<?xml version="1.0" encoding="UTF-8"?><rss version="2.0"
	xmlns:content="http://purl.org/rss/1.0/modules/content/"
	xmlns:dc="http://purl.org/dc/elements/1.1/"
	xmlns:atom="http://www.w3.org/2005/Atom"
	xmlns:sy="http://purl.org/rss/1.0/modules/syndication/"
	xmlns:georss="http://www.georss.org/georss" xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#" xmlns:media="http://search.yahoo.com/mrss/"
		>
<channel>
	<title>Comments on: Distributed Queries</title>
	<atom:link href="http://jonathanlewis.wordpress.com/2009/07/01/distributed-queries/feed/" rel="self" type="application/rss+xml" />
	<link>http://jonathanlewis.wordpress.com/2009/07/01/distributed-queries/</link>
	<description>Just another Oracle weblog</description>
	<lastBuildDate>Fri, 24 May 2013 13:27:07 +0000</lastBuildDate>
	<sy:updatePeriod>hourly</sy:updatePeriod>
	<sy:updateFrequency>1</sy:updateFrequency>
	<generator>http://wordpress.com/</generator>
	<item>
		<title>By: Ignoring Hints &#171; Oracle Scratchpad</title>
		<link>http://jonathanlewis.wordpress.com/2009/07/01/distributed-queries/#comment-36274</link>
		<dc:creator><![CDATA[Ignoring Hints &#171; Oracle Scratchpad]]></dc:creator>
		<pubDate>Wed, 19 May 2010 21:05:51 +0000</pubDate>
		<guid isPermaLink="false">http://jonathanlewis.wordpress.com/?p=1672#comment-36274</guid>
		<description><![CDATA[[...] Lewis @ 9:04 pm UTC May 19,2010   I&#8217;ve previously published a couple of notes (here and here) about the driving_site() hint. The first note pointed out that the hint was deliberately ignored [...]]]></description>
		<content:encoded><![CDATA[<p>[...] Lewis @ 9:04 pm UTC May 19,2010   I&#8217;ve previously published a couple of notes (here and here) about the driving_site() hint. The first note pointed out that the hint was deliberately ignored [...]</p>
]]></content:encoded>
	</item>
	<item>
		<title>By: Jonathan Lewis</title>
		<link>http://jonathanlewis.wordpress.com/2009/07/01/distributed-queries/#comment-34207</link>
		<dc:creator><![CDATA[Jonathan Lewis]]></dc:creator>
		<pubDate>Sun, 23 Aug 2009 08:32:54 +0000</pubDate>
		<guid isPermaLink="false">http://jonathanlewis.wordpress.com/?p=1672#comment-34207</guid>
		<description><![CDATA[&gt;&gt; the remote database is sending us just the result 
&gt;&gt; It “gets” the rows from dist_home

Just trying to remove all ambiguity:
&quot;dist_home&quot;, &quot;me&quot; and &quot;us&quot; are at the local database.
The remote database &quot;gets&quot; the rows from dist_home &lt;i&gt;[us/me]&lt;/i&gt; by sending us &lt;i&gt;[dist_home/me]&lt;/i&gt; a select statement that asks for some rows each time it gets a row from dist_away.]]></description>
		<content:encoded><![CDATA[<p>&gt;&gt; the remote database is sending us just the result<br />
&gt;&gt; It “gets” the rows from dist_home</p>
<p>Just trying to remove all ambiguity:<br />
&#8220;dist_home&#8221;, &#8220;me&#8221; and &#8220;us&#8221; are at the local database.<br />
The remote database &#8220;gets&#8221; the rows from dist_home <i>[us/me]</i> by sending us <i>[dist_home/me]</i> a select statement that asks for some rows each time it gets a row from dist_away.</p>
]]></content:encoded>
	</item>
	<item>
		<title>By: todorbotev</title>
		<link>http://jonathanlewis.wordpress.com/2009/07/01/distributed-queries/#comment-34202</link>
		<dc:creator><![CDATA[todorbotev]]></dc:creator>
		<pubDate>Sat, 22 Aug 2009 13:56:13 +0000</pubDate>
		<guid isPermaLink="false">http://jonathanlewis.wordpress.com/?p=1672#comment-34202</guid>
		<description><![CDATA[&gt; the remote database is running the query, and sending a select statement to me for each row it selects from dist_away.

My impression is that the remote database is sending us just the result in order to display it. It &quot;gets&quot; the rows from dist_home, performs the inner loop on-site and sends us the reult back.]]></description>
		<content:encoded><![CDATA[<p>&gt; the remote database is running the query, and sending a select statement to me for each row it selects from dist_away.</p>
<p>My impression is that the remote database is sending us just the result in order to display it. It &#8220;gets&#8221; the rows from dist_home, performs the inner loop on-site and sends us the reult back.</p>
]]></content:encoded>
	</item>
	<item>
		<title>By: Wolfgang</title>
		<link>http://jonathanlewis.wordpress.com/2009/07/01/distributed-queries/#comment-33789</link>
		<dc:creator><![CDATA[Wolfgang]]></dc:creator>
		<pubDate>Sun, 05 Jul 2009 11:09:45 +0000</pubDate>
		<guid isPermaLink="false">http://jonathanlewis.wordpress.com/?p=1672#comment-33789</guid>
		<description><![CDATA[Jonathan,

