> -----Original Message----- > From: Robert Haas [mailto:robertmh...@gmail.com] > Sent: Saturday, October 03, 2015 5:44 AM > To: Kaigai Kouhei(海外 浩平) > Cc: Amit Kapila; Andres Freund; pgsql-hackers > Subject: ##freemail## Re: [HACKERS] CustomScan support on readfuncs.c > > On Tue, Sep 29, 2015 at 6:19 PM, Kouhei Kaigai <kai...@ak.jp.nec.com> wrote: > >> On Mon, Sep 28, 2015 at 8:31 PM, Kouhei Kaigai <kai...@ak.jp.nec.com> > >> wrote: > >> >> Instead of doing this: > >> >> > >> >> + /* Dump library and symbol name instead of raw pointer */ > >> >> appendStringInfoString(str, " :methods "); > >> >> - _outToken(str, node->methods->CustomName); > >> >> + _outToken(str, node->methods->methods_library_name); > >> >> + appendStringInfoChar(str, ' '); > >> >> + _outToken(str, node->methods->methods_symbol_name); > >> >> > >> >> Suppose we just make library_name and symbol_name fields in the node > >> >> itself, that are dumped and loaded like any others. > >> >> > >> >> Would that be better? > >> >> > >> > I have no preference here. > >> > > >> > Even if we dump library_name/symbol_name as if field in CustomScan, > >> > not CustomScanMethods, in a similar way, we cannot use WRITE_STRING_FIELD > >> > here, because its 'fldname' assumes these members are direct field of > >> > CustomScan. > >> > > >> > /* Write a character-string (possibly NULL) field */ > >> > #define WRITE_STRING_FIELD(fldname) \ > >> > (appendStringInfo(str, " :" CppAsString(fldname) " "), \ > >> > _outToken(str, node->fldname)) > >> > >> Well that's exactly what I was suggesting: making them a direct field > >> of CustomScan. > >> > > Let me confirm. Are you suggesting to have library_name/symbol_name > > in CustomScan, not CustomScanMethods? > > I prefer these fields are in CustomScanMethods because we don't need > > to setup them again once PG_init set up these symbols. CustomScan has > > to be created every time when it is chosen by planner. > > True. But that doesn't cost much. I'm not sure it's better, so if > you don't like it, don't worry about it. > Yep, I like library_name and symbol_name are in CustomScanMethods because the table of callbacks and its identifiers are not separable
> >> > One other question I have. Do we have a portable way to lookup > >> > a pair of library and symbol by address? > >> > Glibc has dladdr() functions that returns these information, > >> > however, manpage warned it is not defined by POSIX. > >> > If we would be able to have any portable way, it may make the > >> > interface simpler. > >> > >> Yes: load_external_function. > >> > > It looks up an address by a pair of library and symbol name.... > > What I'm looking for is a portable function that looks up a pair > > of library and symbol name by an address, like dladdr() of glibc. > > I don't know whether other *nix or windows have these infrastructure. > > No, that doesn't exist, and the chances of us trying add that > infrastructure for this feature are nil. > OK, probably, it is the only way to expect extension put correct values on the pair of library and symbol names. I try to check whether the current patch workable with this direction using my extension. Please wait for a few days. Thanks, -- NEC Business Creation Division / PG-Strom Project KaiGai Kohei <kai...@ak.jp.nec.com> -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
