Execution of Transactions
Transactions deal with three address spaces:
- stored data on the disk
(representing global DB state)
- data in memory buffers
(where held for sharing by tx's)
- data in their own local variables
(where manipulated)
Each of these may hold a different "version" of a DB object.
PostgreSQL processes make heavy use of shared buffer pool
⇒ transactions do not deal with much local data.
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