On Sun, Feb 26, 2023 at 8:36 AM jack...@gmail.com <jack...@gmail.com> wrote:
> > CID means "command ID" i.e. sequential ID assigned to commands in a > > single session (for visibility checks, so that a query doesn't see data > > deleted by earlier commands in the same session). See > > src/backend/utils/time/combocid.c for basic explanation of what "combo > > CID" is. > I think if cid is used for visibility checks in one session, that's > meaingless, beacause we can use the t_xmin and t_xmax to > get this goal. Is tis > > I think the word "session" is wrong. It should be "transaction". IIUC, it is what is changed when one issues CommandCounterIncrement within a transaction. And you need somewhere to save which CCI step deletes rows, in particular due to the savepoint feature. David J.
