fix: skip pagination wrapping for DDL and function calls

DDL statements (CREATE, ALTER, DROP, etc.) and function calls (CALL)
were being incorrectly wrapped with pagination SQL, causing syntax errors.
Now only SELECT, WITH, TABLE, and VALUES statements are paginated.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: prmoore77

src/backend/src/routes/api.ts

@@ -79,6 +79,28 @@ apiRouter.post('/disconnect', async (req: Request, res: Response) => {
   }
 });
 
+// Check if SQL statement can be paginated (only SELECT-like queries)
+function canPaginate(sql: string): boolean {
+  // Normalize: trim whitespace and remove leading comments
+  let normalized = sql.trim();
+
+  // Remove block comments /* ... */
+  normalized = normalized.replace(/\/\*[\s\S]*?\*\//g, '');
+  // Remove line comments -- ...
+  normalized = normalized.replace(/--[^\n]*/g, '');
+  // Trim again after removing comments
+  normalized = normalized.trim();
+
+  // Get the first keyword (case-insensitive)
+  const firstWord = normalized.split(/\s+/)[0]?.toUpperCase() || '';
+
+  // Only SELECT, WITH (CTE), TABLE, and VALUES can be paginated
+  // Note: EXPLAIN could return rows but wrapping it would change semantics
+  const paginatableKeywords = ['SELECT', 'WITH', 'TABLE', 'VALUES'];
+
+  return paginatableKeywords.includes(firstWord);
+}
+
 // Execute SQL query with optional pagination
 apiRouter.post('/query', async (req: Request, res: Response) => {
   try {
@@ -100,26 +122,35 @@ apiRouter.post('/query', async (req: Request, res: Response) => {
       return;
     }
 
-    // Apply pagination by wrapping the query
-    const pageLimit = typeof limit === 'number' ? limit : 1000; // Default page size
-    const pageOffset = typeof offset === 'number' ? offset : 0;
+    // Only apply pagination to SELECT-like queries
+    if (canPaginate(sql)) {
+      const pageLimit = typeof limit === 'number' ? limit : 1000; // Default page size
+      const pageOffset = typeof offset === 'number' ? offset : 0;
 
-    // Request one extra row to detect if there are more results
-    const paginatedSql = `SELECT * FROM (${sql.replace(/;+\s*$/, '')}) AS __paginated_query LIMIT ${pageLimit + 1} OFFSET ${pageOffset}`;
+      // Request one extra row to detect if there are more results
+      const paginatedSql = `SELECT * FROM (${sql.replace(/;+\s*$/, '')}) AS __paginated_query LIMIT ${pageLimit + 1} OFFSET ${pageOffset}`;
 
-    const result = await service.execute(paginatedSql);
+      const result = await service.execute(paginatedSql);
 
-    // Check if there are more results
-    const hasMore = result.rows.length > pageLimit;
-    if (hasMore) {
-      result.rows = result.rows.slice(0, pageLimit);
-      result.rowCount = pageLimit;
-    }
+      // Check if there are more results
+      const hasMore = result.rows.length > pageLimit;
+      if (hasMore) {
+        result.rows = result.rows.slice(0, pageLimit);
+        result.rowCount = pageLimit;
+      }
 
-    res.json({
-      ...result,
-      hasMore,
-    });
+      res.json({
+        ...result,
+        hasMore,
+      });
+    } else {
+      // DDL, DML, and other non-SELECT statements: execute directly without pagination
+      const result = await service.execute(sql);
+      res.json({
+        ...result,
+        hasMore: false,
+      });
+    }
   } catch (error) {
     const message = error instanceof Error ? error.message : 'Query execution failed';
     res.status(500).json({ error: message });