fix: ensure nullable binary arrays return boxed type arrays instead of Object[] in BinaryStreamReader

Author: kishansinghifs1

CHANGELOG.md

@@ -4,6 +4,8 @@
 
 ### Bug Fixes 
 
+- **[client-v2]** Fixed binary array decoding for nullable element types so `Array(Nullable(Float64))` and similar columns now return boxed arrays such as `Double[]` instead of `Object[]`. This keeps null-supporting arrays aligned with their element type while preserving the existing `Object[]` fallback for Variant/Dynamic/Geometry arrays. (https://github.com/ClickHouse/clickhouse-java/issues/2846)
+
 - **[client-v2]** Fixed container query parameters being sent unquoted, so `Client.query(sql, params, settings)` binding
   a `List<LocalDate>` (or an array/`Map`) to a placeholder like `{ids:Array(Date)}` was rejected by the server with
   `CANNOT_PARSE_INPUT_ASSERTION_FAILED`. Parameter values are now formatted by

client-v2/src/main/java/com/clickhouse/client/api/data_formats/internal/BinaryStreamReader.java

@@ -625,8 +625,13 @@ public ArrayValue readArray(ClickHouseColumn column) throws IOException {
 
     public ArrayValue readArrayItem(ClickHouseColumn itemTypeColumn, int len) throws IOException {
         ArrayValue array;
-        if (itemTypeColumn.isNullable()
-                || itemTypeColumn.getDataType() == ClickHouseDataType.Variant
+        if (itemTypeColumn.isNullable()) {
+            Class<?> itemClass = itemTypeColumn.getDataType().getObjectClass();
+            array = new ArrayValue(itemClass == null ? Object.class : itemClass, len);
+            for (int i = 0; i < len; i++) {
+                array.set(i, readValue(itemTypeColumn));
+            }
+        } else if (itemTypeColumn.getDataType() == ClickHouseDataType.Variant
                 || itemTypeColumn.getDataType() == ClickHouseDataType.Dynamic
                 || itemTypeColumn.getDataType() == ClickHouseDataType.Geometry) {
             array = new ArrayValue(Object.class, len);

client-v2/src/test/java/com/clickhouse/client/api/data_formats/internal/BinaryStreamReaderTests.java

@@ -1,6 +1,7 @@
 package com.clickhouse.client.api.data_formats.internal;
 
 import com.clickhouse.data.ClickHouseColumn;
+import com.clickhouse.data.format.BinaryStreamUtils;
 
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
@@ -204,4 +205,27 @@ public void testReadNullVariantReturnsNull() throws Exception {
 
         Assert.assertNull(reader.readValue(column));
     }
+
+    @Test
+    public void testNullableArrayValueUsesBoxedComponentType() throws Exception {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        BinaryStreamUtils.writeVarInt(baos, 2);
+        BinaryStreamUtils.writeNonNull(baos);
+        BinaryStreamUtils.writeFloat64(baos, 1.0);
+        BinaryStreamUtils.writeNonNull(baos);
+        BinaryStreamUtils.writeFloat64(baos, 2.0);
+
+        BinaryStreamReader reader = new BinaryStreamReader(
+                new ByteArrayInputStream(baos.toByteArray()),
+                TimeZone.getTimeZone("UTC"),
+                null,
+                new BinaryStreamReader.CachingByteBufferAllocator(),
+                false,
+                null);
+
+        BinaryStreamReader.ArrayValue array = (BinaryStreamReader.ArrayValue) reader.readValue(
+                ClickHouseColumn.of("v", "Array(Nullable(Float64))"));
+
+        Assert.assertEquals(array.getArray().getClass().getComponentType(), Double.class);
+    }
 }