Hi, I'd like to propose to change pg_controldata so that it reports the name of WAL file containing the latest checkpoint's REDO record, as follows:
$ pg_controldata $PGDATA ... Latest checkpoint's REDO location: 0/16D6ACC (file 000000010000000000000001) Latest checkpoint's TimeLineID: 1 ... This simplifies very much the way to calculate the archive file cutoff point because the reported WAL file is just cutoff point itself. If the file name is not reported, we have to calculate the cutoff point from the reported location and timeline, which is complicated calculation. We can use pg_xlogfile_name function to calculate that, but it cannot be executed in the standby. Another problem is that pg_xlogfile_name always uses current timeline for the calculation, so if the reported timeline is not the same as current one, pg_xlogfile_name cannot return the correct WAL file name. Making pg_controldata report that WAL file name gets rid of such a complexity. You may think that archive_cleanup_command is usable for that purpose. That's true. But it's not usable simply for the case where there are more than one standby servers. In this case, the archive file cutoff point needs to be calculated from each standby's REDO location and timeline. Attached patch changes pg_controldata as above. Thought? Regards, -- Fujii Masao NIPPON TELEGRAPH AND TELEPHONE CORPORATION NTT Open Source Software Center
*** a/src/bin/pg_controldata/pg_controldata.c --- b/src/bin/pg_controldata/pg_controldata.c *************** *** 24,29 **** --- 24,30 ---- #include <fcntl.h> #include "access/xlog.h" + #include "access/xlog_internal.h" #include "catalog/pg_control.h" *************** *** 101,106 **** main(int argc, char *argv[]) --- 102,110 ---- char sysident_str[32]; const char *strftime_fmt = "%c"; const char *progname; + uint32 log; + uint32 seg; + char xlogfilename[MAXFNAMELEN]; set_pglocale_pgservice(argv[0], PG_TEXTDOMAIN("pg_controldata")); *************** *** 177,182 **** main(int argc, char *argv[]) --- 181,193 ---- localtime(&time_tmp)); /* + * Calculate the WAL file name containing the latest checkpoint's REDO + * record. + */ + XLByteToSeg(ControlFile.checkPointCopy.redo, log, seg); + XLogFileName(xlogfilename, ControlFile.checkPointCopy.ThisTimeLineID, log, seg); + + /* * Format system_identifier separately to keep platform-dependent format * code out of the translatable message string. */ *************** *** 204,212 **** main(int argc, char *argv[]) printf(_("Prior checkpoint location: %X/%X\n"), ControlFile.prevCheckPoint.xlogid, ControlFile.prevCheckPoint.xrecoff); ! printf(_("Latest checkpoint's REDO location: %X/%X\n"), ControlFile.checkPointCopy.redo.xlogid, ! ControlFile.checkPointCopy.redo.xrecoff); printf(_("Latest checkpoint's TimeLineID: %u\n"), ControlFile.checkPointCopy.ThisTimeLineID); printf(_("Latest checkpoint's full_page_writes: %s\n"), --- 215,224 ---- printf(_("Prior checkpoint location: %X/%X\n"), ControlFile.prevCheckPoint.xlogid, ControlFile.prevCheckPoint.xrecoff); ! printf(_("Latest checkpoint's REDO location: %X/%X (file %s)\n"), ControlFile.checkPointCopy.redo.xlogid, ! ControlFile.checkPointCopy.redo.xrecoff, ! xlogfilename); printf(_("Latest checkpoint's TimeLineID: %u\n"), ControlFile.checkPointCopy.ThisTimeLineID); printf(_("Latest checkpoint's full_page_writes: %s\n"),
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