new file: backend/src/controllers/schemaController.ts

new file:   backend/src/migrations/008_add_database_schemas.sql
	modified:   backend/src/routes/sqlInterface.ts
	modified:   frontend/package.json
	modified:   frontend/src/App.tsx
	modified:   frontend/src/components/Sidebar.tsx
	new file:   frontend/src/pages/DatabaseSchema.tsx
	modified:   frontend/src/services/api.ts

backend/src/controllers/schemaController.ts

@@ -0,0 +1,186 @@
+import { Request, Response } from 'express';
+import { mainPool } from '../config/database';
+import { databasePoolManager } from '../services/DatabasePoolManager';
+
+interface ColumnInfo {
+  name: string;
+  type: string;
+  nullable: boolean;
+  default_value: string | null;
+  is_primary: boolean;
+  comment: string | null;
+}
+
+interface ForeignKey {
+  column: string;
+  references_table: string;
+  references_column: string;
+  constraint_name: string;
+}
+
+interface TableInfo {
+  name: string;
+  schema: string;
+  comment: string | null;
+  columns: ColumnInfo[];
+  foreign_keys: ForeignKey[];
+}
+
+interface SchemaData {
+  tables: TableInfo[];
+  updated_at: string;
+}
+
+// Parse PostgreSQL schema
+async function parsePostgresSchema(databaseId: string): Promise<SchemaData> {
+  const pool = databasePoolManager.getPool(databaseId);
+  if (!pool) {
+    throw new Error('Database not found or not active');
+  }
+
+  // Get all tables
+  const tablesResult = await pool.query(`
+    SELECT
+      t.table_schema,
+      t.table_name,
+      obj_description((t.table_schema || '.' || t.table_name)::regclass, 'pg_class') as table_comment
+    FROM information_schema.tables t
+    WHERE t.table_schema NOT IN ('pg_catalog', 'information_schema')
+      AND t.table_type = 'BASE TABLE'
+    ORDER BY t.table_schema, t.table_name
+  `);
+
+  const tables: TableInfo[] = [];
+
+  for (const table of tablesResult.rows) {
+    // Get columns for each table
+    const columnsResult = await pool.query(`
+      SELECT
+        c.column_name,
+        c.data_type,
+        c.is_nullable,
+        c.column_default,
+        CASE WHEN pk.column_name IS NOT NULL THEN true ELSE false END as is_primary,
+        col_description((c.table_schema || '.' || c.table_name)::regclass, c.ordinal_position) as column_comment
+      FROM information_schema.columns c
+      LEFT JOIN (
+        SELECT ku.column_name, ku.table_schema, ku.table_name
+        FROM information_schema.table_constraints tc
+        JOIN information_schema.key_column_usage ku
+          ON tc.constraint_name = ku.constraint_name
+          AND tc.table_schema = ku.table_schema
+        WHERE tc.constraint_type = 'PRIMARY KEY'
+      ) pk ON c.column_name = pk.column_name
+          AND c.table_schema = pk.table_schema
+          AND c.table_name = pk.table_name
+      WHERE c.table_schema = $1 AND c.table_name = $2
+      ORDER BY c.ordinal_position
+    `, [table.table_schema, table.table_name]);
+
+    // Get foreign keys
+    const fkResult = await pool.query(`
+      SELECT
+        kcu.column_name,
+        ccu.table_name AS references_table,
+        ccu.column_name AS references_column,
+        tc.constraint_name
+      FROM information_schema.table_constraints tc
+      JOIN information_schema.key_column_usage kcu
+        ON tc.constraint_name = kcu.constraint_name
+        AND tc.table_schema = kcu.table_schema
+      JOIN information_schema.constraint_column_usage ccu
+        ON ccu.constraint_name = tc.constraint_name
+        AND ccu.table_schema = tc.table_schema
+      WHERE tc.constraint_type = 'FOREIGN KEY'
+        AND tc.table_schema = $1
+        AND tc.table_name = $2
+    `, [table.table_schema, table.table_name]);
+
+    tables.push({
+      name: table.table_name,
+      schema: table.table_schema,
+      comment: table.table_comment,
+      columns: columnsResult.rows.map(col => ({
+        name: col.column_name,
+        type: col.data_type,
+        nullable: col.is_nullable === 'YES',
+        default_value: col.column_default,
+        is_primary: col.is_primary,
+        comment: col.column_comment,
+      })),
+      foreign_keys: fkResult.rows.map(fk => ({
+        column: fk.column_name,
+        references_table: fk.references_table,
+        references_column: fk.references_column,
+        constraint_name: fk.constraint_name,
+      })),
+    });
+  }
+
+  return {
+    tables,
+    updated_at: new Date().toISOString(),
+  };
+}
+
+// Get cached schema or return null
+async function getCachedSchema(databaseId: string): Promise<SchemaData | null> {
+  const result = await mainPool.query(
+    'SELECT schema_data FROM database_schemas WHERE database_id = $1',
+    [databaseId]
+  );
+
+  if (result.rows.length > 0) {
+    return result.rows[0].schema_data as SchemaData;
+  }
+  return null;
+}
+
+// Save schema to cache
+async function saveSchemaToCache(databaseId: string, schemaData: SchemaData): Promise<void> {
+  await mainPool.query(`
+    INSERT INTO database_schemas (database_id, schema_data, updated_at)
+    VALUES ($1, $2, NOW())
+    ON CONFLICT (database_id)
+    DO UPDATE SET schema_data = $2, updated_at = NOW()
+  `, [databaseId, JSON.stringify(schemaData)]);
+}
+
+// GET /api/workbench/schema/:databaseId
+export const getSchema = async (req: Request, res: Response) => {
+  try {
+    const { databaseId } = req.params;
+
+    // Try to get from cache first
+    let schema = await getCachedSchema(databaseId);
+
+    if (!schema) {
+      // Parse and cache if not exists
+      schema = await parsePostgresSchema(databaseId);
+      await saveSchemaToCache(databaseId, schema);
+    }
+
+    res.json({ success: true, data: schema });
+  } catch (error: any) {
+    console.error('Error getting schema:', error);
+    res.status(500).json({ success: false, error: error.message });
+  }
+};
+
+// POST /api/workbench/schema/:databaseId/refresh
+export const refreshSchema = async (req: Request, res: Response) => {
+  try {
+    const { databaseId } = req.params;
+
+    // Parse fresh schema
+    const schema = await parsePostgresSchema(databaseId);
+
+    // Save to cache
+    await saveSchemaToCache(databaseId, schema);
+
+    res.json({ success: true, data: schema });
+  } catch (error: any) {
+    console.error('Error refreshing schema:', error);
+    res.status(500).json({ success: false, error: error.message });
+  }
+};