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POmysql big query performance improvement
 

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  1. POmysql big query performance improvement
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    <p>Anyone know how I can optimise this query? It works but it takes so long that it causes server timeouts when there's a heavy load.</p> <pre><code>$screenRestrict="clientID='1' AND screenID='1'"; $lastupdate="1318515710"; INSERT INTO allvisits (clientID, screenID, hitID, entryPageID, entryPageName, xentryTime, xexitTime, pagecount, minsonsite)( SELECT clientID, screenID, id AS hitID, pageID AS entryPageID, (SELECT name FROM pages WHERE id=entryPageID) AS entryPageName, (SELECT clicktime FROM clicks WHERE id = hitID AND isFirstClick=1 ) AS xentryTime, (SELECT MIN(clicktime) FROM clicks WHERE $screenRestrict AND isLastClick=1 AND clicktime &gt; xentryTime) AS xexitTime, (SELECT COUNT(*) FROM clicks WHERE $screenRestrict AND clicktime BETWEEN xentryTime AND xexitTime) AS pagecount, (SELECT (xexitTime-xentryTime)/60) AS minsonsite FROM clicks WHERE $screenRestrict AND isFirstClick=1 AND clicktime&gt;'$lastupdate' ) </code></pre> <p>Thanks a lot :)</p> <p><strong>Update:</strong></p> <p>Thanks to all for the tips. I've added an index to isLastClick and managed to speed it up a good deal but it still takes +10 seconds on a low server load. I've identified the last bottleneck and marked it below. Is there any better way to select the first "isLastClick" record that is later than xentrytime?</p> <pre><code>SELECT clientid, screenid, id AS hitid, pageid AS entrypageid, clicktime AS xentrytime, (SELECT name FROM pages WHERE id = entrypageid) AS entrypagename, (SELECT clicktime FROM clicks WHERE clicktime &gt; xentrytime //&lt;&lt;removing this cuts 8.5 seconds!! AND screenid = '2' AND islastclick = 1 LIMIT 1) AS xexittime, (SELECT COUNT(1) FROM clicks WHERE screenid = '2' AND clicktime BETWEEN xentrytime AND xexittime) AS pagecount, (SELECT ( xexittime - xentrytime ) / 60) AS minsonsite FROM clicks WHERE screenid = '2' AND isfirstclick = 1 AND clicktime &gt; '1318961057' </code></pre>
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    1. UScronoklee
    1. UScronoklee
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    1. COfirstly you should run `explain` for every of your select queries to understand where can be performance issue. and check indexes.
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      1. USuser973254
    2. COtried adding indexes to the columns you query on?
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      1. USJonathan Kuhn
    3. COCool didnt know about "explain" - I'll look at it. All the "ID" columns are primary keys. I dont think there's any other unique data in the clicks table so I'm not sure there's any way to add indexes?
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