Regards,
Thomas
On Sat, Aug 24, 2013 at 8:10 PM, Gili <cow...@bbs.darktech.org
<mailto:cow...@bbs.darktech.org>> wrote:
Thomas,
Can you please clarify how H2's implementation of MVCC
interacts with Transaction Isolation?
1. Is there a practical difference between READ_COMMITTED
and REPEATABLE_READ in MVCC mode? Doesn't MVCC prevent
READ_COMMITTED from seeing updates committed by other
transactions (after the current transaction has already
read the row once)? If so, aren't they identical?
2. Same question for REPEATABLE_READ and SERIALIZABLE
isolation in MVCC mode.
3. Does H2 implement
http://en.wikipedia.org/wiki/Serializable_Snapshot_Isolation#Serializable_Snapshot_Isolation
for
MVCC? If not, do you plan on doing so in the future?
Thank you,
Gili
On Sunday, June 23, 2013 11:23:16 AM UTC-4, Gili wrote:
Thanks Thomas. So you're saying I can use other
isolation modes with MVCC as I normally would?
Gili
On 23/06/2013 7:39 AM, Thomas Mueller wrote:
Hi,
H2 only supports row level locks when using the MVCC
mode. By the way, the plan is that in the future (with
the MVStore), the MVCC mode will be the default mode.
Insert/delete operations don't wait for other
operations that do not conflict. They wait for
conflicting operations (changes on the same rows).
> What happens in the following scenario?
H2 uses "read committed" by default, so T1 will see the
value from T2.
Regards,
Thomas
On Thu, Jun 20, 2013 at 8:18 PM, Gili
<cow...@bbs.darktech.org
<mailto:cow...@bbs.darktech.org>> wrote:
Hi,
Looking at
http://www.h2database.com/html/advanced.html#mvcc,
1. Does H2 only support table locks or MVCC? Or is
there a way to get row locks without MVCC?
2. Using MVCC, do insert/delete operations wait
until all open transactions complete?
3. Does this imply that open transactions will
never experience insert/delete rows by other
threads in mid-transaction?
4. What happens in the following scenario?
Database contains a single row: count[value=1]
T1: Open transaction
T2: Open transaction
T2: update count set value=2 where value=1
T2: commit
T1: select value from count
Will T1 see a value of 1 or 2?
Thanks,
Gili
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