Обсуждение: BUG #2905: min and max return incorrect text type
The following bug has been logged online: Bug reference: 2905 Logged by: Adriaan van Os Email address: postgres@microbizz.nl PostgreSQL version: 8.1.4 Operating system: Mac OS X 10.4.6, intel Description: min and max return incorrect text type Details: Table 9-37. Aggregate Functions in the Postgres docs states that the return type for min and max is the "same as argument type". However, min(VARCHAROID) and max(VARCHAROID) return TEXTOID as a result type.
Adriaan van Os wrote: > > The following bug has been logged online: > > Bug reference: 2905 > Logged by: Adriaan van Os > Email address: postgres@microbizz.nl > PostgreSQL version: 8.1.4 > Operating system: Mac OS X 10.4.6, intel > Description: min and max return incorrect text type > Details: > > Table 9-37. Aggregate Functions in the Postgres docs states that the return > type for min and max is the "same as argument type". > > However, min(VARCHAROID) and max(VARCHAROID) return TEXTOID as a result > type. Yea, they are internally treated as very similar types. -- Bruce Momjian bruce@momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +
Bruce Momjian wrote: > Adriaan van Os wrote: >> The following bug has been logged online: >> >> Bug reference: 2905 >> Logged by: Adriaan van Os >> Email address: postgres@microbizz.nl >> PostgreSQL version: 8.1.4 >> Operating system: Mac OS X 10.4.6, intel >> Description: min and max return incorrect text type >> Details: >> >> Table 9-37. Aggregate Functions in the Postgres docs states that the return >> type for min and max is the "same as argument type". >> >> However, min(VARCHAROID) and max(VARCHAROID) return TEXTOID as a result >> type. > > Yea, they are internally treated as very similar types. But "internally treated as very similar" is still not "same as argument type". Computing requires exactness. Adriaan van OS
Adriaan van Os wrote: > >> However, min(VARCHAROID) and max(VARCHAROID) return TEXTOID as a > >> result type. > > > > Yea, they are internally treated as very similar types. > > But "internally treated as very similar" is still not "same as > argument type". Computing requires exactness. Aside from the apparent discrepancy between the documentation and the actual behavior, is there an actual use case where this is a problem? -- Peter Eisentraut http://developer.postgresql.org/~petere/
Peter Eisentraut wrote: > Adriaan van Os wrote: > > >> However, min(VARCHAROID) and max(VARCHAROID) return TEXTOID as a > > >> result type. > > > > > > Yea, they are internally treated as very similar types. > > > > But "internally treated as very similar" is still not "same as > > argument type". Computing requires exactness. > > Aside from the apparent discrepancy between the documentation and the > actual behavior, is there an actual use case where this is a problem? No, I don't think so, and I am reluctant to adjust the documentation to say "or similar". -- Bruce Momjian bruce@momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +
Bruce Momjian <bruce@momjian.us> writes:
> Peter Eisentraut wrote:
>> Aside from the apparent discrepancy between the documentation and the
>> actual behavior, is there an actual use case where this is a problem?
> No, I don't think so, and I am reluctant to adjust the documentation to
> say "or similar".
The documentation is correct as it stands: max(text) returns text.
Adriaan's complaint about max(varchar) is off base because there is
no such function.
