>Why would two reads on the same record cause a lock?
it depends on which transactional level the 2 sessions are.
if the 2 are in serializable mode, everything they touch in common will make the other one to wait on that same resource... because further down the transaction, a update might occur etc...
for single queries, there is no issue, though, as you say, they just will issue a read shared lock, and can both continue without actually blocking each other
it depends on which transactional level the 2 sessions are.
if the 2 are in serializable mode, everything they touch in common will make the other one to wait on that same resource... because further down the transaction, a update might occur etc...
for single queries, there is no issue, though, as you say, they just will issue a read shared lock, and can both continue without actually blocking each other