        float4 *floatArray = (float4 *)palloc(sizeof(float) * array_dim);
-        for(int i = 0; i < array_dim; i++) {
-            floatArray[ i ] = (float)intArray[ i ];
-        }
-        // todo:: free this array
-        return floatArray;
+
+        int32 *intArray = (int32 *)ARR_DATA_PTR(array);
+        return (void *)intArray;
     } else {
         elog(ERROR, "Unsupported type");
     }

src/hnsw.h

@@ -34,7 +34,7 @@ PGDLLEXPORT Datum cos_dist(PG_FUNCTION_ARGS);
 
 HnswColumnType GetColumnTypeFromOid(Oid oid);
 HnswColumnType GetIndexColumnType(Relation index);
-float4        *DatumGetSizedFloatArray(Datum datum, HnswColumnType type, int dimensions);
+void          *DatumGetSizedArray(Datum datum, HnswColumnType type, int dimensions);
 
 #define LDB_UNUSED(x) (void)(x)
 

src/hnsw/build.c

@@ -65,16 +65,17 @@ static void AddTupleToUsearchIndex(ItemPointer tid, Datum *values, HnswBuildStat
     usearch_error_t       error = NULL;
     Datum                 value = PointerGetDatum(PG_DETOAST_DATUM(values[ 0 ]));
     usearch_scalar_kind_t usearch_scalar;
-    float4               *vector = DatumGetSizedFloatArray(value, buildstate->columnType, buildstate->dimensions);
 
+    void *vector = DatumGetSizedArray(value, buildstate->columnType, buildstate->dimensions);
     switch(buildstate->columnType) {
         case REAL_ARRAY:
         case VECTOR:
             usearch_scalar = usearch_scalar_f32_k;
             break;
         case INT_ARRAY:
-            // q:: I think in this case we need to do a type conversion from int to float
-            // before passing the buffer to usearch
+            // this is fine, since we only use integer arrays with hamming distance metric
+            // and hamming distance in usearch doesn't care about scalar type
+            // also, usearch will appropriately cast integer arrays even with this scalar type
             usearch_scalar = usearch_scalar_f32_k;
             break;
         default:

src/hnsw/insert.c

@@ -132,7 +132,7 @@ bool ldb_aminsert(Relation         index,
     assert(!error);
 
     datum = PointerGetDatum(PG_DETOAST_DATUM(values[ 0 ]));
-    float4 *vector = DatumGetSizedFloatArray(datum, insertstate->columnType, opts.dimensions);
+    void *vector = DatumGetSizedArray(datum, insertstate->columnType, opts.dimensions);
 
 #if LANTERNDB_COPYNODES
     // currently not fully ported to the latest changes

src/hnsw/scan.c

@@ -162,7 +162,7 @@ bool ldb_amgettuple(IndexScanDesc scan, ScanDirection dir)
     if(scanstate->first) {
         int             num_returned;
         Datum           value;
-        float4         *vec;
+        void           *vec;
         usearch_error_t error = NULL;
         int             k = ldb_hnsw_init_k;
 
@@ -183,7 +183,7 @@ bool ldb_amgettuple(IndexScanDesc scan, ScanDirection dir)
         Assert(!VARATT_IS_COMPRESSED(DatumGetPointer(value)));
         Assert(!VARATT_IS_EXTENDED(DatumGetPointer(value)));
 
-        vec = DatumGetSizedFloatArray(value, scanstate->columnType, scanstate->dimensions);
+        vec = DatumGetSizedArray(value, scanstate->columnType, scanstate->dimensions);
 
         if(scanstate->distances == NULL) {
             scanstate->distances = palloc(k * sizeof(float));
@@ -209,7 +209,7 @@ bool ldb_amgettuple(IndexScanDesc scan, ScanDirection dir)
     if(scanstate->current == scanstate->count) {
         int             num_returned;
         Datum           value;
-        float4         *vec;
+        void           *vec;
         usearch_error_t error = NULL;
         int             k = scanstate->count * 2;
         int             index_size = usearch_size(scanstate->usearch_index, &error);
@@ -221,7 +221,7 @@ bool ldb_amgettuple(IndexScanDesc scan, ScanDirection dir)
 
         value = scan->orderByData->sk_argument;
 
-        vec = DatumGetSizedFloatArray(value, scanstate->columnType, scanstate->dimensions);
+        vec = DatumGetSizedArray(value, scanstate->columnType, scanstate->dimensions);
 
         /* double k and reallocate arrays to account for increased size */
         scanstate->distances = repalloc(scanstate->distances, k * sizeof(float));

