[elephant-devel] Re: Postmodern, Act II

[Alex Mizrahi]

 ??>> can you catch a backtrace? it seems to be quite relevant here

 LPP>  6: (LAMBDA NIL)
 LPP>     At
 LPP> /home/sky/projects/mystic/hg.beta1/packages/elephant/src/db-postmodern
 LPP> /pm-sql.lisp:1577: (LAMBDA NIL)
 LPP>     At
 LPP> /home/sky/projects/mystic/hg.beta1/packages/elephant/src/db-postmodern
 LPP> /pm-btree.lisp:2638: (SB-PCL::FAST-METHOD 
ELEPHANT::EXECUTE-TRANSACTION
 LPP> (DB-POSTMODERN::POSTMODERN-STORE-CONTROLLER
 LPP>  T))
 LPP>     At
 LPP> /home/sky/projects/mystic/hg.beta1/packages/elephant/src/db-postmodern
 LPP> /pm-transaction.lisp: 60
 LPP>     Local variables:
 LPP>       ARG-0 = 8
 LPP>       ARG-3 = #<POSTMODERN-STORE-CONTROLLER (POSTGRESQL 127.0.0.1
 LPP> mystic-world mystic mystic PORT
 LPP> 5433)>
 LPP>       ARG-4 = #<CLOSURE (LAMBDA NIL) {BA0738D}>
 LPP>  9: (SB-PCL::FAST-METHOD (SETF DB-POSTMODERN::INTERNAL-GET-VALUE) (T T
 LPP> DB-POSTMODERN::PM-BTREE))

it seems you didn't wrap your code into explicit transaction.

transaction was started implicitly by (setf internal-get-value) before 
writing to database, but cache update was done outside transaction, so it 
was not initialized properly.
fix is quite simple -- moving all txn functions inside that implicit 
transactions.

but if you do not start your transactions explicitly, enclosing as many 
operations as posible, global-sync-cache absolutely makes no sense -- it 
takes more effort to synchornize changes than to actually load value from 
database, if that's just a single value.

so, maybe, if cache is set into global sync mode, it should signal error if 
there is no explicit transactions -- because that would be misuse of global 
sync cache, leading to significant overhead.
or you think it makes sense to allow such behaviour? it might make sense in 
REPL, for example..