Re: [PHP-PEAR] possible bug in DB/pgsql.php

On 20 Feb 2001, at 0:14, Stig S. Bakken wrote:

> [email protected] wrote:
> > 
> 
> Hi Fabrizio,
> 
> I was only joking about emulating. :-)
> 
Got me with the hook and all... :-)

> IMHO the "transaction visibility" issue is something to just keep on the
> radar for now.  We may want to do something about it later after testing
> if it _is_ possible to set up a consistent behaviour in all databases
> that support transactions.
> 
It will be a hairy matter. Since we were talking about this, I made a 
quick check with the development environment I have underhand; 
Though SQL92 standards recommends "serializable" isolation level 
as default, no one respected it. Of course it is made in the sake of 
performance, since serializable isolation means high number of 
locks for concurrent accesses, that's often undesirable - for web 
applications, for sure!!!
As I said, PG-Sql has 2 level of isolation and defaults to the weaker;
MS-SQL has 4 levels, and it defaults to the weaker also (and it's 
REALLY weak - it allows even "phantom data"); IBM DB2 7.0 has 4 
levels too, but I've not found a way to switch among them, nor 
which one is the default. I tend to think that it's an option 
accessible only at instance creation.

Don't know anything about other powerhouses like Oracle or 
Sybase, but this seems enough for me to think seriously to leave 
this thing out of DB :-)...

Best regards!


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Fabrizio Ermini               Alternate E-mail:
C.so Umberto, 7               [email protected]
loc. Meleto Valdarno          Mail on GSM: (keep it short!)
52020 Cavriglia (AR)          [email protected]