Hi!
I have a questions about setting transaction's wraparound limits. Function
SetTransactionIdLimit() in access/transam/varsup.c:
1)
xidWrapLimit = oldest_datfrozenxid + (MaxTransactionId >> 1);
if (xidWrapLimit < FirstNormalTransactionId)
xidWrapLimit += FirstNormalTransactionId;
Isn't it a problem if oldest_datfrozenxid > MaxTransactionId/2?
2)
xidStopLimit = xidWrapLimit - 1000000;
if (xidStopLimit < FirstNormalTransactionId)
xidStopLimit -= FirstNormalTransactionId;
xidWarnLimit = xidStopLimit - 10000000;
if (xidWarnLimit < FirstNormalTransactionId)
xidWarnLimit -= FirstNormalTransactionId;
Why does it use '-' instead of '+' if variable < FirstNormalTransactionId? In
this case it is easy to get xidStopLimit > xidWrapLimit or xidWarnLimit >
xidStopLimit...
Thank you.
--
Teodor Sigaev E-mail: [email protected]
WWW: http://www.sigaev.ru/
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