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d3ab5ff3e7
Create a shadow table. For `stats`, it'd be `_stats_rowgroups`. It contains three columns: - the clause (eg `city = 'Dawson Creek'`) - the initial estimate, as a bitmap of rowgroups based on stats - the actual observed rowgroups, as a bitmap This papers over poorly sorted parquet files, at the cost of some disk space. It makes interactive queries much more natural -- drilldown style queries are much faster, as they can leverage work done by previous queries. eg 'SELECT * FROM stats WHERE city = 'Dawson Creek' and question_id >= 1935 and question_id <= 1940` takes ~584ms on first run, but 9ms on subsequent runs. We only create entries when the estimates don't match the actual results. Fixes #6