Database Homework Help
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The document provides an overview of SimpleDB, a basic database system highlighting its components such as heapfiles, operators, and transaction management. It details the implementation of iterators, table schema creation, and database operations using code examples. Additionally, it explains how to manage heapfiles, conversion of CSV files to heapfiles, and testing procedures using the Ant tool.
![// construct a 3column table schema
Type types[] = new Type[]{ Type.INT_TYPE, Type.INT_TYPE, Type.INT_TYPE };
String names[] = new String[]{ "field0", "field1", "field2" };
TupleDesc descriptor = new TupleDesc(types, names);
// create the table, associate it with some_data_file.dat
// and tell the catalog about the schema of this table.
HeapFile table1 = new HeapFile(new File("some_data_file.dat"), descriptor);
Database.getCatalog().addTable(table1);
// construct the query: we use a simple SeqScan, which spoonfeeds
// tuples via its iterator.
TransactionId tid = new TransactionId();
SeqScan f = new SeqScan(tid, table1.id());
// and run it
f.open();
while (f.hasNext()) {
Tuple tup = f.next();
System.out.println(tup);
}
f.close();
Database.getBufferPool().transactionComplete();
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Database Homework Help
- 1. For any Homework related queries, Call us at : - +1 678 648 4277 You can mail us at :- info@databasehomeworkhelp.com or reach us at :- https://www.databasehomeworkhelp.com/
- 2. What is SimpleDB? • • A basic database system What is has – Heapfiles – Basic Operators (Scan, Filter, JOIN, Aggregate) – Buffer Pool – Transactions – SQL Frontend Things it doesn't have – Query optimizer – Fancy relational operators (UNION, etc) – Recovery – Indices • Database Systems databasehomeworkhelp.com
- 4. Catalog • Catalog stores a list of available tables, TupleDesc – void addTable(DbFile d, TupleDesc d) – DbFile getTable(int tableid) – TupleDesc getTupleDesc(int tableid) • Not persisted to disk DbIterator.java • Iterator class implemented by all operators – open() – close() – getTupleDesc() – hasNext() – next() – rewind() • Iterator model: chain iterators together databasehomeworkhelp.com
- 5. // construct a 3column table schema Type types[] = new Type[]{ Type.INT_TYPE, Type.INT_TYPE, Type.INT_TYPE }; String names[] = new String[]{ "field0", "field1", "field2" }; TupleDesc descriptor = new TupleDesc(types, names); // create the table, associate it with some_data_file.dat // and tell the catalog about the schema of this table. HeapFile table1 = new HeapFile(new File("some_data_file.dat"), descriptor); Database.getCatalog().addTable(table1); // construct the query: we use a simple SeqScan, which spoonfeeds // tuples via its iterator. TransactionId tid = new TransactionId(); SeqScan f = new SeqScan(tid, table1.id()); // and run it f.open(); while (f.hasNext()) { Tuple tup = f.next(); System.out.println(tup); } f.close(); Database.getBufferPool().transactionComplete(); databasehomeworkhelp.com
- 6. HeapFile.java • An array of HeapPages on disk • Javadoc is your friend! • Implement everything except addTuple and removeTuple HeapPage.java • Format – Header is a bitmap – Page contents are an array of fixedlength Tuples • Full page size = BufferPool.PAGE_SIZE • Number of bits in Header = number of Tuples • Header size + size of tuples = BufferPool.PAGE_SIZE databasehomeworkhelp.com
- 7. HeapFileEncoder.java • Because you haven’t implemented insertTuple, you have no way to create data files • HeapFileEncoder converts CSV files to HeapFiles • Usage: – java jar dist/simpledb.jar convert csvfile.txt numFields • Produces a file csvfile.dat, that can be passed to HeapFile constructor. BufferPool.java • Manages cache of pages – Even from inside DbFile! You will eventually implement – locking for transactions – Flushing of pages for recovery databasehomeworkhelp.com
- 8. Compiling, Testing, and Running • Compilation done through the ant tool – Works a lot like make Two kinds of tests: – Unit tests – System Tests Demo on debugging using unit tests. • • databasehomeworkhelp.com