DB Client hangs when writing large string to text field (psql)

[Ayman250]

I'm using the db client to write a string directly into a text field in a local psql db.

auto clientPtr = drogon::app().getDbClient("psql");

auto f = clientPtr->execSqlAsyncFuture("INSERT INTO public.knowledge (userid, knowledge) VALUES ($1, $2)",
                                       userid, knowledge);
auto result = f.get();

std::cout << result.affectedRows() << " rows updated!" << std::endl;

This works fine, except when the string is too long. In this case 6.5 million characters, it hangs seemingly indefinitely. This is odd because when I use the pqxx psql library, it has no trouble writing strings of that length. Is there something I'm missing here?

Additional Context: I've found that the issue pops up when the knowledge from the query above gets to around 393,000-394,000 characters, I'm not sure what the exact number is. Also, It seems like there's some hard cap (that is, the query is always super quick or it just waits indefinitely). It doesn't slow down when the the length of the query approaches some limit or anything like that.

Update: It seems that the 393,216 characters is a hard cap for the the character count of knowledge here. (393,266) characters in the whole query.

Here is a demo project that demonstrates this issue:
https://github.com/Ayman250/drogondbtest
(Relevant code in InsertCtrl.cc)

Fixed in: #1599

[Ayman250]

I think I've more or less confirmed that this has nothing to with Drogon and the problem lies elsewhere likely with my psql server configuration. If anyone has any ideas on it could be, any advice would be appreciated, but I'll close this discussion for now since it's technically off topic.

[Ayman250]

Actually it seems like it may be an issue with the client and not the db. The wait event is (Client: ClientRead).

[Ayman250]

If I run a similar query using a prepared statement with the libpq library it seems to work.

[an-tao]

Would you please make a demo project that can reproduce this issue? I'll figure it out.

[Ayman250]

Thanks! I'll try to have one ready by the morning (CST).

[Ayman250]

https://github.com/Ayman250/drogondbtest
Look at InsertCtrl.cc. Increasing knowledge_param_length results in a hung query for me.

Let me know if more is needed.