To identify a tuple within the table, tuple identifier (TID) is internally used. A TID comprises a pair of values: the block number of the page that contains the tuple, and the offset number of the line pointer that points to the tuple. A typical example of its usage is index.
TID-Scan is a method that accesses a tuple directly by using TID of the desired tuple. For example, to find the 1st tuple in the 0-th page within the table, issue the following query:
sampledb=# SELECT ctid, data FROM sampletbl WHERE ctid = '(0,1)'; ctid | data -------+----------- (0,1) | AAAAAAAAA (1 row)标签：PostgreSQL,tuple,within,number,oracle,rowid,TID,ctid From： https://www.cnblogs.com/gwgwgw/p/16905505.html