Module 8

Which of the following are true about B+ tree-based indexing?

- It is an index structure that ensures that all paths from the root to a leaf in a given tree are of the same height. - Finding the correct leaf page is faster than a binary search. - The lowest level of the tree - called the leaf level - contains the data entries.

When choosing a hash function to assign search key values to buckets, the function should have which of the following qualities?

- Uniform distribution. - Random distribution.

For a set of 100 data records with 5 fields per record, how many clustered indexes can there be?

1

Match the steps to insert a data entry into a B+ tree to their order

1 find the correct leaf L 2 if room put data into L; done 3 split L, redistribute entries evenly copy middle key up 4 inset index entry pointing to L2 into parent of L 5 If necessary, split index node recursively

The primary difference between a B tree indices and a B+ tree indices is which of the following?

A B-tree eliminates the redundant storage of search-key values.

When a file is organized so that the ordering of data records is the same as or close to the ordering of data entries in some index, we say that is:

A clustered index.

The time it takes for a particular hashing or indexing technique to find a particular data item, or set of items.

Access time

The time it takes for a particular hashing or indexing technique to delete a data item.

Deletion time

The key attribute of a hashing function is which of the following?

Even distribution of the entries throughout the table.

A primary index is one that includes the primary key, indexes that include only other candidate keys are called secondary indexes.

False

The ability to double the directory by simply copying the directory to the lower part is accomplished because we are using the most significant bits.

False

Static hashing is done by performing which of the following?

NOT Applying a hash function h to identify the directory entry then following the chain of buckets to the correct one.

The average number of children in a B+ tree is called what?

NOT The significance of the tree.

An indexing technique based on a sorted ordering of the values.

Ordered index

The key advantage of using a B+ tree for an index file as opposed to a hashing scheme is which of the following?

Range searches

Any attribute or set of attributes with which a file may locate a record or set of records.

Search key

A type of dense index, with an index entry for every search-key value and a pointer to every record in the file, where the records pointed to by successive values in the index are not stored sequentially.

Secondary index

The additional space occupied by an index structure for a particular hashing or indexing technique.

Space overhead

Which of the following is true about tree-structured indexing techniques?

Support both range searches and equality searches.

Both the global and the local depth use the value to identify which of the following?

The number of bits of the value returned from the hash table to use.

In an extendible hashing scheme, the directory structure is grown when which of the following is true?

The size of the local depth indicatory exceeds the global indicator after the insert.

A range search is the concept of finding all records where the seach key value is less than some value and/or greater than another value.

True

Dynamic hashing techniques allow the hash function to be modified dynamically to accommodate the growth or shrinkage of the database.

True

Extendible hashing schemes solve the problems of a static hash scheme by implementing a directory of pointers to buckets and growing the directory appropriately.

True