convert_null works wrong

[alexandrim0]

Hi!

I set convert_null = true but it returns ["NULL"] but not ngx.null It is completely unusable! I belive it should not works like that. May be it broken with pgsql 11?

[leafo]

By default convert_null will convert null to the value stored in Postgres.NULL, which is a unique table {"NULL"}. If you want to have it convert to something else then you can override the Postgres.NULL value.

https://github.com/leafo/pgmoon#converting-nulls

pgmoon is runtime agnostic, so it does not default to ngx.null

[alexandrim0]

Ok, you are right, pgmoon is runtime agnostic and it is good! But you also use cjson which also have cjson.null user type represents SQL NULL same way as ngx.null does. I do not like use nullable types in SQL schemas but in some case it is correct design. pgmoon is the best lib for lua to deal with pgsql, I think. So, I need simple way to handle NULL with pgsql as I can do with mysql and etc... And now I should patch this lib to make my code works after migration from mysql to pgsql. It is no good. I guess, I am not the only one who faces this.

So, is it possible to choose which way convert_null will works? Thank you!

[leafo]

I'm not sure I follow, you can override which value gets set to null with something like this:

local pg = Postgres:new(...)
pg.convert_null = true
pg.NULL = ngx.null

local res = pg:query("select NULL")

[alexandrim0]

Great!

This works fine! It should be in readme, I think.

Thanks, you are the best!