Re: LMDB: issue with mdb_cursor_del

[timur.kristof@gmail.com]

On Mon, 2017-10-16 at 11:51 +0100, Howard Chu wrote:
> > 
> > It appears that it couldn't mark a page as dirty.
> > Here is the relevant assertion from mdb_page_dirty:
> > rc = insert(txn->mt_u.dirty_list, &mid);
> > mdb_tassert(txn, rc == 0); // assertion failed
> > 
> > What might I be doing wrong in my application that triggers this
> > sort
> > of error?
> 
> Take a look at the value of rc, then look in midl.c.

I've taken a look.
The value of rc is -1, which according to the mdb_mid2l_insert code
means that it's a duplicate value, so the page is already in the txn's
dirty pages list.

Since it comes from an mdb_page_alloc call, it is a bit weird that the
newly allocated page is already on the list, but maybe it's a reused
page?

>  Most likely the dirty 
> list is too big, which means you're trying to do too much in a single
> transaction.

The code did work on the compacted database, and it was doing exactly
the same operations on it, so this was unlikely.

- Timur