> 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.