Re: reusing transactions in LMDB

[Howard Chu <hyc@symas.com>]

Tim Uckun wrote:
> Hi.
>
> Sorry for being so dense but...

> The document says
>
> The transaction handle is freed. It and its cursors must not be used again
> after this call, except with mdb_cursor_renew().
>
>
> I am still very confused about reusing transactions.

Keep reading.

> If I commit or abort a read write transaction I can't reuse the transaction
> but I can re use the cursor? In the cursor documentation it says
>
>  Cursors that are only used in read-only transactions may be re-used, to avoid
> unnecessary malloc/free overhead.
>
> So this indicates only read only cursors can be reused right?

Yes.
> So can you confirm my understanding? This is what I get from reading the docs.
>
> A transaction can either be read write or read only.
>
> If a transaction is read only you can commit or abort the transaction and then
> re-open it again for further use.

No. Once a transaction is committed or aborted it is freed and cannot be 
reused. Period, end of story. Both the commit() and abort() docs are quite 
explicit about this.

> If a transaction is read write then it can't be used again after you commit or
> abort the transaction.
>
>
>
>
>
> On Tue, Nov 22, 2016 at 3:17 PM, Howard Chu <hyc@symas.com
> <mailto:hyc@symas.com>> wrote:
>
>     Tim Uckun wrote:
>
>
>
>             No. You can perform multiple write operations in a single transaction.
>
>
>         But once the commit has been called the next write operation has to be
>         a newly
>         opened transaction right?  The write transactions can't be re-opened.
>
>     http://lmdb.tech/doc/group__mdb.html#ga846fbd6f46105617ac9f4d76476f6597
>     <http://lmdb.tech/doc/group__mdb.html#ga846fbd6f46105617ac9f4d76476f6597>



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