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: Konstantin Knizhnik <k.knizhnik@postgrespro.ru>
Cc: pgsql-hackers@postgresql.org
Date: 2017-09-04T20:52:04Z
Lists: pgsql-hackers 
Hi,

On 2017-09-04 20:01:03 +0300, Konstantin Knizhnik wrote:
> > I previously had an early prototype of JITing [1] expression evaluation
> > and tuple deforming.  I've since then worked a lot on this.
> > 
> > Here's an initial, not really pretty but functional, submission. This
> > supports all types of expressions, and tuples, and allows, albeit with
> > some drawbacks, inlining of builtin functions.  Between the version at
> > [1] and this I'd done some work in c++, because that allowed to
> > experiment more with llvm, but I've now translated everything back.
> > Some features I'd to re-implement due to limitations of C API.
> > 
> > 
> > I've whacked this around quite heavily today, this likely has some new
> > bugs, sorry for that :(
> 
> Can you please clarify the following fragment calculating attributes
> alignment:

Hi. That piece of code isn't particularly clear (and has a bug in the
submitted version), I'm revising it.

> 
>         /* compute what following columns are aligned to */
> +        if (att->attlen < 0)
> +        {
> +            /* can't guarantee any alignment after varlen field */
> +            attcuralign = -1;
> +        }
> +        else if (att->attnotnull && attcuralign >= 0)
> +        {
> +            Assert(att->attlen > 0);
> +            attcuralign += att->attlen;
> +        }
> +        else if (att->attnotnull)
> +        {
> +            /*
> +             * After a NOT NULL fixed-width column, alignment is
> +             * guaranteed to be the minimum of the forced alignment and
> +             * length.  XXX
> +             */
> +            attcuralign = alignto + att->attlen;
> +            Assert(attcuralign > 0);
> +        }
> +        else
> +        {
> +            //elog(LOG, "attnotnullreset: %d", attnum);
> +            attcuralign = -1;
> +        }
> 
> 
> I wonder why in this branch (att->attnotnull && attcuralign >= 0)
> we are not adding "alignto" and comment in the following branch else if
> (att->attnotnull)
> seems to be not related to this branch, because in this case attcuralign is
> expected to be less then zero wjhich means that previous attribute is varlen
> field.

Yea, I've changed that already, although it's currently added earlier,
because the alignment is needed before, to access the column correctly.
I've also made number of efficiency improvements, primarily to access
columns with an absolute offset if all preceding ones are fixed width
not null columns - that is quite noticeable performancewise.


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".