1.4 Planner: Which Path to Take
The article discusses the planner stage in PostgreSQL's query processing. It explains how the planner takes a Query tree and produces a PlannedStmt, determining the execution path based on cost estimates. The planner's decision-making process involves evaluating multiple candidates for execution strategies, focusing on efficiency rather than correctness.
- ▪The planner's role is to determine how to execute a query after the rewriter has processed it.
- ▪It evaluates different execution strategies based on estimated costs derived from statistics.
- ▪The planner consists of two layers: Path, which generates candidate routes, and Plan, which finalizes the chosen execution route.
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