I implement my own vfs analogous to the vfs like fopen, fclose, fseek, fwrite, fread and etc. When I iterate a sql statement up to millions records, the fwrite fail due to pos of fseek is beyond the eof position. I am wondering whether the pos sometimes beyond eof is normal. If it is normal, I can do some tricks to write beyond the eof position.
On 2017年8月19日週六 下午5:13 Clemens Ladisch <clem...@ladisch.de> wrote: > Jacky Lam wrote: > > I recently meet a case that the file position offset of a pager is beyond > > EOF position of db. > > <http://pubs.opengroup.org/onlinepubs/9699919799/functions/lseek.html> > says: > | The lseek() function shall allow the file offset to be set beyond the end > | of the existing data in the file. If data is later written at this point, > | subsequent reads of data in the gap shall return bytes with the value 0 > | until data is actually written into the gap. > | [...] > | Although lseek() may position the file offset beyond the end of the file, > | this function does not itself extend the size of the file. [...] the only > | function in POSIX.1-2008 that may directly extend the size of the file is > | write(), truncate(), and ftruncate() > | [...] > | An invalid file offset that would cause [EINVAL] to be returned may be > | both implementation-defined and device-dependent > > The sqlite3_file object does not have a concept of "current file position"; > the xRead/xWrite/xTruncate functions have explicit offset/size parameters. > > But the Unix VFS internally takes advantage of this behaviour and writes > only the last byte of a newly allocated page. > > > I would like to know if ... it is a bug makes from my OS > > What VFS are you using? > > > Regards, > Clemens > _______________________________________________ > sqlite-users mailing list > sqlite-users@mailinglists.sqlite.org > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users > _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
