Wiki / OID 类型

Another identifier type used by the system is xid , or transaction (abbreviated xact ) identifier. This is the data type of the system columns xmin and xmax . Transaction identifiers are 32-bit quantities. In some contexts, a 64-bit variant xid8 is used. Unlike xid values, xid8 values increase strictly monotonically and cannot be reused in the lifetime of a database cluster. See Section 67.1 for more details.

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System columns

xmin, xmax