Explicit vs Implicit Conversion ... Oracle's Answer

From: Daniel Morgan <damorgan_at_x.washington.edu>
Date: Sat, 07 Aug 2004 16:40:38 -0700
Message-ID: <1091922077.329411@yasure>

Back in mid-July I posted a test of one of Oracle's demos http://download-west.oracle.com/docs/cd/B13789_01/appdev.101/b10807/12_tune.htm#LNPLS012 and asked questions about why implicit conversion seemed faster than not just explicit conversion but also, in one case, no conversion at all.

Jonathan Lewis gave a good answer that I have incorporated into my lecture at the U. But I have also received an answer from Oracle and want to share that with the group.

So here it is:

Thanks for your comments on the doc.

I'm the writer currently assigned to the PL/SQL User's guide. I checked the example you mentioned and found similar results against a pre-beta 10g R2 database. I asked development about this and was told that the new code generator in Oracle 10g and new optimizing compiler automatically optimize the code and eliminate the need for any manual optimization. I'm going to need to rewrite the Tuning chapter in light of this information, and the example in question will be eliminated or completely changed.

However, I'm also still puzzled why the "c := 25;" conversion had the best performance, so I need to follow up on that.

Eric

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Daniel Morgan
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Received on Sat Aug 07 2004 - 18:40:38 CDT