Support ifNotExists in add column

core/src/main/java/com/scalar/db/api/Admin.java

@@ -3,6 +3,7 @@
 import com.scalar.db.common.CoreError;
 import com.scalar.db.exception.storage.ExecutionException;
 import com.scalar.db.io.DataType;
+import com.scalar.db.util.ScalarDbUtils;
 import java.util.Collections;
 import java.util.Map;
 import java.util.Set;
@@ -441,6 +442,43 @@ default void addNewColumnToTable(
     }
   }
 
+  /**
+   * Adds a new column to an existing table. The new column cannot be a partition or clustering key.
+   * <br>
+   * See {@link #addNewColumnToTable(String, String, String, DataType)} for more information.
+   *
+   * @param namespace the table namespace
+   * @param table the table name
+   * @param columnName the name of the new column
+   * @param columnType the type of the new column
+   * @param encrypted whether the new column should be encrypted
+   * @param ifNotExists if set to true, the column will be added only if it does not exist already.
+   *     If set to false, it will throw an exception if it already exists
+   * @throws IllegalArgumentException if the table does not exist
+   * @throws ExecutionException if the operation fails
+   */
+  default void addNewColumnToTable(
+      String namespace,
+      String table,
+      String columnName,
+      DataType columnType,
+      boolean encrypted,
+      boolean ifNotExists)
+      throws ExecutionException {
+    if (encrypted) {
+      throw new UnsupportedOperationException(CoreError.ENCRYPTION_NOT_ENABLED.buildMessage());
+    }
+    TableMetadata tableMetadata = getTableMetadata(namespace, table);
+    if (tableMetadata == null) {
+      throw new IllegalArgumentException(
+          CoreError.TABLE_NOT_FOUND.buildMessage(ScalarDbUtils.getFullTableName(namespace, table)));
+    }
+    if (ifNotExists && tableMetadata.getColumnNames().contains(columnName)) {
+      return;
+    }
+    addNewColumnToTable(namespace, table, columnName, columnType);
+  }
+
   /**
    * Imports an existing table that is not managed by ScalarDB.
    *

core/src/main/java/com/scalar/db/common/DecoratedDistributedTransactionAdmin.java

@@ -195,6 +195,19 @@ public void addNewColumnToTable(
         namespace, table, columnName, columnType, encrypted);
   }
 
+  @Override
+  public void addNewColumnToTable(
+      String namespace,
+      String table,
+      String columnName,
+      DataType columnType,
+      boolean encrypted,
+      boolean ifNotExists)
+      throws ExecutionException {
+    distributedTransactionAdmin.addNewColumnToTable(
+        namespace, table, columnName, columnType, encrypted, ifNotExists);
+  }
+
   @Override
   public void importTable(String namespace, String table, Map<String, String> options)
       throws ExecutionException {

integration-test/src/main/java/com/scalar/db/api/DistributedStorageAdminIntegrationTestBase.java

@@ -1010,6 +1010,19 @@ public void addNewColumnToTable_ForAlreadyExistingColumn_ShouldThrowIllegalArgum
         .isInstanceOf(IllegalArgumentException.class);
   }
 
+  @Test
+  public void
+      addNewColumnToTable_IfNotExists_ForAlreadyExistingColumn_ShouldNotThrowAnyException() {
+    // Arrange
+
+    // Act Assert
+    assertThatCode(
+            () ->
+                admin.addNewColumnToTable(
+                    namespace1, getTable1(), getColumnName7(), DataType.TEXT, false, true))
+        .doesNotThrowAnyException();
+  }
+
   @Test
   public void
       upgrade_WhenMetadataTableExistsButNotNamespacesTable_ShouldCreateNamespacesTableAndImportExistingNamespaces()

integration-test/src/main/java/com/scalar/db/api/DistributedTransactionAdminIntegrationTestBase.java

@@ -886,6 +886,19 @@ public void addNewColumnToTable_ForAlreadyExistingColumn_ShouldThrowIllegalArgum
         .isInstanceOf(IllegalArgumentException.class);
   }
 
+  @Test
+  public void
+      addNewColumnToTable_IfNotExists_ForAlreadyExistingColumn_ShouldNotThrowAnyException() {
+    // Arrange
+
+    // Act Assert
+    assertThatCode(
+            () ->
+                admin.addNewColumnToTable(
+                    namespace1, TABLE1, COL_NAME7, DataType.TEXT, false, true))
+        .doesNotThrowAnyException();
+  }
+
   @Test
   public void createCoordinatorTables_ShouldCreateCoordinatorTablesCorrectly()
       throws ExecutionException {