some questions in postgresql developping

<div class="Section1"><p align="left" class="MsoNormal" style="text-align:left"><span lang="EN-US"> </span><p
class="MsoNormal"><spanlang="EN-US">Hello,</span><p class="MsoNormal"><span lang="EN-US">I’m a student from Nankai
Universityin China. Now I and my team do a project which aims to integrate XML to Postgresql. What I do is to complete
thefunction of XML Update.</span><p class="MsoNormal"><span lang="EN-US">Now I’m researching in concurrency control. I
haveread the code about the concurrency control for a long time and I’m confident that I know it much. But I am puzzled
thatwhy we need to lock tuple. I think locking transaction is sufficient. I don’t think the tuple lock is good at
improvingexecuting rate or anything.</span><p class="MsoNormal"><span lang="EN-US">I am wishing for your
reply.</span><pclass="MsoNormal"><span lang="EN-US"> </span><p class="MsoNormal"><span lang="EN-US">Best
Regards,</span><pclass="MsoNormal"><span lang="EN-US"> </span><p class="MsoNormal"><span lang="EN-US">--Huang
Xiaocheng</span><pclass="MsoNormal"><span lang="EN-US">--Database & Information System Lab, Nankai University,
China</span><pclass="MsoNormal"><span lang="EN-US"> </span></div><br /><br />__________ Information from ESET NOD32
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