[core] Enables buffer spill when targetFileSize is greater than the w…

docs/layouts/shortcodes/generated/core_configuration.html

@@ -1048,7 +1048,7 @@
             <td><h5>write-buffer-spillable</h5></td>
             <td style="word-wrap: break-word;">(none)</td>
             <td>Boolean</td>
-            <td>Whether the write buffer can be spillable. Enabled by default when using object storage.</td>
+            <td>Whether the write buffer can be spillable. Enabled by default when using object storage or when 'target-file-size' is greater than 'write-buffer-size'.</td>
         </tr>
         <tr>
             <td><h5>write-manifest-cache</h5></td>

paimon-common/src/main/java/org/apache/paimon/CoreOptions.java

@@ -479,7 +479,7 @@ public class CoreOptions implements Serializable {
                     .booleanType()
                     .noDefaultValue()
                     .withDescription(
-                            "Whether the write buffer can be spillable. Enabled by default when using object storage.");
+                            "Whether the write buffer can be spillable. Enabled by default when using object storage or when 'target-file-size' is greater than 'write-buffer-size'.");
 
     public static final ConfigOption<Boolean> WRITE_BUFFER_FOR_APPEND =
             key("write-buffer-for-append")
@@ -1957,9 +1957,14 @@ public long writeBufferSize() {
         return options.get(WRITE_BUFFER_SIZE).getBytes();
     }
 
-    public boolean writeBufferSpillable(boolean usingObjectStore, boolean isStreaming) {
+    public boolean writeBufferSpillable(
+            boolean usingObjectStore, boolean isStreaming, boolean hasPrimaryKey) {
         // if not streaming mode, we turn spillable on by default.
-        return options.getOptional(WRITE_BUFFER_SPILLABLE).orElse(usingObjectStore || !isStreaming);
+        return options.getOptional(WRITE_BUFFER_SPILLABLE)
+                .orElse(
+                        usingObjectStore
+                                || !isStreaming
+                                || targetFileSize(hasPrimaryKey) > writeBufferSize());
     }
 
     public MemorySize writeBufferSpillDiskSize() {

paimon-core/src/main/java/org/apache/paimon/operation/AppendOnlyFileStoreWrite.java

@@ -125,7 +125,7 @@ protected RecordWriter<InternalRow> createWriter(
                 pathFactory.createDataFilePathFactory(partition, bucket),
                 restoreIncrement,
                 options.useWriteBufferForAppend() || forceBufferSpill,
-                options.writeBufferSpillable(fileIO.isObjectStore(), isStreamingMode)
+                options.writeBufferSpillable(fileIO.isObjectStore(), isStreamingMode, false)
                         || forceBufferSpill,
                 options.fileCompression(),
                 options.spillCompressOptions(),

paimon-core/src/main/java/org/apache/paimon/operation/KeyValueFileStoreWrite.java

@@ -229,7 +229,7 @@ protected MergeTreeWriter createWriter(
 
     @VisibleForTesting
     public boolean bufferSpillable() {
-        return options.writeBufferSpillable(fileIO.isObjectStore(), isStreamingMode);
+        return options.writeBufferSpillable(fileIO.isObjectStore(), isStreamingMode, true);
     }
 
     private CompactManager createCompactManager(

paimon-core/src/test/java/org/apache/paimon/append/AppendOnlyWriterTest.java

@@ -409,6 +409,54 @@ public void testNoBuffer() throws Exception {
         writer.close();
     }
 
+    @Test
+    public void tesWriteBufferSpillAutoEnabled() {
+        HashMap<String, String> map = new HashMap<>();
+        // This is the default behavior,no object store and streaming mode.
+        Assertions.assertThat(CoreOptions.fromMap(map).writeBufferSpillable(false, true, false))
+                .isFalse();
+
+        // Using object store.
+        Assertions.assertThat(CoreOptions.fromMap(map).writeBufferSpillable(true, true, false))
+                .isTrue();
+
+        // Batch mode.
+        Assertions.assertThat(CoreOptions.fromMap(map).writeBufferSpillable(false, false, false))
+                .isTrue();
+
+        // Append only table.
+        map.put(CoreOptions.WRITE_BUFFER_SIZE.key(), "200 MB");
+        Assertions.assertThat(CoreOptions.fromMap(map).writeBufferSpillable(false, false, false))
+                .isTrue();
+
+        // Primary key table.
+        map.put(CoreOptions.WRITE_BUFFER_SIZE.key(), "100 MB");
+        Assertions.assertThat(CoreOptions.fromMap(map).writeBufferSpillable(false, false, true))
+                .isTrue();
+
+        // targetFileSize is greater than write buffer size.
+        map.clear();
+        map.put(CoreOptions.TARGET_FILE_SIZE.key(), "2 b");
+        map.put(CoreOptions.WRITE_BUFFER_SIZE.key(), "1 b");
+        Assertions.assertThat(CoreOptions.fromMap(map).writeBufferSpillable(false, true, false))
+                .isTrue();
+
+        // target-file-size is smaller than write-buffer-size.
+        map.clear();
+        map.put(CoreOptions.TARGET_FILE_SIZE.key(), "1 b");
+        map.put(CoreOptions.WRITE_BUFFER_SIZE.key(), "2 b");
+        Assertions.assertThat(CoreOptions.fromMap(map).writeBufferSpillable(false, true, false))
+                .isFalse();
+
+        // Set to false manually.
+        map.clear();
+        map.put(CoreOptions.TARGET_FILE_SIZE.key(), "2 b");
+        map.put(CoreOptions.WRITE_BUFFER_SIZE.key(), "1 b");
+        map.put(CoreOptions.WRITE_BUFFER_SPILLABLE.key(), "false");
+        Assertions.assertThat(CoreOptions.fromMap(map).writeBufferSpillable(false, true, false))
+                .isFalse();
+    }
+
     @Test
     public void testMultipleFlush() throws Exception {
         AppendOnlyWriter writer = createEmptyWriter(Long.MAX_VALUE, true);

paimon-flink/paimon-flink-common/src/test/java/org/apache/paimon/flink/sink/WriterOperatorTest.java

@@ -87,6 +87,7 @@ public void testPrimaryKeyTableMetrics() throws Exception {
         Options options = new Options();
         options.set("bucket", "1");
         options.set("write-buffer-size", "256 b");
+        options.set("write-buffer-spillable", "false");
         options.set("page-size", "32 b");
 
         FileStoreTable table =
@@ -332,6 +333,7 @@ public void testNumWritersMetric() throws Exception {
         Options options = new Options();
         options.set("bucket", "1");
         options.set("write-buffer-size", "256 b");
+        options.set("write-buffer-spillable", "false");
         options.set("page-size", "32 b");
 
         FileStoreTable fileStoreTable =