Hot Standby and cancelling idle queries

Recent change:

An idle-in-transaction transaction can also hold a temporary file. Think
of an open cursor, for example. Therefore, remove the distinction
between CONFLICT_MODE_ERROR and CONFLICT_MODE_ERROR_IF_NOT_IDLE,
idle-in-transaction backends need to be killed too when a tablespace is
dropped.

Open cursors still have snapshots, so they would not be treated as idle
in transaction. If the user has a held cursor then they can keep it,
since it has already read the database and released the snapshot. So
this change seems both unnecessary and harsh, since even if it is
necessary we can work out how to avoid this easily enough.

--
Simon Riggs www.2ndQuadrant.com