Horton

Re: JIT compiling expressions/deform + inlining prototype v2.0

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Greg Stark <stark@mit.edu>
Cc: Konstantin Knizhnik <k.knizhnik@postgrespro.ru>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2017-09-05T18:52:30Z
Lists: pgsql-hackers 
On 2017-09-05 19:43:33 +0100, Greg Stark wrote:
> On 5 September 2017 at 11:58, Konstantin Knizhnik
> <k.knizhnik@postgrespro.ru> wrote:
> >
> > I wonder if we can perform some optimization in this case (assuming that in
> > typical cases column either contains mostly non-null values, either mostly
> > null values).
> 
> If you really wanted to go crazy here you could do lookup tables of
> bits of null bitmaps. Ie, you look at the first byte of the null
> bitmap, index into an array and it points to 8 offsets for the 8
> fields covered by that much of the bitmap. The lookup table might be
> kind of large since offsets are 16-bits so you're talking 256 * 16
> bytes or 2kB for every 8 columns up until the first variable size
> column (or I suppose you could even continue in the case where the
> variable size column is null).

I'm missing something here. What's this saving?  The code for lookups
with NULLs after jitting effectively is
a) one load for every 8 columns (could be optimized to one load every
   sizeof(void*) cols)
b) one bitmask for every column + one branch for null
c) load for the datum, indexed by register
d) saving the column value, that's independent of NULLness
e) one addi adding the length to the offset

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".