PHP Classes

PHP Preemptive Cache: Cache a limited amount of data records in memory

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Version License PHP version Categories
preemptive-cache 1.1MIT/X Consortium ...5.3PHP 5, Cache
Description 

Author

Joseluis Laso

This class can cache a limited amount of data records in memory.

It takes a callable function as parameter that will be used to retrieve data records to be cached.

When the application needs to fetch a data record, the class will call the given callable function if the record with a given id is not yet cached in memory in class array.

The class will maintain up to a given limit of cached data records in memory.

Innovation Award
PHP Programming Innovation award nominee
September 2015
Number 2		 Some algorithms need to access information records multiple times during the execution of the algorithm.

For this type of algorithm it more efficient to keep the most frequently accessed records of information memory.

This class implements a caching method that does that. It retrieves data records into a cache array up to a limited amount of records so it avoids using too much memory.

The use of configurable callback function allows it to be used to retrieve cached records from virtually any type of data source.

Manuel Lemos
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Name: Joseluis Laso <contact>
Classes: 16 packages by
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Age: 57
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Winner: 2x

Example

<?php

$startTime = intval(date("U"));

require_once __DIR__.'/../vendor/autoload.php';

use JLaso\ToolsLib\ProgressBar;
use JLaso\ToolsLib\PreEmptiveCache;

$options = getopt("h::u::p::d::");

$host = isset($options['h']) ? $options['h'] : 'localhost';
$user = isset($options['u']) ? $options['u'] : 'root';
$password = isset($options['p']) ? $options['p'] : '';
$database = isset($options['d']) ? $options['d'] : 'test';

$conn = mysqli_connect($host, $user, $password, $database);

if (!$conn){
    die(mysqli_error($conn));
}

$nRecords = mysqli_query($conn, 'SELECT COUNT(*) AS `qty` FROM `data`;')
    ->fetch_object()
    ->qty;

$xml = new DOMDocument("1.0");
$xml->formatOutput = true;
$xml->encoding = 'UTF-8';

$root = $xml->appendChild(new DOMElement('records'));

$debug = false;

if (!$debug) {
    $pBar = new ProgressBar($nRecords);
}

$familyCache = new PreEmptiveCache(function($id) use ($conn){
    return mysqli_query(
        $conn,
        sprintf(
            'SELECT `p`.`name` AS `product_name`, `p`.`ratio` AS `product_ratio`, '.
            '`p`.`family_id` AS `family_id`, `f`.`name` AS `family_name`, `f`.`ratio` AS `family_ratio` ' .
            'FROM `product` as `p` '.
            'LEFT JOIN `family` AS `f` ON `p`.`family_id`=`f`.`id` '.
            'WHERE `p`.`id`= %d',
            $id
        )
    )->fetch_assoc();
}, array(
    'maxRecordsCached' => 99999,
    'mode' => PreEmptiveCache::LESS_OLDEST_MODE,
    'debug' => $debug,
));

$totalCost = 0;
$offset = 0;
while ($offset < $nRecords){

    $record = mysqli_query($conn, 'SELECT * FROM `data` LIMIT 1 OFFSET '.$offset)->fetch_assoc();

    $xmlRecord = $root->appendChild(new DOMElement('record'));
    $xmlRecord->setAttribute('id', $record['id']);
    $xmlRecord->appendChild(new DOMElement('family', $record['product_id']));
    $xmlRecord->appendChild(new DOMElement('cost', $record['cost']));

    $product = $familyCache->fetch($record['product_id']);

    $productRatio = isset($product['product_ratio']) ? $product['product_ratio'] : 0;
    $familyRatio = isset($product['family_ratio']) ? $product['family_ratio'] : 0;
    $realCost = $record['cost'] * $productRatio * $familyRatio;

    $xmlRecord->appendChild(new DOMElement('relative_cost', $realCost));
    $xmlRecord->appendChild(new DOMElement('product', $product['product_name']));

    $totalCost += $realCost;
    $offset++;

    if (!$debug){
        $pBar->updateValue($offset);
    }
}

print "\n";

$xml->appendChild(new DOMElement('total_cost', $totalCost));
print $xml->saveXML();

print sprintf("this script lasted %d seconds !\n", intval(date("U")-$startTime));

Details

PreEmptiveCache

A little class to help improve our scripts that access to a large quantity of data.

A class to document the article I published on PHPClasses.

Once the repo is in your drive run `composer dumpautoload` in order to generate the appropriate autoload files.


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  Accessible without login Plain text file PreEmptiveCache.php Class Class source
  Accessible without login Plain text file ProgressBar.php Class Class source
  Accessible without login Plain text file RandomTokenizer.php Class Class source

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