Postgres crashes when selecting from view - postgresql

Question

I have a view in Postgres with the following definition:
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
;
The view creation works just fine. However, when I query the view SELECT * FROM participant_data_view, postgres crashes with
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 suggests to me that it might be an internal assertion that causes it to crash.
If I remove the diary_reminder_count field from the view definition, the select works just fine.
What am I doing wrong? How can I fix my view, or change it so I can query the same data in a different way?
Note that creating the view works just fine, it only crashes when querying it.
I tried running explain (analyze) select * from participant_data_view; from the IntelliJ query console, which only returns
[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
I ran the same using psql, there it returns
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.
Looking at the log files, it contains:
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

In all likelihood, the Linux kernel out-of-memory killer killed your query because the system ran out of memory.
Either restrict the number of database sessions (for example with a connection pool) or reduce work_mem.
It is usually a good idea to set vm.overcommit_memory = 2 in the kernel and tune vm.overcommit_ratio appropriately.