Horton

tablecmds.c/MergeAttributes() cleanup

Peter Eisentraut <peter@eisentraut.org>

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From: Peter Eisentraut <peter@eisentraut.org>
To: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2023-06-28T16:30:14Z
Lists: pgsql-hackers

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The MergeAttributes() and related code in and around tablecmds.c is huge 
and ancient, with many things bolted on over time, and difficult to deal 
with.  I took some time to make careful incremental updates and 
refactorings to make the code easier to follow, more compact, and more 
modern in appearance.  I also found several pieces of obsolete code 
along the way.  This resulted in the attached long patch series.  Each 
patch tries to make a single change and can be considered incrementally. 
  At the end, the code is shorter, better factored, and I hope easier to 
understand.  There shouldn't be any change in behavior.

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