DB Schema Migration: Ignore duplicate column errors

src/database/schemamanager.cpp

@@ -189,6 +189,24 @@ SchemaManager::Result SchemaManager::upgradeToSchemaVersion(
             }
             FwdSqlQuery query(m_database, statement);
             result = query.isPrepared() && query.execPrepared();
+            if (!result &&
+                    query.hasError() &&
+                    query.lastError().databaseText().startsWith(
+                            QStringLiteral("duplicate column name: "))) {
+                // New columns may have already been added during a previous
+                // migration to a different (= preceding) schema version. This
+                // is a very common situation during development when switching
+                // between schema versions. Since SQLite does not allow to add
+                // new columns only if they do not yet exist we need to account
+                // for and handle those errors here after they occurred. If the
+                // remaining migration finishes without other errors this is
+                // probably ok.
+                kLogger.warning()
+                        << "Ignoring failed statement"
+                        << statement
+                        << "and continuing with schema migration";
+                result = true;
+            }
         }
 
         if (result) {

src/test/schemamanager_test.cpp

@@ -104,7 +104,28 @@ TEST_F(SchemaManagerTest, BackwardsIncompatibleVersion) {
     EXPECT_EQ(SchemaManager::Result::NewerVersionIncompatible, result);
 }
 
-TEST_F(SchemaManagerTest, FailedUpgrade) {
+TEST_F(SchemaManagerTest, IgnoreDuplicateColumn) {
+    // Establish preconditions for test
+    {
+        // Upgrade to version 3 to get the modern library table.
+        SchemaManager schemaManager(dbConnection());
+        SchemaManager::Result result = schemaManager.upgradeToSchemaVersion(
+                MixxxDb::kDefaultSchemaFile, 3);
+        ASSERT_EQ(SchemaManager::Result::UpgradeSucceeded, result);
+    }
+
+    // Add a column that will be added again in version 24.
+    QSqlQuery query(dbConnection());
+    ASSERT_TRUE(query.exec(
+            "ALTER TABLE library ADD COLUMN coverart_source TEXT"));
+
+    SchemaManager schemaManager(dbConnection());
+    SchemaManager::Result result = schemaManager.upgradeToSchemaVersion(
+            MixxxDb::kDefaultSchemaFile, MixxxDb::kRequiredSchemaVersion);
+    EXPECT_EQ(SchemaManager::Result::UpgradeSucceeded, result);
+}
+
+TEST_F(SchemaManagerTest, UpgradeFailed) {
     // Establish preconditions for test
     {
         // Upgrade to version 3 to get the modern library table.
@@ -114,10 +135,10 @@ TEST_F(SchemaManagerTest, FailedUpgrade) {
         EXPECT_EQ(SchemaManager::Result::UpgradeSucceeded, result);
     }
 
-    // Add a column that is added in version 24.
+    // Drop a table that is expected to exist.
     QSqlQuery query(dbConnection());
     EXPECT_TRUE(query.exec(
-            "ALTER TABLE library ADD COLUMN coverart_source TEXT"));
+            "DROP TABLE PlaylistTracks"));
 
     SchemaManager schemaManager(dbConnection());
     SchemaManager::Result result = schemaManager.upgradeToSchemaVersion(

src/util/db/fwdsqlquery.h

@@ -1,5 +1,4 @@
-#ifndef MIXXX_FWDSQLQUERY_H
-#define MIXXX_FWDSQLQUERY_H
+#pragma once
 
 
 #include <QSqlQuery>
@@ -45,7 +44,11 @@ class FwdSqlQuery: protected QSqlQuery {
     }
 
     bool hasError() const {
-        return lastError().isValid() && (lastError().type() != QSqlError::NoError);
+        return lastError().isValid() &&
+                (lastError().type() != QSqlError::NoError);
+    }
+    QSqlError lastError() const {
+        return QSqlQuery::lastError();
     }
 
     static const int BOOLEAN_FALSE = 0;
@@ -112,6 +115,3 @@ class FwdSqlQuery: protected QSqlQuery {
 
     bool m_prepared;
 };
-
-
-#endif // MIXXX_FWDSQLQUERY_H