Rerun catalog queries

Practical performance patterns for querying a Rerun catalog from Python (rerun.catalog.CatalogClient → dataset.reader(...) → DataFusion DataFrame). The DataFusion side of the stack is covered by the datafusion-python skill — load that for DataFrame / SessionContext / expression-API references. This skill focuses on catalog-specific behaviors and the round-trip costs that catch teams off guard.

The query cost model in one sentence

Every materialization of a dataset.reader(...) DataFrame is one cloud round-trip, with most of the cost being the network/decode pair, not the compute. Plan for round-trip count and payload bytes, in that order.