Add IT for repairCoordinatorTables Coordinator schema upgrade

Verifies that calling repairCoordinatorTables with scalar.db.consensus_commit.coordinator.group_commit.enabled toggled from false to true against an existing pre-group-commit Coordinator table issues ALTER TABLE ADD COLUMN to add the child_ids column.

Author: brfrn169

core/src/main/java/com/scalar/db/transaction/consensuscommit/ConsensusCommitAdmin.java

@@ -350,8 +350,16 @@ public void repairCoordinatorTables(Map<String, String> options) throws Executio
       coordinatorTableMetadata = getCoordinatorTableMetadata();
     }
 
-    admin.repairTable(coordinatorNamespace, Coordinator.TABLE, coordinatorTableMetadata, options);
+    // Upgrade the schema (ALTER TABLE ADD COLUMN for any non-key columns the desired schema
+    // requires that the existing Coordinator is missing) BEFORE repairTable. addNewColumnToTable
+    // checks the existing metadata via getTableMetadata, so it must run while the metadata still
+    // reflects the pre-upgrade column set. If repairTable runs first, it upserts the metadata to
+    // the desired schema (which already includes the column), and the subsequent
+    // addNewColumnToTable call would be rejected with "column already exists" against the
+    // ScalarDB-side metadata even though the physical column does not yet exist.
     upgradeCoordinatorTableSchema(currentMetadata, coordinatorTableMetadata);
+
+    admin.repairTable(coordinatorNamespace, Coordinator.TABLE, coordinatorTableMetadata, options);
   }
 
   // Adds any non-key columns the desired Coordinator table schema requires that the existing

integration-test/src/main/java/com/scalar/db/transaction/consensuscommit/ConsensusCommitAdminRepairTableIntegrationTestBase.java

@@ -1,7 +1,16 @@
 package com.scalar.db.transaction.consensuscommit;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.scalar.db.api.DistributedStorageAdmin;
+import com.scalar.db.api.DistributedTransactionAdmin;
 import com.scalar.db.api.DistributedTransactionAdminRepairTableIntegrationTestBase;
+import com.scalar.db.api.TableMetadata;
+import com.scalar.db.config.DatabaseConfig;
+import com.scalar.db.service.StorageFactory;
+import com.scalar.db.service.TransactionFactory;
 import java.util.Properties;
+import org.junit.jupiter.api.Test;
 
 public abstract class ConsensusCommitAdminRepairTableIntegrationTestBase
     extends DistributedTransactionAdminRepairTableIntegrationTestBase {
@@ -18,4 +27,52 @@ protected final Properties getProperties(String testName) {
   }
 
   protected abstract Properties getProps(String testName);
+
+  @Test
+  public void
+      repairCoordinatorTables_WithExistingCoordinatorMissingChildIdsColumn_ShouldAddChildIdsColumn()
+          throws Exception {
+    // Arrange: drop the Coordinator created in setUp and recreate it via a separate admin
+    // instance that has group commit explicitly disabled, so the Coordinator table has no
+    // CHILD_IDS column.
+    admin.dropCoordinatorTables();
+
+    Properties propertiesWithGroupCommitDisabled = new Properties();
+    propertiesWithGroupCommitDisabled.putAll(getProperties(TEST_NAME));
+    propertiesWithGroupCommitDisabled.setProperty(
+        ConsensusCommitConfig.COORDINATOR_GROUP_COMMIT_ENABLED, "false");
+    try (DistributedTransactionAdmin adminWithGroupCommitDisabled =
+        TransactionFactory.create(propertiesWithGroupCommitDisabled).getTransactionAdmin()) {
+      waitForDifferentSessionDdl();
+      adminWithGroupCommitDisabled.createCoordinatorTables(getCreationOptions());
+    }
+
+    // Act: repair with group commit enabled. The existing Coordinator has no CHILD_IDS column,
+    // so this should add the column via ALTER TABLE ADD COLUMN.
+    Properties propertiesWithGroupCommitEnabled = new Properties();
+    propertiesWithGroupCommitEnabled.putAll(getProperties(TEST_NAME));
+    propertiesWithGroupCommitEnabled.setProperty(
+        ConsensusCommitConfig.COORDINATOR_GROUP_COMMIT_ENABLED, "true");
+    try (DistributedTransactionAdmin adminWithGroupCommitEnabled =
+        TransactionFactory.create(propertiesWithGroupCommitEnabled).getTransactionAdmin()) {
+      waitForDifferentSessionDdl();
+      adminWithGroupCommitEnabled.repairCoordinatorTables(getCreationOptions());
+
+      // Assert: the column now exists in the post-repair Coordinator metadata. We have to read the
+      // metadata via DistributedStorageAdmin (not via the transaction admin) because
+      // ConsensusCommitAdmin#getTableMetadata returns null for the coordinator namespace by design.
+      waitForDifferentSessionDdl();
+      String coordinatorNamespace =
+          new ConsensusCommitConfig(new DatabaseConfig(propertiesWithGroupCommitEnabled))
+              .getCoordinatorNamespace()
+              .orElse(Coordinator.NAMESPACE);
+      try (DistributedStorageAdmin storageAdmin =
+          StorageFactory.create(propertiesWithGroupCommitEnabled).getStorageAdmin()) {
+        TableMetadata metadata =
+            storageAdmin.getTableMetadata(coordinatorNamespace, Coordinator.TABLE);
+        assertThat(metadata).isNotNull();
+        assertThat(metadata.getColumnNames()).contains(Attribute.CHILD_IDS);
+      }
+    }
+  }
 }