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Quantitative Finance · Glossário

O que é Query optimiser?

Definition 10.4 Research, Data and Risk Platforms · Capítulo 10 — Dataframes

A query optimiser rewrites a plan into an equivalent cheaper one before executing it: it pushes filters and projections toward the scans (so that fewer rows and columns are read, chapter 3), removes unused columns and operations, reorders joins and aggregations, and chooses algorithms.

A narrow query as written and as Polars executes it (from the plan it prints). The filter on the partition column removes 19 of 20 partitions before any file is opened; the projection keeps the two columns returned and the two the filter reads; the filter on the symbol runs inside the scan.
Figure 10.2. A narrow query as written and as Polars executes it (from the plan it prints). The filter on the partition column removes 19 of 20 partitions before any file is opened; the projection keeps the two columns returned and the two the filter reads; the filter on the symbol runs inside the scan.
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