fix(oracle): speed up schema diff and add comment sync (closes #198)

- Replace ALL_OBJECTS with ALL_TABLES UNION ALL_VIEWS in list_databases
  query to avoid slow full scan on large Oracle instances
- Add loading indicator in SchemaDiffDialog during database/schema loading
- Generate COMMENT ON TABLE/COLUMN statements in schema diff sync SQL
- Compare column and table comments in diff detection

crates/dbx-core/src/db/oracle_driver.rs

@@ -62,9 +62,9 @@ pub async fn list_databases(conn: &OracleClient) -> Result<Vec<DatabaseInfo>, St
             "WITH schema_names AS ( \
                SELECT SYS_CONTEXT('USERENV', 'CURRENT_SCHEMA') AS owner FROM DUAL \
                UNION \
-               SELECT DISTINCT owner \
-               FROM all_objects \
-               WHERE object_type IN ('TABLE', 'VIEW') \
+               SELECT DISTINCT owner FROM all_tables \
+               UNION \
+               SELECT DISTINCT owner FROM all_views \
              ) \
              SELECT owner \
              FROM schema_names \

src/components/diff/SchemaDiffDialog.vue

@@ -48,6 +48,7 @@ const targetSchemas = ref<string[]>([]);
 const step = ref<"select" | "comparing" | "result">("select");
 const diffs = ref<TableDiff[]>([]);
 const syncSql = ref("");
+const loadingMeta = ref(false);
 const executing = ref(false);
 
 const sqlConnections = computed(() =>
@@ -71,6 +72,7 @@ function connectionIconType(connectionId: string) {
 
 async function loadDatabases(connectionId: string, side: "source" | "target") {
   if (!connectionId) return;
+  loadingMeta.value = true;
   try {
     await store.ensureConnected(connectionId);
     const dbs = await api.listDatabases(connectionId);
@@ -89,6 +91,8 @@ async function loadDatabases(connectionId: string, side: "source" | "target") {
   } catch {
     if (side === "source") sourceDatabases.value = [];
     else targetDatabases.value = [];
+  } finally {
+    loadingMeta.value = false;
   }
 }
 
@@ -141,6 +145,8 @@ async function startCompare() {
 
     const srcTableNames = srcTables.filter((t) => t.table_type !== "VIEW").map((t) => t.name);
     const tgtTableNames = tgtTables.filter((t) => t.table_type !== "VIEW").map((t) => t.name);
+    const srcTableComments = new Map(srcTables.map((t) => [t.name, t.comment ?? null]));
+    const tgtTableComments = new Map(tgtTables.map((t) => [t.name, t.comment ?? null]));
     const srcViewNames = srcTables.filter((t) => t.table_type === "VIEW").map((t) => t.name);
     const tgtViewNames = tgtTables.filter((t) => t.table_type === "VIEW").map((t) => t.name);
     const { added, removed, common } = diffTables(srcTableNames, tgtTableNames);
@@ -181,8 +187,17 @@ async function startCompare() {
       const idxDiffs = diffIndexes(srcIdx, tgtIdx);
       const fkDiffs = diffForeignKeys(srcFks, tgtFks);
       const triggerDiffs = diffTriggers(srcTriggers, tgtTriggers);
+      const srcComment = srcTableComments.get(name) ?? null;
+      const tgtComment = tgtTableComments.get(name) ?? null;
+      const commentChanged = (srcComment ?? "") !== (tgtComment ?? "");
 
-      if (colDiffs.length > 0 || idxDiffs.length > 0 || fkDiffs.length > 0 || triggerDiffs.length > 0) {
+      if (
+        colDiffs.length > 0 ||
+        idxDiffs.length > 0 ||
+        fkDiffs.length > 0 ||
+        triggerDiffs.length > 0 ||
+        commentChanged
+      ) {
         result.push({
           type: "modified",
           objectType: "table",
@@ -191,6 +206,8 @@ async function startCompare() {
           indexes: idxDiffs.length > 0 ? idxDiffs : undefined,
           foreignKeys: fkDiffs.length > 0 ? fkDiffs : undefined,
           triggers: triggerDiffs.length > 0 ? triggerDiffs : undefined,
+          sourceTableComment: commentChanged ? srcComment : undefined,
+          targetTableComment: commentChanged ? tgtComment : undefined,
         });
       }
     }
@@ -403,9 +420,10 @@ watch(open, async (val) => {
           </div>
         </div>
 
