Request: Posgresql ALTER COLUMN syntax support

[SkaceKamen]

Support for ALTER TABLE "table" ALTER COLUMN "column" (operation) would be nice. Looking a the current docs (https://www.postgresql.org/docs/current/sql-altertable.html) following operations are available:

ALTER [ COLUMN ] column_name [ SET DATA ] TYPE data_type [ COLLATE collation ] [ USING expression ]
ALTER [ COLUMN ] column_name SET DEFAULT expression
ALTER [ COLUMN ] column_name DROP DEFAULT
ALTER [ COLUMN ] column_name { SET | DROP } NOT NULL
ALTER [ COLUMN ] column_name DROP EXPRESSION [ IF EXISTS ]
ALTER [ COLUMN ] column_name ADD GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( sequence_options ) ]
ALTER [ COLUMN ] column_name { SET GENERATED { ALWAYS | BY DEFAULT } | SET sequence_option | RESTART [ [ WITH ] restart ] } [...]
ALTER [ COLUMN ] column_name DROP IDENTITY [ IF EXISTS ]
ALTER [ COLUMN ] column_name SET STATISTICS integer
ALTER [ COLUMN ] column_name SET ( attribute_option = value [, ... ] )
ALTER [ COLUMN ] column_name RESET ( attribute_option [, ... ] )
ALTER [ COLUMN ] column_name SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN | DEFAULT }
ALTER [ COLUMN ] column_name SET COMPRESSION compression_method

Some of those seem to be pretty niche, but IMO those are pretty common:

ALTER [ COLUMN ] column_name [ SET DATA ] TYPE data_type [ COLLATE collation ] [ USING expression ]
ALTER [ COLUMN ] column_name SET DEFAULT expression
ALTER [ COLUMN ] column_name DROP DEFAULT
ALTER [ COLUMN ] column_name { SET | DROP } NOT NULL

Database Engine PostgreSQL

I'll attempt to implement the support myself, but I'm a bit confused how SQL stringifying works in the lib. Some rough pointers how to start would be nice :)

[taozhi8833998]

PostgresQL Alter Table Doc

[taozhi8833998]

@SkaceKamen The 'alter table' commonly used command is now supported.