Обсуждение: Foreign key data type mismatches
I was just annoyed to find out that a foreign key doesn't check whether the referenced column has a sufficiently similar data type, it only checks whether an = operator exists. This masks schema design errors and typos. Should this be tightened up, for example using the castability characteristics between the two data types? -- Peter Eisentraut peter_e@gmx.net
Peter Eisentraut wrote: >I was just annoyed to find out that a foreign key doesn't check whether >the referenced column has a sufficiently similar data type, it only checks >whether an = operator exists. This masks schema design errors and typos. >Should this be tightened up, for example using the castability >characteristics between the two data types? > > Sounds like a good idea. IMHO normally only *equal* data types should be referenced in a good data model design, but there's probably the need for some relaxed check option too. Regards, Andreas
Andreas Pflug wrote: > Peter Eisentraut wrote: > > >I was just annoyed to find out that a foreign key doesn't check whether > >the referenced column has a sufficiently similar data type, it only checks > >whether an = operator exists. This masks schema design errors and typos. > >Should this be tightened up, for example using the castability > >characteristics between the two data types? > > > > > > Sounds like a good idea. IMHO normally only *equal* data types should be > referenced in a good data model design, but there's probably the need > for some relaxed check option too. Yes, we already talked about throwing a warning if the primary/foreign key data types are mismatched. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001+ If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania19073
On Mon, 1 Dec 2003, Peter Eisentraut wrote: > I was just annoyed to find out that a foreign key doesn't check whether > the referenced column has a sufficiently similar data type, it only checks > whether an = operator exists. This masks schema design errors and typos. > Should this be tightened up, for example using the castability > characteristics between the two data types? Maybe, but IIRC the spec only requires comparability between the types involved. Since we don't use the same rules as the spec for that, existance of equality comparison was treated as the closest match to the requirement at the time.