Horton

Re: tablecmds.c/MergeAttributes() cleanup

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Peter Eisentraut <peter@eisentraut.org>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2024-01-12T15:09:41Z
Lists: pgsql-hackers 
On Fri, Jan 12, 2024 at 5:32 AM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> On 2024-Jan-11, Alvaro Herrera wrote:
> > If you look closely at InsertPgAttributeTuples and accompanying code, it
> > all looks a bit archaic.  They seem to be treating TupleDesc as a
> > glorified array of Form_pg_attribute elements in a convenient packaging.
> > It's probably cleaner to change these APIs so that they deal with a
> > Form_pg_attribute array, and not TupleDesc anymore.  But we can hack on
> > that some other day.
>
> In addition, it also occurs to me now that maybe it would make sense to
> change the TupleDesc implementation to use a List of Form_pg_attribute
> instead of an array, and do away with ->natts.  This would let us change
> all "for ( ... natts ...)" loops into foreach_ptr() loops ...  there are
> only five hundred of them or so --rolls eyes--.

Open-coding stuff like this can easily work out to a loss, and I
personally think we're overly dependent on List. It's not a
particularly good abstraction, IMHO, and if we do a lot of work to
start using it everywhere because a list is really an array, then what
happens when somebody decides that a list really ought to be a
skip-list, or a hash table, or some other crazy thing?

-- 
Robert Haas
EDB: http://www.enterprisedb.com

Commits

  1. Fix segmentation fault in MergeInheritedAttribute()

  2. Improve compression and storage support with inheritance

  3. Split some code out from MergeAttributes()

  4. MergeAttributes code deduplication

  5. Add a const decoration

  6. MergeAttributes: convert pg_attribute back to ColumnDef before comparing

  7. Refactor ATExecAddColumn() to use BuildDescForRelation()

  8. Move BuildDescForRelation() from tupdesc.c to tablecmds.c

  9. Push attcompression and attstorage handling into BuildDescForRelation()

  10. Push attidentity and attgenerated handling into BuildDescForRelation()

  11. Add TupleDescGetDefault()

  12. MergeAttributes() and related variable renaming

  13. Clean up MergeCheckConstraint()

  14. Clean up MergeAttributesIntoExisting()

  15. Remove useless if condition

  16. Make more use of makeColumnDef()

  17. Add some const decorations

  18. Remove ancient special case code for dropping oid columns

  19. Remove ancient special case code for adding oid columns

  20. Remove obsolete comment about OID support