[introspection] Query failure when query parallelism = 1

[igalshilman]

When setting query_parallelism = 1 we get a failure during execution with the following query:

RESTATE_ADMIN__QUERY_ENGINE__QUERY_PARALLELISM=1 \
RESTATE_WORKER__BOOTSTRAP_NUM_PARTITIONS=4 \
 ./target/debug/restate-server --wipe all

./target/debug/restate  sql
 'SELECT ss.id FROM sys_invocation_status ss LEFT JOIN sys_invocation_state sis ON ss.id = sis.id'

This however does not happen for any value >= 2.

[AhmedSoliman]

Do we still need this open?

[igalshilman]

Yep, still requires to understand / fix.

[tillrohrmann]

Could this problem have been resolved with the latest Datafusion upgrade?

[igalshilman]

Maybe, I'll try to find the time to look into it :+1: