Re: [HACKERS] PQfnumber and quoted identifiers - Mailing list pgsql-interfaces
From | Tom Lane |
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Subject | Re: [HACKERS] PQfnumber and quoted identifiers |
Date | |
Msg-id | 1258.1065373207@sss.pgh.pa.us Whole thread Raw |
Responses |
Re: [HACKERS] PQfnumber and quoted identifiers
(Andreas Pflug <pgadmin@pse-consulting.de>)
|
List | pgsql-interfaces |
[ pgsql-interfaces added to cc list ] Andreas Pflug <pgadmin@pse-consulting.de> writes: > Peter Eisentraut wrote: >> There was a discussion on -interfaces that might need more consideration. >> >> http://archives.postgresql.org/pgsql-interfaces/2003-09/msg00026.php >> >> Apparently, it has so far been an undocumented feature of libpq's function >> PGfnumber (return column number from column name) that the column name >> needs to be double-quoted if it contains upper-case letters. That, is you >> need to write >> >> PQfnumber(res, "\"Bar\"") >> >> I think this is completely bizarre and pointless. This is a C interface >> and not SQL. Other libpq functions that accept names of SQL objects don't >> do this. Also, PQfname and PQfnumber ought to be inverses. >> >> Since this behavior was undocumented and no one had noticed it in the last >> 10 years, I think we can away with removing it. > I don't agree; you'll certainly break all libpq apps that contact > databases with columns that have uppercase or special chars, and the > failure might be very subtle because in most cases you wouldn't expect > that this function call fails after you successfully created a rowset. That was pretty much the argument that carried the day in the earlier thread. However, I'm not sure how many people really use PQfnumber (as opposed to hard-wiring assumptions about returned column numbers), and it would seem that the intersection of those people with people who use mixed-case column names may be nearly the empty set. If a lot of people did this, the behavior would have been discussed and documented (or changed) long ago. So I'm not convinced that we'd really break very many apps by changing to the behavior that everyone seems to agree is more sensible. A data point is that we did make comparable changes to the handling of database names a couple releases ago, and we got few if any gripes. Another data point is that the original Berkeley coding of PQfnumber did not have the case folding/dequoting behavior. The history seems to be: Original code: straight strcmp() of argument against returned column name 1997-05-19 23:38: replace strcmp() with strcasecmp() (no dequoting logic, pretty obviously a broken idea in hindsight) 1997-11-10 00:10: attempted to implement the current behavior of dequoting+downcasing, but due to a typo, the actual effect was to revert the behavior to exact match 1999-02-03 15:19: fix typo, installing the current behavior So other than the shortlived 6.2 release, releases before 6.5 had the behavior Peter wants. I find it interesting that it took more than a year for anyone to notice that the putative dequoting+downcasing logic installed for 6.3 didn't work. regards, tom lane
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