Re: nested transactions

Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > I should add that I am not prepared to overhaul the pg_clog file format
> > as part of adding subtransactions for 7.4.  I can do the tid/sequential scan
> > method for abort, or the single-lock method described.
> 
> If you think that changing the pg_clog file format would be harder than
> either of those other ideas, I think you're very badly mistaken.
> pg_clog is touched only by one rather simple module.

Agreed, the clog changes would be the simple solution.  However, I am
not sure I can make that level of changes.  In fact, the complexity of
having multiple transactions per backend is going to be tough for me
too.

Also, I should point out that balooning pg_clog by 16x is going to mean
we are perhaps 4-8x more likely to need extra pages to mark all
subtransactions.

Isn't there some other way we can link these subtransactions together
rather than mucking with pg_clog, as we only need the linkage while we
mark them all committed?

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