Horton

Re: JIT compiling with LLVM v11

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2018-03-11T18:25:21Z
Lists: pgsql-hackers 
On 2018-03-11 13:19:57 -0400, Peter Eisentraut wrote:
> On 3/9/18 15:56, Andres Freund wrote:
> > I think that's largely that unnecessary trivial queries get JITed and
> > optimized, because the stats are entirely completely off.
> 
> Right.  I instrumented this a bit, and there are indeed two handfuls of
> queries that exceed the default JIT thresholds, as well as a few that
> trigger JIT because they disable some enable_* planner setting, as
> previously discussed.
> 
> Should we throw in some ANALYZEs to avoid this?

Hm, I'd actually lean to just leave it as is for now. JITing halfway
random queries isn't actually that bad... If we get fed up with the
additional time after a while, we can do something then?


> It's perhaps a bit confusing that some of the jit_* settings take effect
> at plan time and some at execution time.  At the moment, this mainly
> affects me reading the code ;-), but it would also have some effect on
> prepared statements and such.

Not quite sure what you mean?


> Also, jit_tuple_deforming is apparently used only when jit_expressions
> is on.

Right. I've not found a good place to hook into that has enough context
to do JITed deforming otherwise.  I'm inclined to just relegate
jit_tuple_deforming to debugging status (i.e. exclude from show all,
docs etc) for now.


> So, we should work toward more clarity on all these different settings,
> what they are useful for, when to set them, how they interact.

Yep.

Greetings,

Andres Freund

Commits

  1. Improve JIT docs.

  2. Add documentation for the JIT feature.

  3. Add EXPLAIN support for JIT.

  4. Add inlining support to LLVM JIT provider.

  5. JIT tuple deforming in LLVM JIT provider.

  6. Add FIELDNO_* macro designating offset into structs required for JIT.

  7. Add expression compilation support to LLVM JIT provider.

  8. Expand list of synchronized types and functions in LLVM JIT provider.

  9. Add helpers for emitting LLVM IR.

  10. Basic planner and executor integration for JIT.

  11. Debugging and profiling support for LLVM JIT provider.

  12. Support for optimizing and emitting code in LLVM JIT provider.

  13. Add file containing extensions of the LLVM C API.

  14. Basic JIT provider and error handling infrastructure.

  15. Add configure infrastructure (--with-llvm) to enable LLVM support.

  16. Add C++ support to configure.

  17. Add PGAC_PROG_VARCC_VARFLAGS_OPT autoconf macro.

  18. Fix VM buffer pin management in heap_lock_updated_tuple_rec().

  19. Allow tupleslots to have a fixed tupledesc, use in executor nodes.

  20. Expression evaluation based aggregate transition invocation.

  21. Perform slot validity checks in a separate pass over expression.

  22. Rely on executor utils to build targetlist for DML RETURNING.

  23. Refer to OS X as "macOS", except for the port name which is still "darwin".