[IMPALA-10936] StmtMetadataLoader::collectPolicyTables() should handle FailedLoadLocalTable without NPE

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 4.0.0
• Fix Version/s: Impala 4.1.0, Impala 4.0.1
• Component/s: Frontend
• Epic Color: ghx-label-13
• Assignee: Quanlong Huang
• Reporter: Joe McDonnell
• Created: 29/Sep/21 00:19
• Updated: 08/Oct/21 00:57
• Resolved: 08/Oct/21 00:55

Description

If table loading fails, then it result in a FailedLoadLocalTable, which uses this constructor for LocalTable:

  protected LocalTable(LocalDb db, String tblName) {
    this.db_ = Preconditions.checkNotNull(db);
    this.name_ = tblName;
    this.ref_ = null;
    this.msTable_ = null;
    this.cols_ = null;
    this.tableStats_ = null;
  }

Since cols_ and other fields are null, the code in StmtMetadataLoader::collectPolicyTables(), which calls LocalTable::getColumnsInHiveOrder() will throw a NullPointerException when trying to access cols_ in getNonClusteringColumns(). 

This will fail the query with a NullPointerException, even though the underlying problem came from failing to load the table metadata. We should handle this to avoid the NullPointerException. That may happen as part of StmtMetadataLoader::collectPolicyTables() or StmtMetadataLoader::getMissingTables().

Issue Links

• is caused by: IMPALA-10483 Support column-masking/row-filtering policy expressions that contain subqueries
• links to: Code Review