| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Christopher Kings-Lynne" <chriskl(at)familyhealth(dot)com(dot)au> |
| Cc: | "Andreas Pflug" <Andreas(dot)Pflug(at)web(dot)de>, "Alvaro Herrera" <alvherre(at)dcc(dot)uchile(dot)cl>, "Hackers" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: pg_get_triggerdef in pg_dump |
| Date: | 2003-06-19 02:33:17 |
| Message-ID: | 5766.1055989997@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
"Christopher Kings-Lynne" <chriskl(at)familyhealth(dot)com(dot)au> writes:
>> There might be other cases of legal direct change of system catalog
>> entries, e,g. varchar to text, if they all are only names for internally
>> identical data structures. Can you tell which datatypes may be legally
>> interchanged?
> Yes, you can check if they're binary compatible from the pg_cast table....
But nearly all of the interesting cases require you to understand the
type's interpretation of typmod, and you can't learn that from a table.
How many cases are there where blindly looking for a binary-compatible
cast in pg_cast will really do you much good? AFAICS you'd have to set
atttypmod to -1 if you change atttypid without knowing very specifically
what you are changing from and to.
regards, tom lane
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