Fix maxThreads option to be optional instead of required

# Conflicts:
#	data-loader/cli/src/test/java/com/scalar/db/dataloader/cli/command/dataimport/ImportCommandTest.java

Author: ypeckstadt

data-loader/cli/src/main/java/com/scalar/db/dataloader/cli/command/dataexport/ExportCommand.java

@@ -61,7 +61,11 @@ public Integer call() throws Exception {
       FileUtils.validateFilePath(scalarDbPropertiesFilePath);
       validatePositiveValue(
           spec.commandLine(), dataChunkSize, DataLoaderError.INVALID_DATA_CHUNK_SIZE);
-      validatePositiveValue(spec.commandLine(), maxThreads, DataLoaderError.INVALID_MAX_THREADS);
+      if (maxThreads != null) {
+        validatePositiveValue(spec.commandLine(), maxThreads, DataLoaderError.INVALID_MAX_THREADS);
+      } else {
+        maxThreads = Runtime.getRuntime().availableProcessors();
+      }
 
       StorageFactory storageFactory = StorageFactory.create(scalarDbPropertiesFilePath);
       TableMetadataService metaDataService =

data-loader/cli/src/main/java/com/scalar/db/dataloader/cli/command/dataexport/ExportCommandOptions.java

@@ -77,7 +77,7 @@ public class ExportCommandOptions {
       paramLabel = "<MAX_THREADS>",
       description =
           "Maximum number of threads to use for parallel processing (default: number of available processors)")
-  protected int maxThreads;
+  protected Integer maxThreads;
 
   @CommandLine.Option(
       names = {"--start-key", "-sk"},

data-loader/cli/src/main/java/com/scalar/db/dataloader/cli/command/dataimport/ImportCommand.java

@@ -61,7 +61,11 @@ public Integer call() throws Exception {
         spec.commandLine(), dataChunkSize, DataLoaderError.INVALID_DATA_CHUNK_SIZE);
     validatePositiveValue(
         spec.commandLine(), transactionSize, DataLoaderError.INVALID_TRANSACTION_SIZE);
-    validatePositiveValue(spec.commandLine(), maxThreads, DataLoaderError.INVALID_MAX_THREADS);
+    if (maxThreads != null) {
+      validatePositiveValue(spec.commandLine(), maxThreads, DataLoaderError.INVALID_MAX_THREADS);
+    } else {
+      maxThreads = Runtime.getRuntime().availableProcessors();
+    }
     validatePositiveValue(
         spec.commandLine(), dataChunkQueueSize, DataLoaderError.INVALID_DATA_CHUNK_QUEUE_SIZE);
     ControlFile controlFile = parseControlFileFromPath(controlFilePath).orElse(null);

data-loader/cli/src/main/java/com/scalar/db/dataloader/cli/command/dataimport/ImportCommandOptions.java

@@ -42,9 +42,8 @@ public class ImportCommandOptions {
       names = {"--max-threads", "-mt"},
       paramLabel = "<MAX_THREADS>",
       description =
-          "Maximum number of threads to use for parallel processing (default: number of available processors)",
-      defaultValue = "16")
-  protected int maxThreads;
+          "Maximum number of threads to use for parallel processing (default: number of available processors)")
+  protected Integer maxThreads;
 
   // Deprecated option - kept for backward compatibility
   @CommandLine.Option(

data-loader/cli/src/test/java/com/scalar/db/dataloader/cli/command/dataexport/ExportCommandTest.java

@@ -190,4 +190,58 @@ void call_withOnlyDeprecatedEndExclusive_shouldApplyInvertedValue() {
     // end-exclusive=false should become end-inclusive=true
     assertEquals(true, command.scanEndInclusive);
   }
+
+  @Test
+  void call_withMaxThreadsSpecified_shouldUseSpecifiedValue() {
+    // Simulate command line parsing with --max-threads
+    String[] args = {
+      "--config",
+      "scalardb.properties",
+      "--namespace",
+      "scalar",
+      "--table",
+      "asset",
+      "--format",
+      "JSON",
+      "--max-threads",
+      "8"
+    };
+    ExportCommand command = new ExportCommand();
+    CommandLine cmd = new CommandLine(command);
+    cmd.parseArgs(args);
+
+    // Verify the value was parsed
+    assertEquals(8, command.maxThreads);
+  }
+
+  @Test
+  void call_withoutMaxThreads_shouldDefaultToAvailableProcessors() {
+    // Simulate command line parsing without --max-threads
+    String[] args = {
+      "--config",
+      "scalardb.properties",
+      "--namespace",
+      "scalar",
+      "--table",
+      "asset",
+      "--format",
+      "JSON"
+    };
+    ExportCommand command = new ExportCommand();
+    CommandLine cmd = new CommandLine(command);
+    cmd.parseArgs(args);
+
+    // Verify maxThreads is null before validation
+    assertEquals(null, command.maxThreads);
+
+    // Simulate what happens in call() after validation
+    command.spec = cmd.getCommandSpec();
+    command.applyDeprecatedOptions();
+    if (command.maxThreads == null) {
+      command.maxThreads = Runtime.getRuntime().availableProcessors();
+    }
+
+    // Verify it was set to available processors
+    assertEquals(Runtime.getRuntime().availableProcessors(), command.maxThreads);
+  }
 }

data-loader/cli/src/test/java/com/scalar/db/dataloader/cli/command/dataimport/ImportCommandTest.java

@@ -229,4 +229,54 @@ void call_withEnableLogSuccessShortForm_shouldSetToTrueWithoutValue() throws Exc
     // Verify the short form flag was parsed correctly without requiring a value
     assertTrue(command.enableLogSuccessRecords);
   }
+
+  @Test
+  void call_withMaxThreadsSpecified_shouldUseSpecifiedValue() {
+    // Simulate command line parsing with --max-threads
+    String[] args = {
+      "--config",
+      "scalardb.properties",
+      "--file",
+      "import.json",
+      "--namespace",
+      "scalar",
+      "--table",
+      "asset",
+      "--max-threads",
+      "8"
+    };
+    ImportCommand command = new ImportCommand();
+    CommandLine cmd = new CommandLine(command);
+    cmd.parseArgs(args);
+
+    // Verify the value was parsed
+    assertEquals(8, command.maxThreads);
+  }
+
+  @Test
+  void call_withoutMaxThreads_shouldDefaultToAvailableProcessors() {
+    // Simulate command line parsing without --max-threads
+    String[] args = {
+      "--config", "scalardb.properties",
+      "--file", "import.json",
+      "--namespace", "scalar",
+      "--table", "asset"
+    };
+    ImportCommand command = new ImportCommand();
+    CommandLine cmd = new CommandLine(command);
+    cmd.parseArgs(args);
+
+    // Verify maxThreads is null before validation
+    assertEquals(null, command.maxThreads);
+
+    // Simulate what happens in call() after validation
+    command.spec = cmd.getCommandSpec();
+    command.applyDeprecatedOptions();
+    if (command.maxThreads == null) {
+      command.maxThreads = Runtime.getRuntime().availableProcessors();
+    }
+
+    // Verify it was set to available processors
+    assertEquals(Runtime.getRuntime().availableProcessors(), command.maxThreads);
+  }
 }

data-loader/core/src/main/java/com/scalar/db/dataloader/core/dataexport/ExportManager.java

@@ -77,11 +77,8 @@ public ExportReport startExport(
       handleTransactionMetadata(exportOptions, tableMetadata);
       processHeader(exportOptions, tableMetadata, writer);
 
-      int maxThreadCount =
-          exportOptions.getMaxThreadCount() == 0
-              ? Runtime.getRuntime().availableProcessors()
-              : exportOptions.getMaxThreadCount();
-      ExecutorService executorService = Executors.newFixedThreadPool(maxThreadCount);
+      ExecutorService executorService =
+          Executors.newFixedThreadPool(exportOptions.getMaxThreadCount());
 
       BufferedWriter bufferedWriter = new BufferedWriter(writer);
       boolean isJson = exportOptions.getOutputFileFormat() == FileFormat.JSON;

data-loader/core/src/main/java/com/scalar/db/dataloader/core/dataexport/ExportOptions.java

@@ -21,10 +21,10 @@ public class ExportOptions {
   private final FileFormat outputFileFormat;
   private final ScanRange scanRange;
   private final int limit;
-  private final int maxThreadCount;
   private final boolean prettyPrintJson;
 
   @Builder.Default private final int dataChunkSize = 200;
+  @Builder.Default private final int maxThreadCount = Runtime.getRuntime().availableProcessors();
   @Builder.Default private final String delimiter = ";";
   @Builder.Default private final boolean excludeHeaderRow = false;
   @Builder.Default private final boolean includeTransactionMetadata = false;

data-loader/core/src/main/java/com/scalar/db/dataloader/core/dataimport/ImportOptions.java

@@ -34,7 +34,7 @@ public class ImportOptions {
   private final ControlFile controlFile;
   private final String namespace;
   private final String tableName;
-  private final int maxThreads;
+  @Builder.Default private final int maxThreads = Runtime.getRuntime().availableProcessors();
   private final String customHeaderRow;
   private final int dataChunkQueueSize;
 }

data-loader/core/src/test/java/com/scalar/db/dataloader/core/dataexport/JsonExportManagerTest.java

@@ -130,4 +130,32 @@ void startExport_givenPartitionKey_shouldGenerateOutputFile()
     Assertions.assertTrue(file.exists());
     Assertions.assertTrue(file.delete());
   }
+
+  @Test
+  void exportOptions_withoutMaxThreadCount_shouldUseDefaultAvailableProcessors() {
+    // Create ExportOptions without explicitly setting maxThreadCount
+    ExportOptions exportOptions =
+        ExportOptions.builder("namespace", "table", null, FileFormat.JSON)
+            .sortOrders(Collections.emptyList())
+            .scanRange(new ScanRange(null, null, false, false))
+            .build();
+
+    // Verify the default was applied
+    Assertions.assertEquals(
+        Runtime.getRuntime().availableProcessors(), exportOptions.getMaxThreadCount());
+  }
+
+  @Test
+  void exportOptions_withExplicitMaxThreadCount_shouldUseProvidedValue() {
+    // Create ExportOptions with explicit maxThreadCount
+    ExportOptions exportOptions =
+        ExportOptions.builder("namespace", "table", null, FileFormat.JSON)
+            .sortOrders(Collections.emptyList())
+            .scanRange(new ScanRange(null, null, false, false))
+            .maxThreadCount(8)
+            .build();
+
+    // Verify the explicit value was used
+    Assertions.assertEquals(8, exportOptions.getMaxThreadCount());
+  }
 }