can uncommited update influence the performance of select???

From: <zhangguoping_at_boco.com.cn>
Date: Fri, 28 Mar 2003 21:57:59 +0800
Message-ID: <b61k7t$1k2i$1@mail.cn99.com>

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The next example illustrates the read consistency trap. Without knowing that an
uncommitted transaction had made a series of updates to the NAME column it is
very difficult to see why so many block visits would be incurred.

Cases like this are not normally repeatable: if the process were run again, it is
unlikely that another transaction would interact with it in the same way. SELECT name_id
FROM cq_names
WHERE name = ¡¯FLOOR¡¯;
call count cpu elapsed disk query current rows ---- ----- --- ------- ---- ----- ------- ----

Parse 1    0.10   0.18     0     0      0   0
Execute 1  0.00   0.00     0     0      0   0
Fetch 1    0.11   0.21     2   101      0   1


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how to explain the example??

thks Received on Fri Mar 28 2003 - 07:57:59 CST