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On 10/14/06 14:35, Michael Fuhr wrote:
> On Sat, Oct 14, 2006 at 11:35:12AM -0700, Joshua D. Drake wrote:
>> What is the use case for a READ ONLY transaction?
>
> I use read-only transactions as a safety net for interactive sessions
> when I want to avoid modifying anything accidentally. Here's an
> example:
>
> CREATE ROLE foo LOGIN PASSWORD 'password';
> CREATE ROLE foo_ro LOGIN PASSWORD 'password';
> ALTER ROLE foo_ro SET default_transaction_read_only TO on;
> GRANT foo TO foo_ro;
>
> The foo_ro role now has the same privileges as foo but it can't
> modify anything because its transactions are read-only by default.
Another benefit (with ISOLATION LEVEL SERIALIZABLE) is that you are
guaranteed to have unchanging source data, no matter how many ways
you aggregate, join and WHERE it.
As Tom notes, other RDBMSs do pre-query optimizations. SET TRANS
READ ONLY tells the engine that these statements won't have to take
out concurrent write locks, and can thus take a different, faster
code path.
- --
Ron Johnson, Jr.
Jefferson LA USA
Is "common sense" really valid?
For example, it is "common sense" to white-power racists that
whites are superior to blacks, and that those with brown skins
are mud people.
However, that "common sense" is obviously wrong.
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