index maybe not used on maintenance

[MengqiWu]

in apply_delta() maybe just use all attributes not consider the index created when create ivm
/*
* For views without aggregates, all attributes are used as keys to identify a
* tuple in a view.
*/
if (!query->hasAggs)
keys = lappend(keys, attr);

[yugo-n]

// I'm sorry for late replay.

Thank you for your feedback! That's good point.
Actually, the index is used even when all attributes are used as a key, but we don't have to use some attributes if we have a unique key. I'll consider to fix this.