I&#039;m thinking about a kind of dynamic sampling parameter for remote queries. Lets call it remote_stats. If remote_stats is set to 1 only basic informations are retrieved from the remote instance (you already mentioned them) and as you set remote_stats to a higher value more and more information about the remote tables are requested from the other instance.
So the user can decide what&#039;s more important: less network overhead or more round trips and probably a better execution plan.]]></description>
		<content:encoded><![CDATA[<p>Jonathan,</p>
<p>I&#8217;m thinking about a kind of dynamic sampling parameter for remote queries. Lets call it remote_stats. If remote_stats is set to 1 only basic informations are retrieved from the remote instance (you already mentioned them) and as you set remote_stats to a higher value more and more information about the remote tables are requested from the other instance.<br />
So the user can decide what&#8217;s more important: less network overhead or more round trips and probably a better execution plan.</p>
]]></content:encoded>
	</item>
	<item>
		<title>By: Jonathan Lewis</title>
		<link>http://jonathanlewis.wordpress.com/2009/07/01/distributed-queries/#comment-33787</link>
		<dc:creator><![CDATA[Jonathan Lewis]]></dc:creator>
		<pubDate>Sun, 05 Jul 2009 07:33:40 +0000</pubDate>
		<guid isPermaLink="false">http://jonathanlewis.wordpress.com/?p=1672#comment-33787</guid>
		<description><![CDATA[Wolfgang,

Can you be more precise in which bit of information you are thinking of ?

The local database will request basic object statistics from the remote database (table stats, index stats, simple column stats) before optimising the query; but there are two &quot;flaws&quot; to the strategy:

a) It doesn&#039;t request histogram data from the remote database

b) When doing the optimizer calculation it doesn&#039;t allow any extra costs for round-trip time to the remote database. It simply uses the statistics as if the tables were all local tables.]]></description>
		<content:encoded><![CDATA[<p>Wolfgang,</p>
<p>Can you be more precise in which bit of information you are thinking of ?</p>
<p>The local database will request basic object statistics from the remote database (table stats, index stats, simple column stats) before optimising the query; but there are two &#8220;flaws&#8221; to the strategy:</p>
<p>a) It doesn&#8217;t request histogram data from the remote database</p>
<p>b) When doing the optimizer calculation it doesn&#8217;t allow any extra costs for round-trip time to the remote database. It simply uses the statistics as if the tables were all local tables.</p>
]]></content:encoded>
	</item>
	<item>
		<title>By: Wolfgang</title>
		<link>http://jonathanlewis.wordpress.com/2009/07/01/distributed-queries/#comment-33784</link>
		<dc:creator><![CDATA[Wolfgang]]></dc:creator>
		<pubDate>Sun, 05 Jul 2009 05:36:46 +0000</pubDate>
		<guid isPermaLink="false">http://jonathanlewis.wordpress.com/?p=1672#comment-33784</guid>
		<description><![CDATA[I wonder why Oracle does not simply query the remote data dictionary (or ask the remote CBO) to get the needed information.]]></description>
		<content:encoded><![CDATA[<p>I wonder why Oracle does not simply query the remote data dictionary (or ask the remote CBO) to get the needed information.</p>
]]></content:encoded>
	</item>
	<item>
		<title>By: Blogroll Report 26/06/2009 – 03/07/2006 &#171; Coskan&#8217;s Approach to Oracle</title>
		<link>http://jonathanlewis.wordpress.com/2009/07/01/distributed-queries/#comment-33774</link>
		<dc:creator><![CDATA[Blogroll Report 26/06/2009 – 03/07/2006 &#171; Coskan&#8217;s Approach to Oracle]]></dc:creator>
		<pubDate>Fri, 03 Jul 2009 15:29:40 +0000</pubDate>
		<guid isPermaLink="false">http://jonathanlewis.wordpress.com/?p=1672#comment-33774</guid>
		<description><![CDATA[[...] Jonathan Lewis -Distributed Queries [...]]]></description>
		<content:encoded><![CDATA[<p>[...] Jonathan Lewis -Distributed Queries [...]</p>
]]></content:encoded>
	</item>
	<item>
		<title>By: Colin 't Hart</title>
		<link>http://jonathanlewis.wordpress.com/2009/07/01/distributed-queries/#comment-33739</link>
		<dc:creator><![CDATA[Colin 't Hart]]></dc:creator>
		<pubDate>Wed, 01 Jul 2009 10:51:58 +0000</pubDate>
		<guid isPermaLink="false">http://jonathanlewis.wordpress.com/?p=1672#comment-33739</guid>
		<description><![CDATA[Info on connection qualifier is here: http://download.oracle.com/docs/cd/B28359_01/server.111/b28310/ds_admin002.htm#i1008068]]></description>
		<content:encoded><![CDATA[<p>Info on connection qualifier is here: <a href="http://download.oracle.com/docs/cd/B28359_01/server.111/b28310/ds_admin002.htm#i1008068" rel="nofollow">http://download.oracle.com/docs/cd/B28359_01/server.111/b28310/ds_admin002.htm#i1008068</a></p>
]]></content:encoded>
	</item>
	<item>
		<title>By: Distributed DML &#171; Oracle Scratchpad</title>
		<link>http://jonathanlewis.wordpress.com/2009/07/01/distributed-queries/#comment-33734</link>
		<dc:creator><![CDATA[Distributed DML &#171; Oracle Scratchpad]]></dc:creator>
		<pubDate>Wed, 01 Jul 2009 07:21:54 +0000</pubDate>
		<guid isPermaLink="false">http://jonathanlewis.wordpress.com/?p=1672#comment-33734</guid>
		<description><![CDATA[[...] [Further reading: Distributed Queries]    Comments (11) [...]]]></description>
		<content:encoded><![CDATA[<p>[...] [Further reading: Distributed Queries]    Comments (11) [...]</p>
]]></content:encoded>
	</item>
</channel>
</rss>
