import { DatabaseService } from './database-service.js';
import { DatabaseConnection } from '../types.js';
export class DataMigrationService {
constructor(
private source: DatabaseService,
private target: DatabaseService
) {}
async migrateTable(tableName: string, targetTableName?: string, batchSize: number = 1000): Promise<{ rows: number, time: number }> {
const start = Date.now();
const targetName = targetTableName || tableName;
// 1. Describe source to know columns
const columns = await this.source.describeTable(tableName);
const colNames = columns.map(c => c.name);
// 2. Read data (Simulated stream via simple query for MVP)
// In production, this should be a true stream/cursor.
// Here we fetch up to 10000 rows.
const sql = `SELECT ${colNames.join(', ')} FROM ${tableName}`;
// Using a large limit for MVP migration
const result = await this.source.executeQuery(sql, 100000);
const rows = result.rows;
if (rows.length === 0) {
return { rows: 0, time: Date.now() - start };
}
// 3. Insert in batches
let totalInserted = 0;
for (let i = 0; i < rows.length; i += batchSize) {
const batch = rows.slice(i, i + batchSize);
// Basic Type Transformation (Mapping dates etc if needed)
// Currently insertBatch in DatabaseService handles basic insertion logic
await this.target.insertBatch(targetName, batch);
totalInserted += batch.length;
}
return {
rows: totalInserted,
time: Date.now() - start
};
}
async migrateData(tables: string[], truncateTarget: boolean = false): Promise<any> {
const results: any[] = [];
for (const table of tables) {
if (truncateTarget) {
// TODO: Implement truncate in DatabaseService
// await this.target.truncateTable(table);
}
try {
const res = await this.migrateTable(table);
results.push({ table, status: 'success', rows: res.rows, time: res.time });
} catch(e: any) {
results.push({ table, status: 'error', error: e.message });
}
}
return results;
}
}
