Podcast
Questions and Answers
What is the term used to describe the attribute or group of attributes used to search for records in a sequential file?
What is the term used to describe the attribute or group of attributes used to search for records in a sequential file?
Search Key
Searching for a record in a sequential file structure is usually expensive.
Searching for a record in a sequential file structure is usually expensive.
True
An index is a data structure used to make searching for records faster.
An index is a data structure used to make searching for records faster.
True
Indexes are typically stored only in Main Memory (MM).
Indexes are typically stored only in Main Memory (MM).
Signup and view all the answers
What are the two main types of indexes based on the ordering of the data file?
What are the two main types of indexes based on the ordering of the data file?
Signup and view all the answers
What type of index is used when the data file is ordered according to the key attribute?
What type of index is used when the data file is ordered according to the key attribute?
Signup and view all the answers
What type of index is used when the data file is not ordered?
What type of index is used when the data file is not ordered?
Signup and view all the answers
When several attributes are used in the search conditions, what is the recommended approach to optimize searches?
When several attributes are used in the search conditions, what is the recommended approach to optimize searches?
Signup and view all the answers
What is the primary index?
What is the primary index?
Signup and view all the answers
What is the alternative to traditional secondary indexes when the primary index search key is unique?
What is the alternative to traditional secondary indexes when the primary index search key is unique?
Signup and view all the answers
Bitmaps are primarily used for low cardinality attributes.
Bitmaps are primarily used for low cardinality attributes.
Signup and view all the answers
What is the term for a multi-level index structure where indexes are stored in both Main Memory and Secondary Memory?
What is the term for a multi-level index structure where indexes are stored in both Main Memory and Secondary Memory?
Signup and view all the answers
What is the purpose of maintaining separate indexes for each attribute in a multi-key search scenario?
What is the purpose of maintaining separate indexes for each attribute in a multi-key search scenario?
Signup and view all the answers
It is necessary to update secondary indexes when performing either logical or physical deletions of records.
It is necessary to update secondary indexes when performing either logical or physical deletions of records.
Signup and view all the answers
What is a common approach to logically delete a record in a sequential file structure?
What is a common approach to logically delete a record in a sequential file structure?
Signup and view all the answers
What is the primary advantage of using bitmap indexes?
What is the primary advantage of using bitmap indexes?
Signup and view all the answers
Explain how to find records matching specific values for two attributes (A and B) using bitmap indexes.
Explain how to find records matching specific values for two attributes (A and B) using bitmap indexes.
Signup and view all the answers
Study Notes
Chapter 3: Indexed Files
- Indexed files are used to quickly search for records.
- Sequential search in large files is inefficient.
- Search keys are used to locate records.
- Examples include weather data files with attributes like city, date, and temperature.
- Single-key access involves searching for records matching a specific attribute value, like finding all records where the city is "DJELFA."
- Multi-key access involves searching for records matching multiple attribute values, such as "city < 'MZZZ' AND city > 'ME'."
- Indexes are data structures in main memory (MM) and/or secondary memory (SM).
- An index is an ordered table containing key-value pairs and record addresses.
- Indexes speed up record searches by providing quick access to the desired records.
- Index usage can involve various operations.
Index Usage
- Searching records uses indexes to locate the data records quickly.
- Exact searches and range queries can use indexes effectively.
- Indexing tables can be stored in main memory (MM).
- Record insertion/deletion can update the index in memory.
- Creating empty and existing indexes requires filling the index tables according to the data file.
- Backup indexes are stored in secondary memory (SM).
- Index files in secondary memory are loaded into the memory to use it.
Multi-valued Key Attribute
- Key values can be unique or multiple.
- An index can be created for multiple values and attributes.
Sparse Index
- Sparse indexes are used when the data file is ordered.
- A sparse index does not contain all possible values.
- Each entry in the index table contains the highest key in a group of consecutive blocks.
- Using a sparse index in tandem with a sequential index file is an effective setup.
Dense Index
- Dense indexes contain all key values when the order of the data file is not important.
- All values of the key attribute are included in the index.
Insertion Example
- Insertion into a file with a dense index and single-value keys involves a binary search in the index.
- Adding a new record involves writing the new record at the end of the file and updating/inserting the reference in the index.
- Insertion operations may split blocks in the file to keep the efficiency of the search.
- Handles cases where a key may appear more than once in the file.
Index/Data file with Overflow Area
- A sparse index is used with main memory (MM) to speed up access into the data file.
- The data file is located in secondary memory (SM) and contains both a primary and a secondary overflow area, useful when the insertion operation causes the file to overflow.
Index for LOF File
- Similar to the index for a TOF file (with or without overflow).
- It's used to quickly access information within the data file.
Index in MM as a Binary Search Tree
- Indexes in primary memory (MM) can be organized as binary search trees to enable efficient searching.
Large Index
- When the index is too large for primary memory (MM), secondary memory (SM) is used.
- Organized as an ordered file with contiguous blocks.
Multilevel Index
- Indexes can be organized into multiple levels to handle large files in secondary memory (SM).
Multi-Key Access
- Multi-key access involves searching using more than one attribute value.
- Primary and secondary indexes can efficiently manage searches.
- Data files can be organized according to primary indexes for multi-key search optimization.
Bitmap Indexes
- Bitmap indexes are beneficial for attributes with a limited number of possible values.
- Use binary strings of fixed length for each value.
- Useful for fast searches when the data values are limited.
- Effective for processing multi-key queries using bitwise operations.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the concepts of indexed files in this quiz. Learn about the importance of search keys and how they enhance the efficiency of locating records. Understand the differences between single-key and multi-key access in file management.
