From: | "Hiroshi Inoue" <Inoue(at)tpf(dot)co(dot)jp> |
---|---|
To: | "Thomas Lockhart" <lockhart(at)alumni(dot)caltech(dot)edu> |
Cc: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Constantin Teodorescu" <teo(at)flex(dot)ro>, "Bruce Momjian" <maillist(at)candle(dot)pha(dot)pa(dot)us>, "Hannu Krosing" <hannu(at)trust(dot)ee>, <pgsql-hackers(at)postgreSQL(dot)org> |
Subject: | RE: [HACKERS] Interesting behaviour ! |
Date: | 1999-07-16 00:55:32 |
Message-ID: | 000c01becf25$e8047b60$2801007e@cadzone.tpf.co.jp |
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Lists: | pgsql-hackers |
>
> > Each type has a typeinput(char * => type ) proc and a typeoutput(
> > type -> char *) proc.
> > Doesn't int2in(int4out()) convert int4 to int2 ?
> > However,typeinput proc causes elog(ERROR) in most cases if it
> > couldn't convert correctly.
>
> Conversion using an intermediate string is possible, but not the
> preferred technique.
>
Every type of PostgreSQL must have typeinput/typeoutput procs.
So this technique doesn't need new procs/operators any more.
Isn't it an advantage ?
> The "automatic type coersion" code, used earlier in the parser, uses
> the convention that any single-argument function taking the source
> type as input and with the same name as the target type can be used
> for type conversion. For example, the function int4(int2) would
> convert int2 to int4. There are now routines in the parser for
> choosing conversion strategies and for finding candidates, and these
> could be reused for similar purposes when trying to match index
> arguments.
>
It seems reasonable.
But I'm afraid that the defintion of new type requires many functions
of type conversion.
Regards.
Hiroshi Inoue
Inoue(at)tpf(dot)co(dot)jp
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