python-psycopg2.InterfaceError：连接已关闭/ pgr_astar

我正在使用psycopg2从python访问postgresql数据库.当我尝试为最短的路径运行填充函数“ pgr_astar”时,出现错误

cur = db.cursor()
psycopg2.InterfaceError: connection already closed

基本上,发生的事情是：当pgr_astar在两点之间找不到路径时,它将导致数据库崩溃,并关闭与数据库的连接.

如何避免这种情况？

我试图用try / except隔离功能并创建自己的连接,所以如果关闭就没问题：

conn = psycopg2.connect(...)
try:
    result = getRecords(conn,query_pgr_astar)
    return float(result[0]['sum'])
except:
    return 500000000.0
conn.close()

但是在这种情况下,我收到了

cur.execute(query)
psycopg2.DatabaseError: SSL SYSCALL error: EOF detected

如何管理不可能的路径？

(我对pgdb和旧的shortest_path_astar函数做了同样的操作(现在不再可用),我没有问题)

PostgreSQL日志是：

2013-11-27 15:54:35 CET LOG:  terminating any other active server processes
2013-11-27 15:54:35 CET WARNING:  terminating connection because of crash of another server process
2013-11-27 15:54:35 CET DETAIL:  The postmaster has commanded this server process to roll back the current transaction and exit, because another server process exited abnormally and possibly corrupted shared memory.
2013-11-27 15:54:35 CET HINT:  In a moment you should be able to reconnect to the database and repeat your command.
2013-11-27 15:54:35 CET WARNING:  terminating connection because of crash of another server process
2013-11-27 15:54:35 CET DETAIL:  The postmaster has commanded this server process to roll back the current transaction and exit, because another server process exited abnormally and possibly corrupted shared memory.
2013-11-27 15:54:35 CET HINT:  In a moment you should be able to reconnect to the database and repeat your command.
2013-11-27 15:54:35 CET LOG:  all server processes terminated; reinitializing
2013-11-27 15:54:35 CET LOG:  database system was interrupted; last known up at 2013-11-27 15:42:01 CET
2013-11-27 15:54:35 CET LOG:  database system was not properly shut down; automatic recovery in progress
2013-11-27 15:54:35 CET LOG:  record with zero length at 65/80875D60
2013-11-27 15:54:35 CET LOG:  redo is not required
2013-11-27 15:54:35 CET LOG:  autovacuum launcher started
2013-11-27 15:54:35 CET LOG:  database system is ready to accept connections

我做的查询是：

SELECT SUM(t2.length) FROM (SELECT id2 FROM pgr_astar('SELECT edge_id AS id, vertex_id1 AS source, vertex_id2 AS target, ' || '(CASE WHEN door = ''S'' THEN -1.0  ELSE  (length * (CASE network WHEN ''0'' THEN 1.0  WHEN ''10'' THEN 1.2  WHEN ''20'' THEN 1.5  WHEN ''30'' THEN 2.0  ELSE 1.0  END) *  (CASE type WHEN ''9.1'' THEN CASE WHEN level1 < level2 THEN 3.0 ELSE 2.0 END  WHEN ''9.2'' THEN CASE WHEN level1 < level2 THEN 15.0 ELSE 12.0 END  ELSE 1.0  END) +  (CASE type WHEN ''9.3'' THEN 40.0  ELSE 0.0  END)  )  END)::float8 AS cost, ' || '(CASE WHEN door_rev = ''S'' THEN -1.0  ELSE  (length * (CASE network WHEN ''0'' THEN 1.0  WHEN ''10'' THEN 1.2  WHEN ''20'' THEN 1.5  WHEN ''30'' THEN 2.0  ELSE 1.0  END) *  (CASE type WHEN ''9.1'' THEN CASE WHEN level1 < level2 THEN 3.0 ELSE 2.0 END  WHEN ''9.2'' THEN CASE WHEN level1 < level2 THEN 15.0 ELSE 12.0 END  ELSE 1.0  END) +  (CASE type WHEN ''9.3'' THEN 40.0  ELSE 0.0  END)  )  END )::float8 AS reverse_cost, ' || 'x1, y1, x2, y2 FROM edges', " + str(destination_route) + ", " + str(origin_route) + ", TRUE, TRUE)) as t1, edges as t2 where t1.id2 = t2.edge_id

door =“ S”表示门已关闭,在这种情况下,值为-1.

解决方法:

我假设您可以在python中检查连接状态(我不使用python),以便您可以恢复并做一些明智的事情,例如重新连接.在重新连接之前,您可能需要休眠几秒钟以使数据库从崩溃中恢复.

关于灌浆问题,我希望看到一个简单的测试用例,它可以在pgadmin或psql shell中重现此问题,并作为错误提交,因此我可以对其进行调查.我们的代码永远都不会使服务器崩溃,但是有时它会使服务器崩溃,因此我们需要修复这些问题.

标签：a-star,postgresql,psycopg2,python,pgrouting
来源： https://codeday.me/bug/20191122/2059797.html