test/expected/hnsw_dist_func.out

@@ -33,7 +33,7 @@ INFO:  inserted 0 elements
 INFO:  done saving 0 vectors
 INSERT INTO small_world_l2 SELECT id, v FROM small_world;
 INSERT INTO small_world_cos SELECT id, v FROM small_world;
-INSERT INTO small_world_ham SELECT id, v FROM small_world;
+INSERT INTO small_world_ham SELECT id, ARRAY[CAST(v[1] AS INTEGER), CAST(v[2] AS INTEGER), CAST(v[3] AS INTEGER)] FROM small_world;
 SET enable_seqscan = false;
 -- Verify that the distance functions work (check distances)
 SELECT ROUND(l2sq_dist(v, '{0,1,0}')::numeric, 2) FROM small_world_l2 ORDER BY v <-> '{0,1,0}';
@@ -220,3 +220,22 @@ WITH t AS (SELECT id FROM test1 ORDER BY v <-> '{1,2}' LIMIT 1) SELECT id, COUNT
 ERROR:  Operator <-> can only be used inside of an index
 WITH t AS (SELECT id FROM test1 ORDER BY v <-> '{1,2}') SELECT id FROM t UNION SELECT id FROM t;
 ERROR:  Operator <-> can only be used inside of an index
+-- Check that hamming distance query results are sorted correctly
+CREATE TABLE extra_small_world_ham (
+    id SERIAL PRIMARY KEY,
+    v INT[2]
+);
+INSERT INTO extra_small_world_ham (v) VALUES ('{0,0}'), ('{1,1}'), ('{2,2}'), ('{3,3}');
+CREATE INDEX ON extra_small_world_ham USING hnsw (v dist_hamming_ops) WITH (dim=2);
+INFO:  done init usearch index
+INFO:  inserted 4 elements
+INFO:  done saving 4 vectors
+SELECT ROUND(hamming_dist(v, '{0,0}')::numeric, 2) FROM extra_small_world_ham ORDER BY v <-> '{0,0}';
+ round 
+-------
+  0.00
+  2.00
+  2.00
+  4.00
+(4 rows)
+

test/expected/hnsw_todo.out

@@ -29,25 +29,6 @@ SELECT id, ROUND(l2sq_dist(vector_int, array[0,1,0])::numeric, 2) as dist
 FROM small_world_l2
 ORDER BY vector_int <-> array[0,1,0] LIMIT 7;
 ERROR:  Operator <-> can only be used inside of an index
--- this result is not sorted correctly
-CREATE TABLE small_world_ham (
-    id SERIAL PRIMARY KEY,
-    v INT[2]
-);
-INSERT INTO small_world_ham (v) VALUES ('{0,0}'), ('{1,1}'), ('{2,2}'), ('{3,3}');
-CREATE INDEX ON small_world_ham USING hnsw (v dist_hamming_ops) WITH (dim=2);
-INFO:  done init usearch index
-INFO:  inserted 4 elements
-INFO:  done saving 4 vectors
-SELECT ROUND(hamming_dist(v, '{0,0}')::numeric, 2) FROM small_world_ham ORDER BY v <-> '{0,0}';
- round 
--------
-  0.00
-  2.00
-  4.00
-  2.00
-(4 rows)
-
 --- Test scenarious ---
 -----------------------------------------
 -- Case:

test/sql/hnsw_dist_func.sql

@@ -14,7 +14,7 @@ CREATE INDEX ON small_world_ham USING hnsw (v dist_hamming_ops) WITH (dim=3);
 
 INSERT INTO small_world_l2 SELECT id, v FROM small_world;
 INSERT INTO small_world_cos SELECT id, v FROM small_world;
-INSERT INTO small_world_ham SELECT id, v FROM small_world;
+INSERT INTO small_world_ham SELECT id, ARRAY[CAST(v[1] AS INTEGER), CAST(v[2] AS INTEGER), CAST(v[3] AS INTEGER)] FROM small_world;
 
 SET enable_seqscan = false;
 
@@ -88,4 +88,13 @@ SELECT 1 FROM test1 ORDER BY v <-> (SELECT '{1,3}'::real[]);
 SELECT t2_results.id FROM test1 t1 JOIN LATERAL (SELECT t2.id FROM test2 t2 ORDER BY t1.v <-> t2.v LIMIT 1) t2_results ON TRUE;
 WITH t AS (SELECT id FROM test1 ORDER BY v <-> '{1,2}' LIMIT 1) SELECT DISTINCT id FROM t;
 WITH t AS (SELECT id FROM test1 ORDER BY v <-> '{1,2}' LIMIT 1) SELECT id, COUNT(*) FROM t GROUP BY 1;
-WITH t AS (SELECT id FROM test1 ORDER BY v <-> '{1,2}') SELECT id FROM t UNION SELECT id FROM t;
+WITH t AS (SELECT id FROM test1 ORDER BY v <-> '{1,2}') SELECT id FROM t UNION SELECT id FROM t;
+
+-- Check that hamming distance query results are sorted correctly
+CREATE TABLE extra_small_world_ham (
+    id SERIAL PRIMARY KEY,
+    v INT[2]
+);
+INSERT INTO extra_small_world_ham (v) VALUES ('{0,0}'), ('{1,1}'), ('{2,2}'), ('{3,3}');
+CREATE INDEX ON extra_small_world_ham USING hnsw (v dist_hamming_ops) WITH (dim=2);
+SELECT ROUND(hamming_dist(v, '{0,0}')::numeric, 2) FROM extra_small_world_ham ORDER BY v <-> '{0,0}';

test/sql/hnsw_todo.sql

@@ -32,15 +32,6 @@ SELECT id, ROUND(l2sq_dist(vector_int, array[0,1,0])::numeric, 2) as dist
 FROM small_world_l2
 ORDER BY vector_int <-> array[0,1,0] LIMIT 7;
 
--- this result is not sorted correctly
-CREATE TABLE small_world_ham (
-    id SERIAL PRIMARY KEY,
-    v INT[2]
-);
-INSERT INTO small_world_ham (v) VALUES ('{0,0}'), ('{1,1}'), ('{2,2}'), ('{3,3}');
-CREATE INDEX ON small_world_ham USING hnsw (v dist_hamming_ops) WITH (dim=2);
-SELECT ROUND(hamming_dist(v, '{0,0}')::numeric, 2) FROM small_world_ham ORDER BY v <-> '{0,0}';
-
 --- Test scenarious ---
 -----------------------------------------
 -- Case: