Does anybody know? (Sorry for the bump) If I've asked something too stupid/newbie-ish, anyone welcome to let me know.
Jul 5, 2023, 17:43 by samd...@tuta.io: > I'll rephrase. > > For mdb_env_close: "Only a single thread may call this function". Is the > meaning same as "For each environment, this function can be called at most > once (from any thread)."? > > For mdb_dbi_close: "> This call is not mutex protected. > Handles should only > be closed by a single thread". Is the meaning same as "For each handle, this > function can be called at most once (from any thread). If you want to close > different handles on the same environment from different threads, you need to > synchronize their use."? > > If someone can confirm my understanding (or correct if wrong), I'd appreciate > it. > > > Jul 2, 2023, 09:46 by samd...@tuta.io: > >> Thanks, knowing that (complete independence of environments) makes things >> easier. >> >> Some follow-ups for clarification, >> >> * Why did "Only a single thread may call this function" have to be mentioned >> at all for mdb_env_close? It can afaik only be called at most once per >> environment anyway. (It seems implied by "The environment handle will be >> freed and must not be used again after this call", and sort of too from the >> caveats about opening an environment on disk only once). >> >> * About mdb_dbi_close, to "Handles should only be closed by a single >> thread", would it be worth it to add something like "or mdb_dbi_close should >> be synchronized, if called from multiple threads" ? >> >> - Sam >> >> Jul 1, 2023, 17:32 by h...@symas.com: >> >>> Sam Dave wrote: >>> >>>> Hi, >>>> >>>> I'm interested in understanding these functions better. These are not >>>> criticisms.. since these functions are called rarely, I have no problem >>>> synchronizing >>>> them. I ask only for curiosity's sake. >>>> >>> >>> Everything in LMDB is defined within the context of a single environment. >>> That should already be clear from the documentation. >>> >>> The constraints you reference below only apply within a single environment. >>> Separate environments are completely independent of each other. >>> >>>> >>>> * mdb_env_close: "Only a single thread may call this function." Why can't >>>> different environments (separate files/dirs on disk) be closed from >>>> different threads? >>>> >>>> * mdb_dbi_close: "Handles should only be closed by a single thread." Why >>>> can't at least databases on different environments (separate files/dirs on >>>> disk) be >>>> closed from different threads? >>>> >>>> * mdb_dbi_open: "This function must not be called from multiple concurrent >>>> transactions in the same process." Why can't this function be called from >>>> different >>>> threads to open at least databases on different environments (separate >>>> files/dirs on disk)? >>>> >>>> What are the reasons for these limitations, under the hood? Could these >>>> functions have been designed in a different way, to allow for more >>>> multithreading >>>> (again, I'm not asking for this, I'm just curious). >>>> >>>> - Sam >>>> >>> >>> >>> -- >>> -- Howard Chu >>> CTO, Symas Corp. http://www.symas.com >>> Director, Highland Sun http://highlandsun.com/hyc/ >>> Chief Architect, OpenLDAP http://www.openldap.org/project/ >>> >> >> > >
