Robert Hansen did a talk at OSCON on a compressed annealing framework
called Djinni: <>

It's a framework to use compressed annealing (a derivative of
simulated annealing) for finding approximate solutions to NP-complete
problems such as the TSP with time windows.  Note that while Djinni is
implemented in C++, it already supports embedding via SWIG, and has a
C wrapper and is accessible from other languages.  And it's

This has the potential to be an alternative to the present use of GEQO
for query optimization for cases of large joins (e.g. - involving
large numbers of tables).

On the one hand, I'm somewhat suited to looking at this in that I have
the operations research background to know what they're talking about.
On the other hand, I'm not familiar with the optimizer, nor do I deal
with sorts of cases with so many joins that this would be worthwhile.

I've bounced a ToDo entry over to Bruce, and am making sure this is
documented here on pgsql.hackers so that a web search can readily find
it in the future...
"It is far from complete, but it  should explain enough that you don't
just stare at your file like a deer staring at an oncoming
truck."  -- David Charlap

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TIP 9: In versions below 8.0, the planner will ignore your desire to
       choose an index scan if your joining column's datatypes do not

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