better check of existence of tables.

framework/yii/db/ActiveRecord.php

@@ -275,10 +275,16 @@ class ActiveRecord extends Model
 	/**
 	 * Returns the schema information of the DB table associated with this AR class.
 	 * @return TableSchema the schema information of the DB table associated with this AR class.
+	 * @throws InvalidConfigException if the table for the AR class does not exist.
 	 */
 	public static function getTableSchema()
 	{
-		return static::getDb()->getTableSchema(static::tableName());
+		$schema = static::getDb()->getTableSchema(static::tableName());
+		if ($schema !== null) {
+			return $schema;
+		} else {
+			throw new InvalidConfigException("The table does not exist: " . static::tableName());
+		}
 	}
 
 	/**

framework/yii/db/mysql/Schema.php

@@ -181,12 +181,12 @@ class Schema extends \yii\db\Schema
 	 */
 	protected function findColumns($table)
 	{
-		$sql = 'SHOW FULL COLUMNS FROM ' . $this->quoteSimpleTableName($table->name);
+		$rows = $this->db->createCommand("SHOW TABLES LIKE " . $this->quoteValue($table->name))->queryAll();
-		try {
+		if (count($rows) === 0) {
-			$columns = $this->db->createCommand($sql)->queryAll();
-		} catch (\Exception $e) {
 			return false;
 		}
+		$sql = 'SHOW FULL COLUMNS FROM ' . $this->quoteSimpleTableName($table->name);
+		$columns = $this->db->createCommand($sql)->queryAll();
 		foreach ($columns as $info) {
 			$column = $this->loadColumnSchema($info);
 			$table->columns[$column->name] = $column;