Exclude zero vectors for cosine distance to be consistent with other types [skip ci]

sql/vector.sql

@@ -912,6 +912,7 @@ CREATE OPERATOR CLASS minivec_cosine_ops
 	FOR TYPE minivec USING ivfflat AS
 	OPERATOR 1 <=> (minivec, minivec) FOR ORDER BY float_ops,
 	FUNCTION 1 cosine_distance(minivec, minivec),
+	FUNCTION 2 l2_norm(minivec),
 	FUNCTION 3 minivec_spherical_distance(minivec, minivec),
 	FUNCTION 4 l2_norm(minivec),
 	FUNCTION 5 ivfflat_minivec_support(internal);

src/ivfutils.c

@@ -71,6 +71,9 @@ IvfflatOptionalProcInfo(Relation index, uint16 procnum)
 Datum
 IvfflatNormValue(const IvfflatTypeInfo * typeInfo, Oid collation, Datum value)
 {
+	if (!typeInfo->normalize)
+		return value;
+
 	return DirectFunctionCall1Coll(typeInfo->normalize, collation, value);
 }
 
@@ -392,7 +395,8 @@ ivfflat_minivec_support(PG_FUNCTION_ARGS)
 {
 	static const IvfflatTypeInfo typeInfo = {
 		.maxDimensions = IVFFLAT_MAX_DIM * 4,
-		.normalize = minivec_l2_normalize,
+		/* Do not normalize to maximize precision */
+		.normalize = NULL,
 		.itemSize = MinivecItemSize,
 		.updateCenter = MinivecUpdateCenter,
 		.sumCenter = MinivecSumCenter