Thread: Understanding transactions

Understanding transactions

From
Jonathan Gardner
Date:
Seeing how PITR, nested transactions, and other exciting developments 
related to transactions are being developed, I am getting curious about how 
PostgreSQL actually implements transactions. Investigating Materialized 
Views has led me to look closely at how transactions work and such.

Do you know of good resources on learning how transactions are implemented 
in PostgreSQL? Should I just peruse the code? Which files are most 
relevant?

-- 
Jonathan Gardner
jgardner@jonathangardner.net


Re: Understanding transactions

From
Alvaro Herrera
Date:
On Thu, Jun 03, 2004 at 05:38:21PM -0700, Jonathan Gardner wrote:

> Do you know of good resources on learning how transactions are implemented 
> in PostgreSQL? Should I just peruse the code? Which files are most 
> relevant?

backend/access/transam/xact.c (high level transaction status) and
backend/utils/time/tqual.c (low level tuple visibility test --- this is
hard to read and understand) and its respective header files are the most
relevant.  See also htup.h about "heap tuples," specially heap tuple
headers and the games with Xmin, Xmax, Cmin and Cmax.


Not sure about other literature.  Make sure you understand how MVCC
works before reading the code ...

-- 
Alvaro Herrera (<alvherre[a]dcc.uchile.cl>)
Y dijo Dios: "Que sea Satanás, para que la gente no me culpe de todo a mí."
"Y que hayan abogados, para que la gente no culpe de todo a Satanás"



Re: Understanding transactions

From
Jochem van Dieten
Date:
Jonathan Gardner wrote:
> Seeing how PITR, nested transactions, and other exciting developments 
> related to transactions are being developed, I am getting curious about how 
> PostgreSQL actually implements transactions. Investigating Materialized 
> Views has led me to look closely at how transactions work and such.
> 
> Do you know of good resources on learning how transactions are implemented 
> in PostgreSQL? Should I just peruse the code? Which files are most 
> relevant?

Next to diving into the code you might want to dive into the 
theory. Chapter 5 of "Concurrency Control and Recovery in 
Database Systems" deals with Multi Version Concurrency Control: 
http://research.microsoft.com/pubs/ccontrol/

Jochem