Horton

Re: automatically generating node support functions

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Cc: Andres Freund <andres@anarazel.de>, David Rowley <dgrowleyml@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2022-07-11T15:37:39Z
Lists: pgsql-hackers 
Peter Eisentraut <peter.eisentraut@enterprisedb.com> writes:
> On 11.07.22 01:09, Tom Lane wrote:
>> Andres Freund <andres@anarazel.de> writes:
> I was just rebasing meson ontop of this and was wondering whether the input
> filenames were in a particular order:

> First, things used by later files need to be found in earlier files.  So 
> that constrains the order a bit.

Yeah, the script needs to see supertype nodes before subtype nodes,
else it will not realize that the subtypes are nodes at all.  However,
there is not very much cross-header-file subtyping.  I experimented with
rearranging the input-file order, and found that the *only* thing that
breaks it is to put primnodes.h after pathnodes.h (which fails because
PlaceHolderVar is a subtype of Expr).  You don't even need nodes.h to be
first, which astonished me initially, but then I realized that both
NodeTag and struct Node are special-cased in gen_node_support.pl,
so we know enough to get by even before reading nodes.h.

More generally, the main *nodes.h files themselves are arranged in
pipeline order, eg parsenodes.h #includes primnodes.h.  So that seems
to be a pretty safe thing to rely on even if we grow more cross-header
subtyping cases later.  But I'd vote for putting the incidental files
in alphabetical order.

> Second, the order of the files determines the ordering of the output. 
> The current order of the files reflects approximately the order how the 
> manual code was arranged.  That could be changed.  We could also just 
> sort the node types in the script and dump out everything alphabetically.

+1 for sorting alphabetically.  I experimented with that and it's a
really trivial change.

			regards, tom lane

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