Ok, have made patch
https://reviews.mahara.org/#/c/9950/
And tested in the following way:
// Old way
$stime = time();
log_debug('start: ' . $stime);
for ($i = 1; $i <= 10000; $i++) {
require_once('ddl.php');
$table = new XMLDBTable('view_access');
$field = new XMLDBField('id');
if (field_exists($table, $field)) { }
if (($i % 1000) == 0) {
log_debug('.');
}
}
$etime = time();
log_debug('end: ' . $etime);
log_debug($etime - $stime);
had time diff of approx 130 seconds per run for postgres
had time diff of approx 90 seconds per run for mysql
// vs New way
$stime = time();
log_debug('start: ' . $stime);
for ($i = 1; $i <= 10000; $i++) {
if (column_exists('view_access', 'id')) { }
if (($i % 1000) == 0) {
log_debug('.');
}
}
$etime = time();
log_debug('end: ' . $etime);
log_debug($etime - $stime);
had time diff of approx 40 seconds for postgres
had time diff of approx 4 seconds for mysql
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https://bugs.launchpad.net/bugs/1827445
Title:
Improve efficiency when checking if a table field exists
Status in Mahara:
In Progress
Bug description:
When upgrading we use a field_exists() check to see if a table has a
certain column or not which is fine there as upgrade chunks are a one-
time execution run when users are all logged out.
However we have begun to use field_exists() within other parts of the
code and so this can get called on every page load by multiple users
at once. This requires fetching the ddl.lib file and setting ul an
XMLDB table object and an XMLDB field object which has overhead.
Instead we should just query the database directly and ask it if the
table has the column or not
So instead of doing:
require_once('ddl.php');
$table = new XMLDBTable('tablename');
$field = new XMLDBField('fieldname');
if (field_exists($table, $field)) {
...
}
We could just do:
if (column_exists('tablename', 'fieldname')) {
...
}
And have the column_exists function that call the database directly
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