从视图中选择时 Postgres 崩溃

Question

我在 Postgres 中有一个视图，其定义如下：

CREATE VIEW participant_data_view AS
SELECT participant_profile.*,
        "user".public_id, "user".created, "user".status, "user".region,"user".name, "user".email, "user".locale,
        (SELECT COUNT(id) FROM message_log WHERE message_log.target_id = "user".id AND message_log.type = 'diary') AS diary_reminder_count,
        (SELECT SUM(pills) FROM "order" WHERE "order".user_id = "user".id AND "order".status = 'complete') AS pills
FROM participant_profile
    JOIN "user" ON "user".id = participant_profile.id
;

视图创建工作正常。但是，当我查询视图 SELECT * FROM participant_data_view 时，postgres 崩溃了

10:24:46.345 WARN  HikariPool-1 - Connection org.postgresql.jdbc.PgConnection@172d19fe marked as broken because of SQLSTATE(08006), ErrorCode(0)                                                                            c.z.h.p.ProxyConnection
org.postgresql.util.PSQLException: An I/O error occurred while sending to the backend.

this question 向我建议，这可能是导致它崩溃的内部断言。

如果我从视图定义中删除 diary_reminder_count 字段，则选择工作正常。

我做错了什么？如何修复或更改视图以便以不同的方式查询相同的数据？

请注意，创建视图工作正常，它只会在查询时崩溃。

我尝试从 IntelliJ 查询控制台运行 explain (analyze) select * from participant_data_view;，它只返回

[2020-12-08 11:13:56] [08006] An I/O error occurred while sending to the backend.
[2020-12-08 11:13:56] java.io.EOFException

我使用psql 运行相同，它返回了

my-database=# explain (analyze) select * from participant_data_view;
server closed the connection unexpectedly
    This probably means the server terminated abnormally
    before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.

查看日志文件，它包含：

2020-12-08 10:24:01.383 CET [111] LOG:  server process (PID 89670) was terminated by signal 9: Killed: 9
2020-12-08 10:24:01.383 CET [111] DETAIL:  Failed process was running: select "public"."participant_data_view"."id", "public"."participant_data_view"."study_number", <snip many other fields>,
"public"."participant_data_view"."diary_reminder_count", "public"."participant
2020-12-08 10:24:01.383 CET [111] LOG:  terminating any other active server processes

Answer 1

Linux 内核内存不足杀手很可能会因为系统内存不足而终止您的查询。

要么限制数据库会话的数量（例如使用连接池），要么减少work_mem。

在内核中设置vm.overcommit_memory = 2 并适当调整vm.overcommit_ratio 通常是个好主意。