<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;"><p>>> 4. Won't it effect if we
don'tupdate xmin everytime and just noting the committed XIDs. The reason I am asking is that it is used in
tuple visibilitycheck so with new idea in some cases instead of just returning >> from begining by checking
xminit has to go through the committed XID list. <p>>> I understand that there may be less cases or the
improvementby your idea can supesede this minimal effect. However some cases can be defeated.<br /><br /> >The
snapshotxmin has to be up to date. I'm not planning to break that because it would be wrong.<p> In the approach
mentionedin your idea, it mentioned that once after taking snapshot, only committed XIDs will be updated and sometimes
snapshotitself.<p> So when the xmin will be updated according to your idea.<br /><br /> >RecentGlobalXmin doesn't
needto be completely up to date, and in fact recomputing it on every snapshot becomes prohibitively expensive with this
approach. I'm still struggling with the best way to handle that.<p> RecentGlobalXmin and RecentXmin are mostly
updatedwith snapshots xmin and that too outside ProcArrayLock, so why it will be expensive if you have updated xmin.<br
/><br/><p>With Regards,<p>Amit Kapila.<p><br />
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