Horton

automatically generating node support functions

Peter Eisentraut <peter.eisentraut@enterprisedb.com>

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From: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
To: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2021-06-07T20:27:52Z
Lists: pgsql-hackers

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I wrote a script to automatically generate the node support functions 
(copy, equal, out, and read, as well as the node tags enum) from the 
struct definitions.

The first eight patches are to clean up various inconsistencies to make 
parsing or generation easier.

The interesting stuff is in patch 0009.

For each of the four node support files, it creates two include files, 
e.g., copyfuncs.inc1.c and copyfuncs.inc2.c to include in the main file. 
  All the scaffolding of the main file stays in place.

In this patch, I have only ifdef'ed out the code to could be removed, 
mainly so that it won't constantly have merge conflicts.  Eventually, 
that should all be changed to delete the code.  When we do that, some 
code comments should probably be preserved elsewhere, so that will need 
another pass of consideration.

I have tried to mostly make the coverage of the output match what is 
currently there.  For example, one could do out/read coverage of utility 
statement nodes easily with this, but I have manually excluded those for 
now.  The reason is mainly that it's easier to diff the before and 
after, and adding a bunch of stuff like this might require a separate 
analysis and review.

Subtyping (TidScan -> Scan) is supported.

For the hard cases, you can just write a manual function and exclude 
generating one.

For the not so hard cases, there is a way of annotating struct fields to 
get special behaviors.  For example, pg_node_attr(equal_ignore) has the 
field ignored in equal functions.

There are a couple of additional minor issues mentioned in the script 
source.  But basically, it all seems to work.

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