[HACKERS] Reusing Dead Tuples:

[Janardhan]

Hi,
I am doing some experiments on dead tuples, I am looking of reusing the
dead tuples apace in a particular page during the "Update".This patch is meant for the tables
which are heavily updated to avoid vacuum very frequently.By using it will arrest the size of
table for heavily updated table. The algorithm works like this:
1) During the update it check for the dead tuples in the current page(page that contain
the tuple that need to be updated). If it finds any dead tuples it uses the dead tuple space
by ovewriting on dead tuple. The checking of dead tuple is very similer to the task that of
lazy vaccum.
2) If it cannot find any dead tuple it proceed as usual by inserting at the end of table .

Performance Effect:
1) The CPU processing will be slighly more for the update, but io processing is
exactly same
2) The size of table grows slower under heavy update , so vacuum is not required very frequently.
The total processing for update is more or less same even after doing large number of updates without vacuum.

Does it breaks anythings by overwriting the dead tuples ?.

Comments?.

jana



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