PostgreSQL Query Evaluation (cont)
Each executable query is represented by a PlannedStmt node
- defined in
src/include/nodes/plannodes.h
- contains information for execution of query, e.g.
- which relations are involved, output tuple struecture, etc.
- most important component is a tree of
Plan nodes
Each Plan node represents one relational operation
- types:
SeqScan, IndexScan, HashJoin, Sort, ...
- each
Plan node also contains cost estimates for operation
|
![[prev]](icon/prev.gif){kind=icon}
![[next]](icon/next.gif){kind=icon}