/**
* Attepts to find a column on a foreign table.
* Walks up table inheritance chains.
* If the foreign column is itself a foreign key, resolves the type of that column before returning.
*/
private static function resolve_foreign_column($db_doc, $local_schema, $local_table, $local_colname, $foreign_schema, $foreign_table, $foreign_colname, $visited = array())
{
// walk up the foreign table inheritance chain to find the foreign column definition
$fschema = $foreign_schema;
$ftable = $foreign_table;
do {
$foreign_column = dbx::get_table_column($ftable, $foreign_colname);
if ($ftable['inheritsSchema']) {
$fschema = dbx::get_schema($db_doc, (string) $ftable['inheritsSchema']);
}
if ($ftable['inheritsTable']) {
$ftable = dbx::get_table($fschema, (string) $ftable['inheritsTable']);
} else {
$ftable = null;
}
} while (!$foreign_column && !!$fschema && !!$ftable);
if (!$foreign_column) {
// column wasn't found in any referenced tables
throw new Exception("Local column {$local_schema['name']}.{$local_table['name']}.{$local_colname} references unknown column {$foreign_schema['name']}.{$foreign_table['name']}.{$foreign_colname}");
}
// column type is missing, and resolved foreign is also a foreign key?
// recurse and find the cascading foreign key
if (empty($foreign_column['type']) && !empty($foreign_column['foreignTable'])) {
// make sure we don't visit the same column twice
$foreign_col = format::get_fully_qualified_column_name($foreign_schema['name'], $foreign_table['name'], $foreign_column['name']);
if (in_array($foreign_col, $visited)) {
$local = format::get_fully_qualified_column_name($local_schema['name'], $local_table['name'], $local_colname);
throw new Exception("Foreign key cyclic dependency detected! Local column {$local} pointing to foreign column {$foreign_col}");
}
$visited[] = $foreign_col;
$nested_fkey = self::foreign_key_lookup($db_doc, $foreign_schema, $foreign_table, $foreign_column, $visited);
// make a separate clone of the column element because we are specifying the type only for foreign key type referencing
$foreign_column = new SimpleXMLElement($foreign_column->asXML());
$foreign_column['type'] = (string) $nested_fkey['column']['type'];
}
return $foreign_column;
}
