Hi, > Does MVCC even support different isolation modes?
Up to some point, yes, see http://www.postgresql.org/docs/9.3/static/transaction-iso.html Regards, Thomas On Mon, Nov 25, 2013 at 3:56 AM, Ryan How <[email protected]> wrote: > This is interesting :) > > Does MVCC even support different isolation modes?. I thought it was it's > own isolation mode? The different isolation modes don't seem to make sense > in an MVCC context? > > Thanks, Ryan > > > > On 24/11/2013 11:50 PM, cowwoc wrote: > > Hi Thomas, > > It was my understanding that SERIALIZABLE isolation in MVCC mode is > supposed to behave like SERIALIZABLE_SNAPSHOT. At least, that's the case > for Postgres. If SERIALIZABLE behaves the way you mention in MVCC mode, > what is the difference if MVCC mode is on or off? It doesn't sound like > there is a difference. > > Gili > > On 24/11/2013 7:49 AM, Thomas Mueller wrote: > > Hi, > > > How does SERIALIZABLE isolation in MVCC mode compare to > SERIALIZABLE_SNAPSHOT? Aren't they the same thing? > > I can only refer to Google, which found this: > http://blogs.msdn.com/b/craigfr/archive/2007/05/16/serializable-vs-snapshot-isolation-level.aspx > > Regards, > Thomas > > > > > On Sun, Nov 24, 2013 at 1:10 PM, cowwoc <[email protected]> wrote: > >> Hi Thomas, >> >> Thanks for the reply. >> >> >> On 21/11/2013 6:43 AM, Thomas Mueller wrote: >> >> > 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. >> >> >> How does SERIALIZABLE isolation in MVCC mode compare to >> SERIALIZABLE_SNAPSHOT? Aren't they the same thing? >> >> Thanks, >> Gili >> >> >> >> 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 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 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. > -- You received this message because you are subscribed to the Google Groups "H2 Database" group. 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