Hibernate ORM exposes SchemaManager.truncate() (via session.getSchemaManager().truncateMappedObjects()) as a public API for clearing all data from mapped tables while preserving the schema. Applications use this for admin data-reset workflows, multi-tenant data cleanup, and integration test harnesses.

For MongoDB, this operation is semantically equivalent to calling deleteMany({}) on each mapped collection.

Current Behavior

MongoDialect does not override getTruncateTableStatements() or getTableCleaner() from the base Dialect class. The default implementation returns SQL strings like 'truncate table <tableName>', which are not valid MQL. When executed, the MongoDB JDBC driver fails to parse them, the exception is caught by Hibernate's schema management layer, a warning is logged, and execution continues. No data is removed and no error is surfaced to the caller.

Proposed Fix

Override getTruncateTableStatements(String[] tableNames) in MongoDialect to emit a MongoDB delete command per collection:

{"delete": "<collectionName>", "deletes": [{"q": {}, "limit": 0}]}

This matches TRUNCATE semantics (remove all documents, preserve collection structure and indexes) using valid MQL.