The correct answer is: C. Hashes
Predicate indexing is a method of storing data in a database that uses predicates to index the data. A predicate is a Boolean expression that can be used to filter data. For example, the predicate “age > 18” could be used to filter a list of people to only include those who are older than 18.
Hashes are a data structure that can be used to store data in a way that is efficient for lookup. A hash function is a function that takes a key as input and produces a hash value as output. The hash value is then used to index the data in the hash table.
When using predicate indexing, the data is stored in a hash table. The key for each data item is the predicate that is used to index the data. The value for each data item is the data itself.
For example, if we have a list of people and we want to store the data in a hash table using the predicate “age > 18”, the key for each person would be the predicate “age > 18” and the value for each person would be the person’s name.
When we want to look up a person in the hash table, we would use the predicate as the key. The hash function would then be used to produce a hash value. The hash value would then be used to index the data in the hash table. The data at that index would be the person’s name.
The following are the other options and their explanations:
- A. Lists
Lists are a data structure that can be used to store data in a linear order. The data in a list is stored in consecutive memory locations. To access a data item in a list, we need to know its index in the list.
Lists are not efficient for lookup. To look up a data item in a list, we need to iterate through the list until we find the data item. This can be slow if the list is large.
- B. Stacks
Stacks are a data structure that can be used to store data in a last-in-first-out (LIFO) order. The data in a stack is stored in a linear order. The data item that is added to the stack last is the data item that is removed from the stack first.
Stacks are not efficient for lookup. To look up a data item in a stack, we need to iterate through the stack until we find the data item. This can be slow if the stack is large.
- D. None of the mentioned
This option is not correct. The buckets are stored in a hash table in predicate indexing.