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From Satheesh Bandaram <sathe...@Sourcery.Org>
Subject Re: [PATCH](DERBY-573) Provide support for optimizer overrides in Derby
Date Fri, 09 Dec 2005 20:31:46 GMT
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I haven't yet reviewed the patch... I will be looking at it, hopefully,
today.<br>
<br>
Don't think throwing an Exception is acceptable... That basically means
soft-upgrade model is broken, from customer point of view, right?
Without metadata queries, their applications probably wouldn't work.
May be we could evolve another way to perform the queries in soft
upgrade mode. Could we have a 'getProcedures_10.1' type statements,
when needed? Hopefully these will not be needed anytime soon and even
if we do, hopefully for only a few of these.<br>
<br>
Satheesh<br>
<br>
Mamta Satoor wrote:
<blockquote
 cite="midd9619e4a0512082059q41a71e06s2e7180b18789cb01@mail.gmail.com"
 type="cite">
  <div>Hi Satheesh,</div>
  <div>&nbsp;</div>
  <div>Thanks for reviewing the patch.</div>
  <div>&nbsp;</div>
  <div>I think your concern is well founded. A new column in a system
table referenced by metadata.properties would cause a problem in soft
upgrade mode. I am not sure if we have run into this in the past and
how we handled it. One way would be in soft upgrade mode, we should
catch exceptions thrown by metadata.properties queries and nest it
inside a more generic exception which will say that the metadata query
may not be suitable to run in soft upgrade mode. I realize this is not
very graceful, just a thought from top of my head. Any other
suggestions from anyone?
  </div>
  <div>&nbsp;</div>
  <div>Mamta<br>
  <br>
&nbsp;</div>
  <div><span class="gmail_quote">On 12/8/05, <b
 class="gmail_sendername">Satheesh Bandaram</b> &lt;<a
 href="mailto:satheesh@sourcery.org">satheesh@sourcery.org</a>&gt;
wrote:</span>
  <blockquote class="gmail_quote"
 style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left:
1ex;">I
will review this change and hope to commit it, if everything looks<br>
good. Let me know if anyone else is also planning on review or already
    <br>
have review comments. Thanks for the good write up too and researching<br>
soft/hard upgrades.<br>
    <br>
I have one question about the following... What happens if 10.2<br>
metadata.properties change in a way that is not compatible with a 10.1<br>
database? For example, I may have to add a column to SYSALIAS system<br>
table. If I use this column (I may not actually need to) in 10.2<br>
metadata.properties, wouldn't that cause problem with soft upgrade and<br>
10.1 database?<br>
    <br>
Satheesh<br>
    <br>
Mamta Satoor wrote:<br>
    <br>
&gt; Following is a brief description of upgrade code<br>
&gt; 1)If a 10.1 db is getting run in soft upgrade mode with 10.2, the<br>
&gt; system tables would still have the old 10.1 optimizer overrides
syntax<br>
&gt; which is not recognized by 10.2 The system tables of the 10.1 db
can't<br>
&gt; be modified in soft upgrade mode to store the new 10.2 optimizer<br>
&gt; overrides syntax for metadata queries because in soft upgrade,
system
    <br>
&gt; tables can't be modified in a backward incompatible way. To get
around<br>
&gt; this, I have changed the code in EmbedDatabaseMetaData.java to see
if<br>
&gt; db is getting run in soft upgrade mode. If yes, then it should
read
    <br>
&gt; the metadata queries from metadata.properties rather than system<br>
&gt; tables. This will work because metadata.properties for 10.2 release<br>
&gt; has been modified to use the new optimizer overrides syntax.<br>
&gt;<br>
    <br>
  </blockquote>
  </div>
  <br>
</blockquote>
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