Interpretation of PostgreSQL Source Code-MVCC#13 (vacuum procedure-vacuum_set_xid_limits function)

This section briefly introduces the processing flow of manual vacuum execution by PostgreSQL, and mainly analyzes the implementation logic of the ExecVacuum- > vacuum- > vacuum_rel- > heap_vacuum_rel- > vacuum_set_xid_limits function, which calculates the oldest xmin and freeze cutoff point.

I. data structure

Macro definition

Vacuum and Analyze command options

/ *-- * Vacuum and Analyze Statements * Vacuum and Analyze command options * * Even though these are nominally two statements, it's convenient to use * just one node type for both. Note that at least one of VACOPT_VACUUM * and VACOPT_ANALYZE must be set in options. Although there are two different statements here, you only need to use a uniform Node type. * Note that at least VACOPT_VACUUM/VACOPT_ANALYZE is set in the options. *-- * / typedef enum VacuumOption {VACOPT_VACUUM = 1