Re: (LMDB) read-only transactions and DBI handles

[Howard Chu <hyc@symas.com>]

Viacheslav Usov wrote:
> On Fri, Dec 11, 2015 at 2:51 PM, Howard Chu <hyc@symas.com
> <mailto:hyc@symas.com>> wrote:
>
>  > A DBI handle is simply a slot in an in-memory array. Read-only transactions
> are read-only with respect to the database.
>
> That is fine with me. It was you who tried to explain the DBI handles in terms
> of 'transactional databases" [1]. That explanation was problematic; copying
> your manner of speaking, one could say it was "utter nonsense".
>
> Can you clarify just this point: in sample-mdb.txt, a DBI handle is opened in
> the first transaction, which commits, and is used the second transaction,
> which aborts. What happens with the DBI handle when the second transaction
> aborts? Does it stay valid or does it get closed?

What happens when you write a record to the DB in the first transaction, which 
commits? When you start a second transaction, which aborts, does that record 
stay, or does it disappear?

What does the word "persist" mean?

Aborting a transaction only discards the operations that occurred within that 
transaction.

> There was another question in my
> message that you did not answer. I am copying it here for convenience.

And I am ignoring it, again.

> Can you confirm that, with read-only transactions, the only difference between
> commit and abort is in the way the associated DBI handles are treated, and,
> specifically, that no observable effect on performance will occur? If that is
> so, a note in the documentation stating this would be very helpful.
>
> Cheers,
> V.
>
> [1] Howard Chu: "Transactional databases are very simple"


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