<html><head></head><body>Hi Tom,<br>
<br>
<br>
<blockquote type="cite" cite="mid:4501(dot)987180015(at)sss(dot)pgh(dot)pa(dot)us"><pre wrap="">"Brian J. France" <a class="moz-txt-link-rfc2396E" href="mailto:postgresql(at)firehawksystems(dot)com"><postgresql(at)firehawksystems(dot)com></a> writes:<br></pre>
<blockquote type="cite"><pre wrap=""> I am getting a few of these errors in my web logs and didn't know what I could do to stop it.<br></pre></blockquote>
<blockquote type="cite"><pre wrap="">NOTICE: Deadlock detected -- See the lock(l) manual page for a possible cause.<br></pre></blockquote>
<blockquote type="cite"><pre wrap="">Error in query "UPDATE <table> SET <field> = <value> WHERE <field2> = <value2>" : ERROR: WaitOnLock: error on wakeup - Aborting this transaction<br></pre></blockquote>
<blockquote type="cite"><pre wrap="">Is this due to the hash index on field2 or due to the has index in general?<br></pre></blockquote>
<pre wrap=""><!----><br>Don't use hash indexes for concurrent applications. I don't really know<br>of any reason for preferring a hash index over a btree index in any case.<br><br> regards, tom lane<br></pre>
</blockquote>
Could you expand a little on the subject of Hash Vs BTree indexes? And in
particular "Don't use hash indexes for concurrent applications".<br>
I posted a question about deadlocks a week or two ago and I was advised to upgrade to 7.0.3 (from 7.0.2).
I did, but I still get a few deadlocks (i.e. all the backends eventually remain locked in requests).
<br>
I am using a lot of Hash indexes because they usually provide faster access
to a specific record than binary trees (O Vs OlogN). Most of my requests
simply lookup a record based on some specific account or transaction ID.
<br>
If using BTree instead of Hash indexes does not affect performance and solves my deadlock problem, please let me know!<br>
<br>
Thanks.<br>
<br>
--Maurice<br>
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