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POMassive MySQL update best approach?
 

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    <p>I need to update the stock levels in my MySQL database 3 times a day from a CSV file.</p> <p>The CSV has over 27,000 products in there to be update and as you can imagine it takes a little while.</p> <p>I currently have a php script that runs the following:</p> <pre><code>select * from products where product_code = "xxxxxxx"; if num_rows &gt; 0 if new_stock_level = 0 UPDATE products SET `stock` = 0, `price` = 9.99 where product_code = "xxxxxxx"; else UPDATE products SET `stock` = 50, `price` = 9.99, `stock_date` = now() where product_code = "xxxxxxx"; </code></pre> <p>This is all well and good if you are updating &lt; 50 items but not 27,000!</p> <p>What would be the best way to do an update of this scale?</p> <p>I have been doing some reasearch and from what i can see mysqli prepared statments seem to be where i should be heading.</p> <p>After trying some of the bits mentioned below and what i have read online i have had the follwoing results with a batch of 250 updates.</p> <p>Changing from InnoDB to MyISAM on average increased the number of ubdate per sec from 7 to 27 which is a massive increase to start with.</p> <p>Prepareing the statment with case 9-10 sec</p> <pre><code>## Prepare the statment. $stmt = $mysqli-&gt;prepare("UPDATE products SET stock = case ? when 0 then 0 else ? end, price = ?, stock_date = case ? when 0 then stock_date else now() end WHERE product_code = ?"); $stmt-&gt;bind_param('dddds', $stock, $stock, $price, $stock, $prod); $stmt-&gt;execute(); </code></pre> <p>Non Prepared statment 9-10 sec</p> <pre><code>$sql = "UPDATE products SET stock = case " . $stock . " when 0 then 0 else " . $stock . " end, price = " . $price . ", stock_date = case " . $stock . " when 0 then stock_date else now() end WHERE product_code = \"" . $prod . "\";\n"; $mysqli-&gt;query($sql); </code></pre> <p>grouping statments in 50's and excuting with multi_query 9-10 sec</p> <pre><code>$mysqli-&gt;multi_query($sql); </code></pre> <p>Non prepared with 2 seperate querys depending if im updating the stock date or not. 8-9 Sec</p> <pre><code>if($stock &gt; 0) { $sql = "UPDATE products SET stock = " . $stock . ", price = " . $price . ", stock_date = now() WHERE product_code = \"" . $prod . "\";\n"; } else { $sql = "UPDATE products SET stock = " . $stock . ", price = " . $price . " WHERE product_code = \"" . $prod . "\";\n"; } $mysqli-&gt;query($sql); </code></pre> <p>prepared version of the same 8-9 sec</p> <pre><code>## Prepare statments $stmt1 = $mysqli-&gt;prepare("UPDATE products SET stock = ?, price = ?, stock_date = now() WHERE product_code = ?;"); $stmt1-&gt;bind_param('dds',$stock, $price, $prod); $stmt2 = $mysqli-&gt;prepare("UPDATE products SET stock = ?, price = ? WHERE product_code = ?;"); $stmt2-&gt;bind_param('dds', $stock, $price, $prod); if($stock &gt; 0) { $stmt1-&gt;execute(); } else { $stmt2-&gt;execute(); } </code></pre> <p>I aslo tried addeding an additional processor to the VPS and it made it about 4 querys a secound faster.</p>
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