having json fields in tables causing "could not identify an equality operator for type json"

[lagleki]

probably caused by UNION

[lagleki]

can we apply hasura/graphql-engine#2036?

[mitar]

Oh, I know about Hasura and was testing its reactivity, but I never thought of checking how it is implemented. :-) This now lead me to looking at their code, pretty cool.

[mitar]

I have asked this question on the postgresql general mailing list.

So this fails when this package is trying to determine inside the UPDATE trigger handler if a table really changed. There are few questions here:

• it is unclear how expensive such check is, it might be better to not even do it and just assume something always changed (but only rows effect by an update are checked)
• comparison is done using normal equality operator which fails for JSON (if tails inside EXCEPT operator, not UNION ALL)
• is there a better way to compare two sets of rows for changes or determining if something really changed?
• using composite equality type operator, which is what Hasura fails back to, does the comparison using the binary representation, but I am unsure how fast that is (I assume that EXCEPT operator uses indices to speed things up, which require regular equality operator)
• maybe there is a need for *EXCEPT operator, but again, not sure how fast that might be

Anyway, I made a change now that if the comparison of tables fails, then it just assumes something changed.