regards, tom lane
Adriaan van Os wrote: > Besides, the question is absurd. I stumble over a stone on the road, > report it and then you ask "is there an actual use case where this is > a problem". Why else do I report it ? What you probably wanted to ask > is: "Apart from the missing warning along the road, couldn't you have > walked around that stone ?" No, I'm asking what kind of stone it was and why it is a problem. -- Peter Eisentraut http://developer.postgresql.org/~petere/
Peter Eisentraut wrote: > Adriaan van Os wrote: >>>> However, min(VARCHAROID) and max(VARCHAROID) return TEXTOID as a >>>> result type. >>> Yea, they are internally treated as very similar types. >> But "internally treated as very similar" is still not "same as >> argument type". Computing requires exactness. > > Aside from the apparent discrepancy between the documentation and the > actual behavior, is there an actual use case where this is a problem? Dijkstra's "Rule 0: Dont Make a Mess of It <http://www.cs.utexas.edu/users/EWD/> and the virtues of strong typing, which, for SQL, imply checks at runtime <http://en.wikipedia.org/wiki/Type_safety>. Besides, the question is absurd. I stumble over a stone on the road, report it and then you ask "is there an actual use case where this is a problem". Why else do I report it ? What you probably wanted to ask is: "Apart from the missing warning along the road, couldn't you have walked around that stone ?" Well, in answer to that last question, I could have, but that is the wrong approach to computing. Regards, Adriaan van Os
Tom Lane wrote: > Bruce Momjian <bruce@momjian.us> writes: >> Peter Eisentraut wrote: >>> Aside from the apparent discrepancy between the documentation and the >>> actual behavior, is there an actual use case where this is a problem? > >> No, I don't think so, and I am reluctant to adjust the documentation to >> say "or similar". > > The documentation is correct as it stands: max(text) returns text. > Adriaan's complaint about max(varchar) is off base because there is > no such function. No, the documentation says that the Argument Type of max and min can be "any array, numeric, string, or date/time type" and that the Return type is the "same as argument type". The functions min and max applied to a field of type varchar return a function result of type text. So, if a max(varchar) function is missing and the cause of the text result type is implicit type casting, then the fact that there is no max(varchar) function is exactly the bug. Adriaan van Os
Adriaan van Os wrote: > Tom Lane wrote: > >Bruce Momjian <bruce@momjian.us> writes: > >>Peter Eisentraut wrote: > >>>Aside from the apparent discrepancy between the documentation and the > >>>actual behavior, is there an actual use case where this is a problem? > > > >>No, I don't think so, and I am reluctant to adjust the documentation to > >>say "or similar". > > > >The documentation is correct as it stands: max(text) returns text. > >Adriaan's complaint about max(varchar) is off base because there is > >no such function. > > No, the documentation says that the Argument Type of max and min can be > "any array, numeric, string, or date/time type" and that the Return type is > the "same as argument type". The functions min and max applied to a field > of type varchar return a function result of type text. So, if a > max(varchar) function is missing and the cause of the text result type is > implicit type casting, then the fact that there is no max(varchar) function > is exactly the bug. Do you have a specific situation on which this causes a problem for you? I mean, are you asking because it really bugs you, or just for the sake of being pedantic? -- Alvaro Herrera Valdivia, Chile ICBM: S 39º 49' 18.1", W 73º 13' 56.4" Tulio: oh, para qué servirá este boton, Juan Carlos? Policarpo: No, aléjense, no toquen la consola! Juan Carlos: Lo apretaré una y otra vez.
Alvaro Herrera wrote: > Adriaan van Os wrote: > > Tom Lane wrote: > > >Bruce Momjian <bruce@momjian.us> writes: > > >>Peter Eisentraut wrote: > > >>>Aside from the apparent discrepancy between the documentation and the > > >>>actual behavior, is there an actual use case where this is a problem? > > > > > >>No, I don't think so, and I am reluctant to adjust the documentation to > > >>say "or similar". > > > > > >The documentation is correct as it stands: max(text) returns text. > > >Adriaan's complaint about max(varchar) is off base because there is > > >no such function. > > > > No, the documentation says that the Argument Type of max and min can be > > "any array, numeric, string, or date/time type" and that the Return type is > > the "same as argument type". The functions min and max applied to a field > > of type varchar return a function result of type text. So, if a > > max(varchar) function is missing and the cause of the text result type is > > implicit type casting, then the fact that there is no max(varchar) function > > is exactly the bug. > > Do you have a specific situation on which this causes a problem for you? > I mean, are you asking because it really bugs you, or just for the sake > of being pedantic? And what suggestion do you have for a change? How would you like the documentation wording changed? -- Bruce Momjian bruce@momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +