Move CSV NULL value to constant

Author: ypeckstadt

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

@@ -16,4 +16,12 @@ public class Constants {
    */
   public static final String ABORT_TRANSACTION_STATUS =
       "Transaction aborted as part of batch transaction aborted";
+  /**
+   * Special null value representation used for TEXT data type columns in CSV files.
+   *
+   * <p>This value is used to distinguish between an empty string and a null value in CSV exports
+   * and imports. When exporting, null TEXT values are converted to this string. When importing,
+   * this string is converted back to null for TEXT columns.
+   */
+  public static final String CSV_TEXT_NULL_VALUE = "\\N";
 }

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

@@ -2,6 +2,7 @@
 
 import com.scalar.db.api.Result;
 import com.scalar.db.api.TableMetadata;
+import com.scalar.db.dataloader.core.Constants;
 import com.scalar.db.dataloader.core.DataLoaderError;
 import com.scalar.db.dataloader.core.util.CsvUtil;
 import com.scalar.db.dataloader.core.util.DecimalUtil;
@@ -118,10 +119,10 @@ private String convertResultToCsv(Result result) {
    */
   private String convertToString(Result result, String columnName, DataType dataType) {
     if (result.isNull(columnName)) {
-      // "\N" is added when a column of text data type has null value. This is only converted for
-      // CSV files
+      // Special null value is added when a column of text data type has null value. This is only
+      // converted for CSV files
       if (dataType.equals(DataType.TEXT)) {
-        return "\\N";
+        return Constants.CSV_TEXT_NULL_VALUE;
       }
       return null;
     }

data-loader/core/src/main/java/com/scalar/db/dataloader/core/util/ColumnUtils.java

@@ -4,6 +4,7 @@
 import com.scalar.db.api.Result;
 import com.scalar.db.api.TableMetadata;
 import com.scalar.db.dataloader.core.ColumnInfo;
+import com.scalar.db.dataloader.core.Constants;
 import com.scalar.db.dataloader.core.DataLoaderError;
 import com.scalar.db.dataloader.core.exception.Base64Exception;
 import com.scalar.db.dataloader.core.exception.ColumnParsingException;
@@ -85,7 +86,7 @@ public static Column<?> createColumnFromValue(
     String columnName = columnInfo.getColumnName();
     if (value != null) {
       if (dataType.equals(DataType.TEXT)) {
-        if ("\\N".equals(value)) {
+        if (Constants.CSV_TEXT_NULL_VALUE.equals(value)) {
           value = null;
         }
       } else if (value.equalsIgnoreCase("null")) {

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

@@ -3,6 +3,7 @@
 import com.scalar.db.api.Result;
 import com.scalar.db.api.TableMetadata;
 import com.scalar.db.common.ResultImpl;
+import com.scalar.db.dataloader.core.Constants;
 import com.scalar.db.dataloader.core.UnitTestUtils;
 import com.scalar.db.io.Column;
 import com.scalar.db.io.DataType;
@@ -122,7 +123,9 @@ void process_withValidResultList_withPartialProjectionsAndMetadata_shouldReturnV
   void
       process_withValidResultListWithTextFieldWithNullValue_shouldReturnValidCsvStringWithCustomNullValueForTextField() {
     String expectedOutput =
-        "9007199254740992,2147483647,true,0.000000000000000000000000000000000000000000001401298464324817,0.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000049,\\N,YmxvYiB0ZXN0IHZhbHVl,2000-01-01,01:01:01,2000-01-01T01:01,1970-01-21T03:20:41.740Z,0.000000000000000000000000000000000000000000001401298464324817,0.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000049,test value,YmxvYiB0ZXN0IHZhbHVl,txt value 464654654,2147483647,2147483647,9007199254740992,9007199254740992,test value,2147483647,2147483647,9007199254740992,9007199254740992";
+        "9007199254740992,2147483647,true,0.000000000000000000000000000000000000000000001401298464324817,0.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000049,"
+            + Constants.CSV_TEXT_NULL_VALUE
+            + ",YmxvYiB0ZXN0IHZhbHVl,2000-01-01,01:01:01,2000-01-01T01:01,1970-01-21T03:20:41.740Z,0.000000000000000000000000000000000000000000001401298464324817,0.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000049,test value,YmxvYiB0ZXN0IHZhbHVl,txt value 464654654,2147483647,2147483647,9007199254740992,9007199254740992,test value,2147483647,2147483647,9007199254740992,9007199254740992";
     Map<String, Column<?>> values = UnitTestUtils.createTestValues();
     String textColName = "col6";
     Column<?> col = values.get(textColName);

data-loader/core/src/test/java/com/scalar/db/dataloader/core/util/ColumnUtilsTest.java

@@ -8,6 +8,7 @@
 import com.scalar.db.api.TableMetadata;
 import com.scalar.db.common.ResultImpl;
 import com.scalar.db.dataloader.core.ColumnInfo;
+import com.scalar.db.dataloader.core.Constants;
 import com.scalar.db.dataloader.core.DataLoaderError;
 import com.scalar.db.dataloader.core.UnitTestUtils;
 import com.scalar.db.dataloader.core.exception.Base64Exception;
@@ -311,7 +312,7 @@ void createColumnFromValue_valueIsNullString_shouldRemainLiteralForTextType()
   }
 
   /**
-   * Tests that when the string value has custom null value "/N" is provided for TEXT columns, it is
+   * Tests that when the string value has custom null value is provided for TEXT columns, it is
    * treated as an actual null value
    */
   @Test
@@ -320,7 +321,8 @@ void createColumnFromValue_customNullValueForText_shouldBeConvertedToNull()
     String columnName = "textColumn";
     ColumnInfo columnInfo = ColumnInfo.builder().columnName(columnName).build();
 
-    Column<?> textCol = ColumnUtils.createColumnFromValue(DataType.TEXT, columnInfo, "\\N");
+    Column<?> textCol =
+        ColumnUtils.createColumnFromValue(DataType.TEXT, columnInfo, Constants.CSV_TEXT_NULL_VALUE);
     assertEquals(TextColumn.ofNull(columnName), textCol);
   }
 }