Postgres動態更新約束外鍵

Question

我有很多帶有許多外鍵的表，並且它們幾乎都是UPDATE NO ACTION和DELETE NO ACTION。

是否可以將所有這些外鍵動態更新為CASCADE，而不是NO ACTION或RESTRICT？

例如：

ALTER TABLE * ALTER FOREIGN KEY * SET ON UPDATE CASCADE ON DELETE CASCADE;

你的，Diogo

Answer 1

不，這是不可能的。

您將需要刪除並重新創建所有約束，因為不能像這樣更改外鍵約束。

以下語句將生成必要的alter table語句，以刪除並重新創建外鍵：

select 'alter table '||pgn.nspname||'.'||tbl.relname||' drop constraint '||cons.conname||';'
from pg_constraint cons
  join pg_class tbl on cons.confrelid = tbl.oid
  join pg_namespace pgn on pgn.oid = tbl.relnamespace
where contype = 'f'

union all 

select 'alter table '||pgn.nspname||'.'||tbl.relname||' add constraint '||cons.conname||' '||pg_get_constraintdef(cons.oid, true)||' ON UPDATE CASCADE ON DELETE CASCADE;'
from pg_constraint cons
  join pg_class tbl on cons.confrelid = tbl.oid
  join pg_namespace pgn on pgn.oid = tbl.relnamespace
where contype = 'f'

將此語句的輸出保存到文件中並運行它。

確保在運行生成的語句之前對其進行驗證！

Answer 2

我將使用以下代碼來生成必要的alter table SQL語句，以刪除並重新創建外鍵（按順序）：

    select 'ALTER TABLE '||pgn.nspname||'.'||tbl.relname||' DROP CONSTRAINT '||cons.conname||';' as sqlstr
    from pg_constraint cons
      join pg_class tbl on cons.conrelid = tbl.oid
      join pg_namespace pgn on pgn.oid = tbl.relnamespace
    where contype = 'f' 
    union
    select 'ALTER TABLE '||pgn.nspname||'.'||tbl.relname||' ADD CONSTRAINT '||cons.conname||' FOREIGN KEY ('||(select attname from pg_attribute where attrelid=cons.conrelid and attnum = ANY(cons.conkey))||') REFERENCES '||tblf.relname||' ('||(select attname from pg_attribute where attrelid=cons.confrelid and attnum = ANY(cons.confkey))||')  ON UPDATE CASCADE ON DELETE CASCADE;'  as sqlstr
    from pg_constraint cons
      join pg_class tbl on cons.conrelid = tbl.oid
      join pg_namespace pgn on pgn.oid = tbl.relnamespace
      join pg_class tblf on cons.confrelid = tblf.oid
    where contype = 'f' 

    ORDER BY sqlstr desc