Horton

Re: automatically generating node support functions

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Peter Eisentraut <peter.eisentraut@enterprisedb.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2022-02-15T02:10:25Z
Lists: pgsql-hackers 
Hi,

On 2022-02-14 20:47:33 -0500, Tom Lane wrote:
> I think that most of the intellectual content in this patch is getting
> the data source nailed down, ie putting the annotations into the *nodes.h
> files and building the code to parse that.  I don't have a problem
> with throwing away and rewriting the back-end part of the patch later.

Imo that cuts the other way - without going for a metadata based approach we
don't know if we made the annotations rich enough...


> And, TBH, I am not really convinced that a pure metadata approach is going
> to work out, or that it will have sufficient benefit over just automating
> the way we do it now.  I notice that Peter's patch leaves a few
> too-much-of-a-special-case functions unconverted, which is no real
> problem for his approach; but it seems like you won't get to take such
> shortcuts in a metadata-reading implementation.

IMO my prototype of that approach pretty conclusively shows that it's feasible
and worthwhile.


> The bottom line here is that I believe that Peter's patch could get us out
> of the business of hand-maintaining the backend/nodes/*.c files in the v15
> timeframe, which would be a very nice thing.  I don't see how your patch
> will be ready on anywhere near the same schedule.  When it is ready, we can
> switch, but in the meantime I'd like the maintenance benefit.

I'm not going to try to prevent the patch from going in. But I don't think
it's a great idea to this without even trying to ensure the annotations are
rich enough...

Greetings,

Andres Freund

Commits

  1. Fix MSVC build script's check for obsolete node support functions.

  2. Improve performance of ORDER BY / DISTINCT aggregates

  3. doc: Fix typos in protocol.sgml

  4. Tighten up parsing logic in gen_node_support.pl.

  5. Add defenses against unexpected changes in the NodeTag enum list.

  6. Add copy/equal support for XID lists

  7. Rationalize order of input files for gen_node_support.pl.

  8. Make assorted quality-of-life improvements in gen_node_support.pl.

  9. Doc: rearrange high-level commentary about node support coverage.

  10. Automatically generate node support functions

  11. Adjust node serialization tag of A_Expr for consistency

  12. Remove T_Join and T_Plan

  13. Reformat some more node comments

  14. Reformat some node comments

  15. Remove JsonPathSpec typedef

  16. Add missing enum tag in enum used in nodes

  17. Add Cardinality typedef

  18. Make node output prefix match node structure name

  19. Add WRITE_INDEX_ARRAY

  20. Add COPY_ARRAY_FIELD and COMPARE_ARRAY_FIELD

  21. Remove T_Expr

  22. Change NestPath node to contain JoinPath node

  23. Change SeqScan node to contain Scan node

  24. Check the size in COPY_POINTER_FIELD

  25. Remove T_MemoryContext

  26. Add missing enum tags in enums used in nodes

  27. Rename some node support functions for consistency

  28. Rename argument of _outValue()

  29. Rename NodeTag of ExprState