Hello all, I was going through the Expression Evaluator and was trying to understand how the expressions are formed and evaluated. I was informed on the IRC channel that the PARAM nodes are quite important and many well written client applications use PARAMs for sending query to the backend. I found while looking at the ExecEvalParam function that a call is made to the ExecSetParamPlan for the first time when the PARAM is caught in the ExprState tree.
I am confused about how many times the call is made to the ExecSetParamPlan funtion. Since the executor runs the expression evaluator for each tuple (trying to find qual satisfaction) while the expression tree is created only once, the possibility (from my viewpoint) is that the ExecSetParamPlan might be called once only; which would be when the first PARAM is encountered during the query execution. OR, it might get called individually for each tuple (when the PARAM node is caught in the tree). So I am confused about which case is it? Does it (ExecSetParamPlan) get called on per-tuple basis or first encounter in the qual/expression evaluation basis? Kindly help. Regards, Vaibhav -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
