Query Processing

Question 1

A system catalog stores _________

Answer 1

metadata

Question 2

What is metadata?

Answer 2

Information that describes the data that is managed

Question 3

Metadata and statistics about the DB are used to find the best way to _______ a query

Answer 3

evaluate

Question 4

Metadata for tables include what?

Answer 4

Table name
Filename
File structure
Attribute names
Attribute types
Name of indexes
Integrity constraints

Question 5

Metadata for indexes include

Answer 5

Index name
Index Structure
Attributes of search key

Question 6

Statistics for tables include

Answer 6

Cardinality

Size

Question 7

Statistics for indexes include

Answer 7

Index Cardinality
Index Size
Index Height
Index Range

Question 8

Declarative queries are translated into a _______ ________ to be executed

Answer 8

procedural language

Question 9

Query evaluation plans are represented as trees of ______ ________

Answer 9

relational operators

Question 10

An ______ _____ is way in which the rows of a table can be retrieved

Answer 10

Access path

Question 11

An access path consists of an _____ plus a _________ selection condition

Answer 11

index, matching

Question 12

A hash index matches conditions if there are only ______ in the conjunct

Answer 12

equalities

Question 13

A tree index matches conditions for any _________ operator

Answer 13

comparison

Question 14

The most selective access path retrieves the ______ pages

Answer 14

fewest

Question 15

_______ depends on the conjunct in index matches

Answer 15

selectivity

Question 16

What is the process for evaluating a selection?

Answer 16

• If no index on R matches conditions, we scan R

- If 1+ indexes on R match, use the most selective index to retrieve matching rows

Question 17

What is the process for evaluating a projection?

Answer 17

Scan table or index and output required subset of fields for each tuple.

Question 18

Join is the most common and ______ operation

Answer 18

expensive

Question 19

What are 5 join algorithms?

Answer 19

• Nested Loop joins
• Block nested loops join
• Index nested loop join
• Sort-merge join
• Hash join