Trace data is received that was captured for an execution of a query on first tables when execution trouble occurs during an execution of the query on the first tables. Trace data includes counts of evaluation states caused by the execution and includes identifications of portions of the query that reference variables of the first tables and that correspond with the evaluation states. Second tables are generated from the evaluation state counts and the identifications of the trace data without accessing data values of the first tables, so that the first tables are kept private. Evaluation states are reproduced from the execution of the query on the first tables by executing the query on the second tables without accessing the data values of the first tables.