"cancel" query disconnects from postgres

[ccurvey]

1. set a session configuration variable (e.g. set pg_trgm.similarity_threshold = 0.8)
2. execute a long-running query. Before it finishes, hit the "cancel" button. Note that the results pane header now says "not connected"
3. now try to show your setting (e.g. show pg_trgm.similarity_threshold). You'll get an error saying unrecognized configuration parameter "pg_trgm.similarity_threshold" (which just means that the default value of 0.3 is used).

IIRC, the postgres network protocol supports an out-of-band cancellation message that won't cause the connection to be closed.

It's just surprising to cancel a query, and then have my environment silently changed.