RE: [PHP] What search algorithm does in_array() use?
- From: lturmelle@xxxxxxxxxxxx ("Ligaya A. Turmelle")
- Date: Wed, 31 Jan 2007 12:37:52 +1000
Don't use a theta join - use a left, right or inner preferably with ANSI
syntax and make sure you indexes are set up correctly - this shouldn't
take very long to execute at all.
SELECT d.account
FROM data d
INNER JOIN accesslist a
USING account (or ON d.account=a.account)
WHERE a.username='username'
Respectfully,
Ligaya Turmelle
Systems Analyst
Guamcell Communications
Phone: (671)689-2377
-----Original Message-----
From: Ken Dozier [mailto:kdozier@xxxxxxxxxx]
Sent: Wednesday, January 31, 2007 6:31 AM
To: ceo@xxxxxxxxx
Cc: php-general@xxxxxxxxxxxxx; 'Gregory Beaver'
Subject: RE: [PHP] What search algorithm does in_array() use?
Thanks to all for your input, guys.
Regarding the construction of the SQL query, I would love to try it with
SUBSELECTs; but, alas, we are using RHEL 3 which ships with MySQL 3.23.
I don't think RH supports any 4.0 or later versions of MySQL on RHEL 3,
so I'm stuck with 3.23 for the time being. I had tried a query like
this:
SELECT d.account FROM data AS d, accesslist AS a WHERE
d.account=a.account AND a.username='username'
but it also took quite a bit of time. Since the problem would appear
for only a few users, I may have to simply hard code a workaround for
the time being and then come back to it later.
Thanks again for all of your help.
Ken.
-----Original Message-----
From: Richard Lynch [mailto:ceo@xxxxxxxxx]
Sent: Monday, January 29, 2007 6:13 PM
To: Ken Dozier
Cc: php-general@xxxxxxxxxxxxx
Subject: Re: [PHP] What search algorithm does in_array() use?
On Mon, January 29, 2007 11:20 am, Ken Dozier wrote:
Does in_array() use a search algorithm (i.e., binary search), or does
it check sequentially each element in the array?
Since there is no guarantee that the elements are in any particular
order, it almost has to be sequential...
I am using in_array() within a while{} loop to check query results
against an access-list array to produce a third array containing items
that successfully passed the comparison test. Because the two
starting arrays in the worst-case scenario can have 8,000 items each,
the loop is timing out.
Advice or alternative methods are appreciated.
Code Sample:
<?php
function check_results($results, $access_list) { # Check for $results
in array $access_list and
# add matches to array $match.
$result = false;
$match = array();
while ($r = mysql_fetch_row($results))
{ if ( in_array($r[0], $access_list) )
{ $match[] = $r; }
}
if ( count($match) > 0 ) { $result = $match; }
return $result;
}
?>
Ideal #1:
Figure out how to write an SQL query to find what's in the DB, and don't
do any search in PHP at all.
Ideal #2:
Put the values in as keys, and use http://php.net/isset This will "hash"
the values and have an O(1) lookup, I think.
Only works if you know the uniqueness of the values to be searched, or
don't care about duplicates.
--
Some people have a "gift" link here.
Know what I want?
I want you to buy a CD from some starving artist.
http://cdbaby.com/browse/from/lynch
Yeah, I get a buck. So?
--
PHP General Mailing List (http://www.php.net/) To unsubscribe, visit:
http://www.php.net/unsub.php
.
- Prev by Date: ereg() problem
- Next by Date: regarding ereg() problem
- Previous by thread: ereg() problem
- Next by thread: regarding ereg() problem
- Index(es):
Relevant Pages
|
