05.05.2017 20:36, Adriano dos Santos Fernandes wrote: > On 05/05/2017 14:01, Vlad Khorsun :
... >> I don't understand for what purpose tra_oldest_snapshot was added. > In my understand, it's a property that new transaction should copy from > the base transaction. Isn't it? No. Re-evaluated value of OST is stored at jrd_trans::tra_oldest_active. > Should I let the original code assign it even for new transactions > that's sharing a snapshot? No. > But please read answear bellow, may be important for it. > > >> Also it is not clear why "base_number" variable is introduced in >> transaction_start() >> and why it replaces "number" in many places. > > When first normal (not with sharing snapshot option) transaction is > started, it must record others transaction snapshot until its own *number*. > > When second (with sharing snapshot option) transaction is started, > *number* has its new number too, but the snapshot vector must be record > only to the *base_number*, i.e., its snapshot vector should be identical > to the first transaction. If you worry about high bound of transaction's copy of TIP (tra_transactions) - it is already stored at jrd_trans::tra_top. BTW, transaction should export own snapshot at the end of transaction_start(), because it is the moment when all it fields got actual values (especially tra_oldest_active). Probably, transaction which import snapshot, should avoid recalculation of OIT and OST. At least, it should not update own tra_oldest_active with new value of OST. Regards, Vlad ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
