Added conversion for null text columns for import and export

Author: inv-jishnu

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

@@ -118,6 +118,9 @@ private String convertResultToCsv(Result result) {
    */
   private String convertToString(Result result, String columnName, DataType dataType) {
     if (result.isNull(columnName)) {
+      if (dataType.equals(DataType.TEXT)) {
+        return "/N";
+      }
       return null;
     }
     String value = "";

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

@@ -83,7 +83,8 @@ public static Column<?> createColumnFromValue(
       DataType dataType, ColumnInfo columnInfo, @Nullable String value)
       throws ColumnParsingException {
     String columnName = columnInfo.getColumnName();
-    if (value != null && !dataType.equals(DataType.TEXT) && value.equalsIgnoreCase("null")) {
+    if (value != null && (!dataType.equals(DataType.TEXT) && value.equalsIgnoreCase("null"))
+        || (dataType.equals(DataType.TEXT) && "/N".equals(value))) {
       value = null;
     }
     try {

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

@@ -6,6 +6,7 @@
 import com.scalar.db.dataloader.core.UnitTestUtils;
 import com.scalar.db.io.Column;
 import com.scalar.db.io.DataType;
+import com.scalar.db.io.TextColumn;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -116,4 +117,22 @@ void process_withValidResultList_withPartialProjectionsAndMetadata_shouldReturnV
     String output = csvProducerTask.process(resultList);
     Assertions.assertEquals(expectedOutput, output.trim());
   }
+
+  @Test
+  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";
+    Map<String, Column<?>> values = UnitTestUtils.createTestValues();
+    String textColName = "col6";
+    Column<?> col = values.get(textColName);
+    if (col instanceof TextColumn) {
+      values.put(textColName, TextColumn.of(textColName, null));
+    }
+    Result result = new ResultImpl(values, mockMetadata);
+    List<Result> resultList = new ArrayList<>();
+    resultList.add(result);
+    String output = csvProducerTask.process(resultList);
+    Assertions.assertEquals(expectedOutput, output.trim());
+  }
 }

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

@@ -309,4 +309,18 @@ void createColumnFromValue_valueIsNullString_shouldRemainLiteralForTextType()
     textCol = ColumnUtils.createColumnFromValue(DataType.TEXT, columnInfo, "nuLL");
     assertEquals(TextColumn.of(columnName, "nuLL"), textCol);
   }
+
+  /**
+   * Tests that when the string value custom null value "/n" is provided for TEXT columns, it is
+   * treated as an actual null value
+   */
+  @Test
+  void createColumnFromValue_valueIsCustomNullValue_shouldRemainLiteralForTextType()
+      throws ColumnParsingException {
+    String columnName = "textColumn";
+    ColumnInfo columnInfo = ColumnInfo.builder().columnName(columnName).build();
+
+    Column<?> textCol = ColumnUtils.createColumnFromValue(DataType.TEXT, columnInfo, "/N");
+    assertEquals(TextColumn.ofNull(columnName), textCol);
+  }
 }