Re: LMDB mdb_dbi_open mystery

[Howard Chu <hyc@symas.com>]

Sam Dave wrote:
> Thanks for the reply.
> 
> That's what it says on its own, but the doc also says:
> 
> * The database handle will be private to the current transaction until
> * the transaction is successfully committed. If the transaction is
> * aborted the handle will be closed automatically.
> * After a successful commit the handle will reside in the shared
> * environment, and may be used by other transactions.
> 
> That suggests I have to wait for a transaction to finish before I can reuse the same db handle for other transactions.

No, that's not at all what it says.

*Opening* a DBI handle can only be done by one transaction. *Using* an open DBI handle
can be done by any transactions.

> How would you in practice perform multiple transactions at the same time? I don't see it yet. I'm missing something basic.
> 
> 
> Feb 11, 2019, 5:50 AM by hyc@symas.com:
> 
>     Sam Dave wrote:
> 
>         Hello,
> 
>         The doc for mdb_dbi_open says:
> 
>         * This function must not be called from multiple concurrent
>         * transactions in the same process. A transaction that uses
>         * this function must finish (either commit or abort) before
>         * any other transaction in the process may use this function.
> 
>         This indicates that each process can only perform one transaction at the same time.
> 
> 
>     No, it only says you may only call mdb_dbi_open from one transaction at a time.
> 
>         This makes sense for write transactions, but wasn't LMDB supposed to support multiple read transactions at the same time?
> 
>         I'm a bit confused now. Can you assist?
> 
>         Thanks,
>         Sam
> 
> 
> 
>     -- 
>     -- Howard Chu
>     CTO, Symas Corp. http://www.symas.com
>     Director, Highland Sun http://highlandsun.com/hyc <http://highlandsun.com/hyc/>
>     Chief Architect, OpenLDAP http://www.openldap.org/project <http://www.openldap.org/project/>
> 
> 


-- 
  -- Howard Chu
  CTO, Symas Corp.           http://www.symas.com
  Director, Highland Sun     http://highlandsun.com/hyc/
  Chief Architect, OpenLDAP  http://www.openldap.org/project/