Hi! So I was looking at the optimizer code a little bit tonight and came across something I'm not sure about. Basically, I'm wondering why is there a need for the POSITION struct in the optimizer?
>From what I can understand, an array of POSITION objects is used to represent a query plan during optimization and once an optimal query plan is chosen, this array of POSITION objects is copied into an array of JoinTable objects (in get_best_combination()). Then during execution time, the array of JoinTable objects represents the query execution plan. What I'm wondering is why not just use an array of JoinTable objects during both optimization and execution? If you look at the POSITION structure, it actually contains a pointer to a JoinTable object with just a few additional members. In theory, could we just extend JoinTable with the members from POSITION and remove the POSITION structure? Is there something I am missing here (very likely as I'm just starting to look at the optimizer)? Is there some specific reason things are designed like this? -Padraig _______________________________________________ Mailing list: https://launchpad.net/~drizzle-discuss Post to : [email protected] Unsubscribe : https://launchpad.net/~drizzle-discuss More help : https://help.launchpad.net/ListHelp
