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The verbose query logs at logLevel 5 can prove immensely helpful for understanding how a query is executing. We should do a pass in order to clean up what information we generate, and also to make logLevel 4 useful. Currently, operators of live systems may wish to enable verbosity 0 or 1 for the query log component. Developers may wish to enable verbosity 5. However, levels 2-4 are rarely useful.
The "query" log component at logLevel 4 should give some high-level detail about the steps the planner is taking in order to plan a query. It should provide the following:
- The parsed query.
- The tagged and "rated" MatchExpression tree.
- The candidate plans generated, and their scores.
- An indication of which plan won.
At logLevel 5, we may provide additional details from each planning step. For instance, verbosity 5 may generate messages describing some of the details of predicate assignment in the access planner or details of covering analysis in the PlannerAnalysis step.
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