those files are needed

exam/ex01/db_util.py

@@ -0,0 +1,28 @@
+from cfg import config
+
+def _get_page_id(title, connection):
+	cursor = connection.cursor()
+	if(config["use_sqlite"]):
+		cursor.execute("SELECT rowid FROM pages WHERE title=%s", (title,))
+	else:
+		cursor.execute("SELECT page_id FROM pages WHERE title=%s", (title,))
+	return cursor.fetchone()
+
+def get_page_id(title, connection):
+
+	result = _get_page_id(title, connection)
+	if(result is not None):
+		return result[0]
+
+	cursor = connection.cursor()
+	cursor.execute("INSERT INTO pages(title) VALUES(%s)", (title,))
+	return _get_page_id(title, connection)[0]
+
+def get_page_title(page_id, connection):
+	cursor = connection.cursor()
+	if(config["use_sqlite"]):
+		cursor.execute("SELECT title FROM pages WHERE rowid=%s", (page_id,))
+	else:
+		cursor.execute("SELECT title FROM pages WHERE page_id=%s", (page_id,))
+	return cursor.fetchone()[0]
+		

exam/ex01/graph.py

@@ -0,0 +1,54 @@
+from collections import deque, defaultdict
+import logging
+
+from cfg import config
+
+logger = logging.getLogger(__name__)
+
+
+class DijkstraHelper(object):
+	def __init__(self, nodes, connections):
+		self._nodes = {node: float("inf") for node in nodes}
+		self._connections = connections
+		self._todo_in_next_step = set()
+
+	@classmethod
+	def from_db(cls, connection):
+		cursor = connection.cursor()
+		cursor.execute("SELECT page_id FROM pages")
+		nodes = [n[0] for n in cursor.fetchall()]
+		connections = defaultdict(list)
+
+		cursor.execute("SELECT source, destination FROM links")
+		for source, destination in cursor:
+			connections[source].append(destination)
+
+		return cls(nodes, connections)
+
+	def dijkstra(self, root):
+		self.recursive_dijkstra([root], 0)
+
+	def recursive_dijkstra(self, todos, depth):
+		if(not todos):
+			return
+		logger.info("recursive_dijkstra(<{} nodes>, {})".format(len(todos), depth))
+		next_todos = deque()
+		for todo in todos:
+			next_todos.extend(self.dijkstra_one(todo, depth))
+
+		self.recursive_dijkstra(next_todos, depth + 1)
+
+	def dijkstra_one(self, node, depth):
+		for neighbor in self._connections[node]:
+			if(self._nodes[neighbor] <= depth):
+				continue
+			self._nodes[neighbor] = depth
+			yield neighbor
+
+	def write_back(self, connection):
+		cursor = connection.cursor()
+		cursor.execute("DELETE FROM dijkstra_helper")
+		cursor.executemany("INSERT INTO dijkstra_helper(page, value) VALUES(%s, %s)", list(self._nodes.items()))
+
+
+