Cakephp 1.3.14 not loading database schema - mysql

Question

We recently made some changes to our site to prepare it for pre-production:
Moved to a load-balanced architecture
Now use memcache/memcached to maintain session data
Enabled APC
Now, everything was working until we made some change that we cannot recall that has caused the database to not load schema properly. Here is an output of some debug:
Warning (512): SQL Error: 1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1 [CORE/cake/libs/model/datasources/dbo_source.php, line 684]
Query: SHOW FULL COLUMNS FROM
Warning (2): Invalid argument supplied for foreach() [APP/models/datasources/dbo/dbo_mysql.php, line 127]
Warning (2): array_keys() expects parameter 1 to be array, boolean given [CORE/cake/libs/model/datasources/dbo_source.php, line 1968]
Notice (8): Trying to get property of non-object [CORE/cake/libs/model/datasources/dbo_source.php, line 812]
Query: SHOW FULL COLUMNS FROM
Query: SHOW FULL COLUMNS FROM
Query: SHOW FULL COLUMNS FROM
Query: SHOW FULL COLUMNS FROM
Query: SHOW FULL COLUMNS FROM
Query: SHOW FULL COLUMNS FROM
As you can see, it is not loading the table names.
The other problem we noticed, is that when the query is generated, it is generated like this:
SELECT Project.id FROM AS Project WHERE 1=1
Notice that there is no table name, it simply tries to create the alias on a blank table name.
Any thoughts?

Answer 1

We recently made some changes to our site to prepare it for pre-production:
Thankfully you version-control your code changes and can simply roll back until you find a working version and compare to find the breaking change. With git this is easily done using git bisect.
No? Well..
Debug and identify the cause
As with any error - step one should be to look at where the error is coming from:
// cake/models/datasources/dbo/dbo_mysql.php
$cols = $this->query('SHOW FULL COLUMNS FROM ' . $this->fullTableName($model));
foreach ($cols as $column) { // #127
What should be clear here, is that Cake is unable to determine the full table name for your model.
You're trying to query a model with no table
Looking at the source for fullTableName:
// cake/libs/model/datasources/dbo_source.php
function fullTableName($model, $quote = true) {
if (is_object($model)) {
$table = $model->tablePrefix . $model->table;
} elseif (isset($this->config['prefix'])) {
$table = $this->config['prefix'] . strval($model);
} else {
$table = strval($model);
}
if ($quote) {
return $this->name($table);
}
return $table;
}
It should be clear that the model has no table according to cake.
Common causes:
The model property useTable is set to false
No describe permissions
Given the info in the question - it's most likely the first is the reason.