# Overview Of Preprocessing Stages
+ Optimizer preprocessing
  + Optimized for PointGet
  + Construct the initial logical execution plan
    + constant folding
    + Expression simplification
    + Subquery processing

+ Preprocessing stage ——> Logical optimization stage ——> Physical optimization stage

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Overview of preprocessing stages
When Parser parses the SQL text into a syntax tree (AST), the first step is to perform preprocessing optimization. The purpose of preprocessing optimization is to get an initial logical execution plan. In the preprocessing optimization phase, two main things were done. The first thing was to optimize for spot checks. For non-spot request, we constructed a logical execution plan.