disable speculative index property finding by default

for a class
```java
class A {
   List<B> cols;
}
class B {
  String a;
}
```
for the following column 
```cols_a,cols_b```
it will map 
```
cols_a -> cols[0].a
cols_b -> cols[1]
```
which can be quote confusing when dealing with mismatched property on joins.