Question

I have a script that is taking too long to run and I have been working on optimizing it to be quicker. One thing I know is taking extra time is the fact that i have to run the same query multiple times. I’d like to be able to store the result of that query (without writing it to a db) so that I can reference it’s value later without having to run the query again.

I am dramatically simplifying the script below but hopefully this gives you an idea.

Let’s say i have two functions that each return a value:

    function a(){
          $query = "SELECT SUM(price) FROM table_1 WHERE zip='$this->zip'"; 
          $result = mysql_query($query) or die(mysql_error());
          while($row = mysql_fetch_array($result)){
          return $row['SUM(price)'];
    }
    function b(){
          $query = "SELECT SUM(price) FROM table_2 WHERE zip='$this->zip'"; 
          $result = mysql_query($query) or die(mysql_error());
          while($row = mysql_fetch_array($result)){
          return $row['SUM(price)'];
    }

Let’s suppose function a() returns a value of 10 and function b() returns a value of 5

Now, suppose my script is something like this:

    if (function a() > 5) { echo 'it is greater than 5!' }
    if (function a() < 5) { echo 'it is less than 5!' }
    if (function b() == 5) { echo 'it equals 5!' }
    if (function b() > 10) { echo 'it is not greater than 5!' }

If i understand things properly, the script above causes 4 separate queries of my database. It is possible to store the initial running of each query? One thing i thought of was doing this:

    $a = function a();
    $b = function b();

And then having my script like this:

    if ($a > 5) { echo 'it is greater than 5!' }
    if ($a < 5) { echo 'it is less than 5!' }
    if ($b == 5) { echo 'it equals 5!' }
    if ($b > 10) { echo 'it is not greater than 5!' }

Will that cause the queries to only run once each at the point when i define $a and $b? Is there another method to consider that i am not thinking of?

Thanks for your help!

Answer 1

Yes, this will cause your queries to only run once. If you want to ensure that they run once per session without manually caching the result in a variable every time, you could look into an ORM with some caching ability, or use static variables inside each function:

function a() {
  static $cached_result;
  if (!is_null($cached_result) return $cached_result;

  $query = "SELECT SUM(price) FROM table_2 WHERE zip='$this->zip'"; 
  $result = mysql_query($query) or die(mysql_error());
  while($row = mysql_fetch_array($result)){
    return $cached_result = $row['SUM(price)'];
  }
}

If you don’t want to use an ORM, you should at the very least be writing your own slim series of wrapper functions around database access, rather than manually calling mysql_query in every function. There should really be only one point where your app touches the database through the mysql_* family of functions. This isolates change; had you implemented a small wrapper around your database access in the first place, you would now only have one place to change in order to ditch the dated mysql_query functions in favour of PDO.