-        <Button v-if="step === 'select'" size="sm" :disabled="!canCompare" @click="startCompare">
-          <GitCompareArrows class="w-3.5 h-3.5 mr-1" />
-          {{ t("diff.compare") }}
+        <Button v-if="step === 'select'" size="sm" :disabled="!canCompare || loadingMeta" @click="startCompare">
+          <Loader2 v-if="loadingMeta" class="w-3.5 h-3.5 mr-1 animate-spin" />
+          <GitCompareArrows v-else class="w-3.5 h-3.5 mr-1" />
+          {{ loadingMeta ? t("common.loading") : t("diff.compare") }}
         </Button>
 
         <!-- Comparing -->

src/lib/schemaDiff.ts

@@ -41,6 +41,8 @@ export interface TableDiff {
   foreignKeys?: ForeignKeyDiff[];
   triggers?: TriggerDiff[];
   ddl?: string;
+  sourceTableComment?: string | null;
+  targetTableComment?: string | null;
 }
 
 export function diffColumns(source: ColumnInfo[], target: ColumnInfo[]): ColumnDiff[] {
@@ -63,6 +65,9 @@ export function diffColumns(source: ColumnInfo[], target: ColumnInfo[]): ColumnD
       if ((sc.column_default ?? "") !== (tc.column_default ?? "")) {
         changes.push(`default: ${tc.column_default ?? "NULL"} → ${sc.column_default ?? "NULL"}`);
       }
+      if ((sc.comment ?? "") !== (tc.comment ?? "")) {
+        changes.push(`comment: ${tc.comment ?? ""} → ${sc.comment ?? ""}`);
+      }
       if (changes.length > 0) {
         diffs.push({ type: "modified", name: sc.name, source: sc, target: tc, changes });
       }
@@ -268,6 +273,34 @@ function dropObjectSql(diff: TableDiff, dbType: DatabaseType, schema?: string):
   return `DROP ${objectType} IF EXISTS ${qualifiedName(diff.name, dbType, schema)};`;
 }
 
+function commentLiteral(comment: string): string {
+  return `'${comment.replace(/'/g, "''")}'`;
+}
+
+function columnCommentSql(
+  tableName: string,
+  colName: string,
+  comment: string,
+  dbType: DatabaseType,
+  schema?: string,
+): string {
+  const isMySQL = dbType === "mysql" || dbType === "doris" || dbType === "starrocks";
+  if (isMySQL) {
+    return `-- Column comment for ${colName}: use ALTER TABLE ... MODIFY COLUMN to set comment in MySQL`;
+  }
+  const qt = qualifiedName(tableName, dbType, schema);
+  return `COMMENT ON COLUMN ${qt}.${quoteId(colName, dbType)} IS ${commentLiteral(comment)};`;
+}
+
+function tableCommentSql(tableName: string, comment: string, dbType: DatabaseType, schema?: string): string {
+  const isMySQL = dbType === "mysql" || dbType === "doris" || dbType === "starrocks";
+  const qt = qualifiedName(tableName, dbType, schema);
+  if (isMySQL) {
+    return `ALTER TABLE ${qt} COMMENT = ${commentLiteral(comment)};`;
+  }
+  return `COMMENT ON TABLE ${qt} IS ${commentLiteral(comment)};`;
+}
+
 export function generateSyncSql(diffs: TableDiff[], dbType: DatabaseType, schema?: string): string {
   const lines: string[] = [];
   const isMySQL = dbType === "mysql" || dbType === "doris" || dbType === "starrocks";
@@ -351,6 +384,21 @@ export function generateSyncSql(diffs: TableDiff[], dbType: DatabaseType, schema
         lines.push("");
       }
 
+      if (diff.columns) {
+        for (const col of diff.columns) {
+          if (col.source && col.changes?.some((c) => c.startsWith("comment:"))) {
+            lines.push(columnCommentSql(diff.name, col.name, col.source.comment ?? "", dbType, schema));
+          }
+          if (col.type === "added" && col.source?.comment) {
+            lines.push(columnCommentSql(diff.name, col.name, col.source.comment, dbType, schema));
+          }
+        }
+      }
+
+      if (diff.sourceTableComment !== undefined && diff.sourceTableComment !== diff.targetTableComment) {
+        lines.push(tableCommentSql(diff.name, diff.sourceTableComment ?? "", dbType, schema));
+      }
+
       if (diff.indexes) {
         for (const idx of diff.indexes) {
           if (idx.type === "added" && idx.source) {