Hi Sorry for the delay.
> Is there a practical difference between READ_COMMITTED and REPEATABLE_READ in MVCC mode? H2 only supports READ_COMMITTED currently, as documented in http://h2database.com/html/advanced.html?highlight=Mvcc&search=MVCC#mvcc "Connections only 'see' committed data, and own changes. That means, if connection A updates a row but doesn't commit this change yet, connection B will see the old value. Only when the change is committed, the new value is visible by other connections (read committed)". > Does H2 implement Serializable Snapshot Currently not, and I didn't plan to support it. In theory, it could be supported with the MVStore, but I don't currently think it's very important. Regards, Thomas On Sat, Aug 24, 2013 at 8:10 PM, Gili <[email protected]> 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 <[email protected]> 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 >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "H2 Database" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> To post to this group, send email to [email protected]. >>> Visit this group at http://groups.google.com/group/h2-database. >>> For more options, visit https://groups.google.com/groups/opt_out. >>> >>> >>> >> >> -- >> You received this message because you are subscribed to a topic in the >> Google Groups "H2 Database" group. >> To unsubscribe from this topic, visit https://groups.google.com/d/ >> topic/h2-database/bGNuMpLr8IY/unsubscribe. >> To unsubscribe from this group and all its topics, send an email to >> [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at http://groups.google.com/group/h2-database. >> For more options, visit https://groups.google.com/groups/opt_out. >> >> >> >> >> -- > You received this message because you are subscribed to the Google Groups > "H2 Database" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/h2-database. > For more options, visit https://groups.google.com/groups/opt_out. > -- You received this message because you are subscribed to the Google Groups "H2 Database" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/h2-database. For more options, visit https://groups.google.com/groups/opt_out.
