Shane Ambler schreef:
ries van Twisk wrote:
On Nov 18, 2008, at 9:47 AM, Erwin Moller wrote:
Hi group,
Considering following (simplified) example:
<snip>
Suppose I want to delete a record in tblnr1.
Does Postgres has some command/procedure/function to list tables
that have FK constraints on that table (tblnr1)
The data you are looking for is stored in the system catalogs.
http://www.postgresql.org/docs/8.3/interactive/catalogs.html
You should be able to come up with some SELECT's to get what you want.
and lists also the tables that have a FK constraint on tables that
have a FK constraint on the first? etc.
So I would like some kind of FK 'walker'.
I want this because:
1) I hate DELETE CASCADE because I am chicken (So I use a script to
delete all related records in the right order in a transaction)
That isn't being chicken it is being silly (or is that just stubborn ;).
PostgreSQL is designed to delete related records that you tell it to
delete. Let it do what it is suppose to do.
Hi,
No, that is not the kind of chicken I was talking about. ;-)
My chicken is more along these lines:
I often have some tables to which everything is related (eg tblcourse
that contains everything belonging to a certain course).
I don't want to make a single simple mistake that if I accidentally
delete an entry there, I lose all underlying data via the CASCADE.
That is why I decided never to use CASCADE, and simply do it by myself.
No big deal except that I have to find out the related tables.
I rather have a FK constraint violation error than an empty DB.
Hence my question.
I am not afraid that Postgres will screw up somehow.
That actually NEVER happened in all the years I am using it. Try that
with MSSQL or MySQL. I love Postgres. ;-)
2) I have a lot of tables and am afraid I miss some. And I am also a
bit lazy .-)
If your lazy why do all this manual work when you can leave it
automated? It won't miss a related record after you tell it to cascade
delete. This is an old well tested feature that you can rely on.
I described above.
That probably all sounds more aggressive than it should. Not having a
strong dig at you but I do want to emphasise the fact that you
shouldn't waste your time doing manually what the software is designed
to do.
No problem at all.
I totally agree with you.
I only have this fear I screw up (not Postgresql) if I use CASCADE and
accidentally delete a 'high' record in the chain.
Regards,
Erwin Moller
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