/*
* pg_switch_xlog: switch to next xlog file
*/
Datum
pg_switch_xlog(PG_FUNCTION_ARGS)
{
XLogRecPtr switchpoint;
char location[MAXFNAMELEN];
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
(errmsg("must be superuser to switch transaction log files"))));
if (RecoveryInProgress())
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("recovery is in progress"),
errhint("WAL control functions cannot be executed during recovery.")));
switchpoint = RequestXLogSwitch();
/*
* As a convenience, return the WAL location of the switch record
*/
snprintf(location, sizeof(location), "%X/%X",
switchpoint.xlogid, switchpoint.xrecoff);
PG_RETURN_TEXT_P(cstring_to_text(location));
}
/*
* CheckArchiveTimeout -- check for archive_timeout and switch xlog files
*
* This will switch to a new WAL file and force an archive file write if
* meaningful activity is recorded in the current WAL file. This includes most
* writes, including just a single checkpoint record, but excludes WAL records
* that were inserted with the XLOG_MARK_UNIMPORTANT flag being set (like
* snapshots of running transactions). Such records, depending on
* configuration, occur on regular intervals and don't contain important
* information. This avoids generating archives with a few unimportant
* records.
*/
static void
CheckArchiveTimeout(void)
{
pg_time_t now;
pg_time_t last_time;
XLogRecPtr last_switch_lsn;
if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
return;
now = (pg_time_t) time(NULL);
/* First we do a quick check using possibly-stale local state. */
if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
return;
/*
* Update local state ... note that last_xlog_switch_time is the last time
* a switch was performed *or requested*.
*/
last_time = GetLastSegSwitchData(&last_switch_lsn);
last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
/* Now we can do the real checks */
if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
{
/*
* Switch segment only when "important" WAL has been logged since the
* last segment switch (last_switch_lsn points to end of segment
* switch occurred in).
*/
if (GetLastImportantRecPtr() > last_switch_lsn)
{
XLogRecPtr switchpoint;
/* mark switch as unimportant, avoids triggering checkpoints */
switchpoint = RequestXLogSwitch(true);
/*
* If the returned pointer points exactly to a segment boundary,
* assume nothing happened.
*/
if ((switchpoint % XLogSegSize) != 0)
elog(DEBUG1, "write-ahead log switch forced (archive_timeout=%d)",
XLogArchiveTimeout);
}
/*
* Update state in any case, so we don't retry constantly when the
* system is idle.
*/
last_xlog_switch_time = now;
}
}
/*
* CheckArchiveTimeout -- check for archive_timeout and switch xlog files
*
* This will switch to a new WAL file and force an archive file write
* if any activity is recorded in the current WAL file, including just
* a single checkpoint record.
*/
static void
CheckArchiveTimeout(void)
{
pg_time_t now;
pg_time_t last_time;
if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
return;
now = (pg_time_t) time(NULL);
/* First we do a quick check using possibly-stale local state. */
if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
return;
/*
* Update local state ... note that last_xlog_switch_time is the last time
* a switch was performed *or requested*.
*/
last_time = GetLastSegSwitchTime();
last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
/* Now we can do the real check */
if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
{
XLogRecPtr switchpoint;
/* OK, it's time to switch */
switchpoint = RequestXLogSwitch();
/*
* If the returned pointer points exactly to a segment boundary,
* assume nothing happened.
*/
if ((switchpoint % XLogSegSize) != 0)
ereport(DEBUG1,
(errmsg("transaction log switch forced (archive_timeout=%d)",
XLogArchiveTimeout)));
/*
* Update state in any case, so we don't retry constantly when the
* system is idle.
*/
last_xlog_switch_time = now;
}
}
/*
* pg_switch_xlog: switch to next xlog file
*
* Permission checking for this function is managed through the normal
* GRANT system.
*/
Datum
pg_switch_xlog(PG_FUNCTION_ARGS)
{
XLogRecPtr switchpoint;
if (RecoveryInProgress())
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("recovery is in progress"),
errhint("WAL control functions cannot be executed during recovery.")));
switchpoint = RequestXLogSwitch();
/*
* As a convenience, return the WAL location of the switch record
*/
PG_RETURN_LSN(switchpoint);
}
