Horton

Re: JIT & function naming

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers@postgresql.org
Date: 2017-09-03T18:25:16Z
Lists: pgsql-hackers 
On 2017-09-03 10:11:37 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > Currently there's essentially a per EState counter and the generated
> > functions get named deform$n and evalexpr$n. That allows for profiling
> > of a single query, because different compiled expressions are
> > disambiguated. It even allows to run the same query over and over, still
> > giving meaningful results.  But it breaks down when running multiple
> > queries while profiling - evalexpr0 can mean something entirely
> > different for different queries.
> 
> > The best idea I have so far would be to name queries like
> > evalexpr_$fingerprint_$n, but for that we'd need fingerprinting support
> > outside of pg_stat_statement, which seems painful-ish.
> 
> Yeah.  Why not just use a static counter to give successive unique IDs
> to each query that gets JIT-compiled?  Then the function names would
> be like deform_$querynumber_$subexprnumber.

That works, but unfortunately it doesn't keep the names the same over
reruns. So if you rerun the query inside the same session - a quite
reasonable thing to get more accurate profiles - the names in the
profile will change. That makes it quite hard to compare profiles,
especially when a single execution of the query is too quick to see
something meaningful.

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".