pgsql: Whole-row fixes for ALTER COLUMN SET EXPRESSION

Whole-row fixes for ALTER COLUMN SET EXPRESSION

When changing the expression of a generated column via ALTER TABLE
ALTER COLUMN SET EXPRESSION, objects that depend on the column via
indirect whole-row references (such as CHECK constraints, indexes)
must be handled specially, because technically pg_depend does not
contain such dependencies, see
recordDependencyOnSingleRelExpr->find_expr_references_walker.

This is a fix for commit f80bedd52, "Allow ALTER COLUMN SET EXPRESSION
on virtual columns with CHECK constraints".

Author: jian he <jian(dot)universality(at)gmail(dot)com>
Co-authored-by: Peter Eisentraut <peter(at)eisentraut(dot)org>
Reported-by: Ayush Tiwari <ayushtiwari(dot)slg01(at)gmail(dot)com>
Reviewed-by: Ayush Tiwari <ayushtiwari(dot)slg01(at)gmail(dot)com>
Reviewed-by: solai v <solai(dot)cdac(at)gmail(dot)com>
Reviewed-by: Zsolt Parragi <zsolt(dot)parragi(at)percona(dot)com>
Discussion: https://www.postgresql.org/message-id/flat/CAJTYsWXOkyeDVbzymWc9sKrq7Y_MUv6XJXN4H9GfsBOPd3NJ+w(at)mail(dot)gmail(dot)com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a4639d64e2199885f8e995395b6fe874cb7228bf

Modified Files
--------------
src/backend/commands/tablecmds.c | 176 ++++++++++++++++++++++++
src/test/regress/expected/generated_stored.out | 9 ++
src/test/regress/expected/generated_virtual.out | 9 ++
src/test/regress/sql/generated_stored.sql | 10 ++
src/test/regress/sql/generated_virtual.sql | 10 ++
5 files changed, 214 insertions(+)