Hello, On 2020-Sep-28, Wang, Shenhao wrote:
> I have a problem about XLogReader callback system > > In xlog.c, function StartupXLOG > > xlogreader = > XLogReaderAllocate(wal_segment_size, NULL, > XL_ROUTINE(.page_read = > &XLogPageRead, > > .segment_open = NULL, > > .segment_close = wal_segment_close), > &private); > > XLogPageReader uses readFile to store the fd, and I can't find any > location to set the value of seg.ws_file. Hmm, AFAICS (admittedly a quick look) you're right: because XLogPageRead does not touch ws_file, wal_segment_close would always find that it's unset (-1) so XLogReaderFree would have nothing to do. The whole XLogReader abstraction remains pretty leaky, I'm afraid :-( Ideally we would plug those holes. Perhaps getting rid of readFile completely would be a solution, but I haven't analyzed it. > Is it necessary to set a segment_close callback? For this case it seems useless but not actually harmful. Have you come across some scenario in which it causes a problem? -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
