1. B+ Tree Implementation Details for Minibase
Department of Computer Science
University of California – Riverside
cs179G – Database Project
B+ Tree Implementation Details for Minibase by
Demetris Zeinalipour 1

2. The provided files
Makefile  Modify this file to include .C files as you proceed
btfile.h  Definition of the B+Tree
btindex_page.h  Definition of an Index Page
btleaf_page.h  Definition of a Leaf Page
btreefilescan.h  Scans over the leaf pages using ranges
key.C  Auxiliary Functions to deal with Keys
btree_driver.C  Contains the tests (test1, …, test4)
main.C  Launches the tests
results  Sample Output Results
keys  Contains Strings (keys) that will be inserted in tree
* Bold shows the classes for which you need to provide the .C source 2

3. What needs to be implemented?
You are asked to provide functionality to:
Create/Open an Existing B+ tree
Insert Keys (char *or int) into B+ tree
Delete Keys from B+ tree
Do range queries (IndexScans)
Most Functions are based on Recursion 3

4. Revision of BTIndexPage and BTLeafPage (Inherited from SortedPage HFPage)
Necessary defs in include/bt.h
BTIndexPage
struct KeyDataEntry {
Keytype key;
Datatype data; };
union Keytype {
int intkey;
char charkey[MAX_KEY_SIZE1]; };
union Datatype {
PageId pageNo; // in index entries
RID rid; // for leaf page entries };
struct RID{ // in the tests these are fake
PageID pageID,
int slotID}
typedef enum { INDEX, LEAF } nodetype;
int keyCompare(const void* key1,
const void* key2, AttrType t);
220 bytes
BTLeafPage
From include/minirel.h
enum AttrType { attrString, attrInteger, attrReal, attrSymbol, attrNull }; 4

5. BTIndexPage and BTLeafPage internally They are like HFPage but the slot directory is sorted + the record is either <key,PageId>(Index) or <key,RID<pageId, slotId>> (leaf)
In order to iterate the entries of these pages use (should make calls to the appropriate HFPage funcs)
Status get_first(RID& curid, void *curkey, RID & dataRid); //gets 1st record with key = curkey & puts in dataRid
Status get_next (RID& curid, void *curkey, RID & dataRid); until the status becomes NOMOREREC. 5

6. The Big Picture of the Project
Application (Btree_driver.C)
 Test1() // insert randomly 2000 integers in a B+ Tree
 btf = new BTreeFile(status, "BTreeIndex", attrInteger, sizeof(int)); 1
1) DB::get_file_entry(name, &headerPageId)
2) BM::newPage(&headerPageId, &Page) 2 4
4) BM::Pin(headerPageId, &Page) 3
3) DB::add_file_entry(name, headerPageId)
( other methods) Pin, Unpin, newpage,freepage, …
BufferManager
Buf.C
Read_page, write_page, alloc/dealloc_page
Storage Manager
Db.h
Main Memory
Secondary Storage
btlog
BTREEDRIVER (the database)
BTreeIndex, OtherIndices
DataFiles (nothing for this project)
O.S files 6

7. The Header Page BTreeFile BufferManager Btfile.C Buf.C
//define in btfile.h
struct BTreeHeaderPage {
unsigned long magic0; // magic number for sanity checking
PageId root; // page containing root of tree
AttrType key_type; // type of keys in tree
int keysize; // max key length (specified at index creation)
int delete_fashion; // naive delete algorithm or full delete algorithm };
BTreeFile
Btfile.C 5 7
BM::unPin(root, &Page, dirty)
BM::Pin(root, &Page)
BufferManager
Buf.C
6) This step depends on the functionality you are implementing
e.g. for searching you are using BT.h::keycompare(void *key1, void *key2, AttrType) along with the BTIndexORLeafPage::getNext() iterator. 6 7

8. Searching a key in a B+ Tree
IndexFileScan *btfile::new_scan(const void *lo_key = NULL, const void *hi_key = NULL);
pageId
Index
Leaf 8

9. Inserting Keys in a B+ Tree
The usage of newchildentry
Before inserting 5 4
nodeptr 4 7 8 9
After inserting 5 4 7
nodeptr
newchildentry 4 5 7 8 9 9

10. Deleting Keys from a B+ Tree
No Merges or Redistributions.
We simply locate the key and delete it in a recursive fashion. 10

11. Where to start from? Create/Open an Existing B+ tree
Insert Keys (char *or int) into B+ tree
In order to implement Insert, certain functions in BTfile/BTIndexPage/BTLeafPage must be implemented.
Initially you may ignore the BTLeafPage and just create the Index Level structure of the tree.
After the insertion you will have a B+ tree on which you can perform various operations
Move on to Deletes of entries, searches (range searches) and testing/debugging. 11

12. C++ Clarifications Assert.h const int MAGIC0 = 0xfeeb1e;
Used to diagnosing logic errors in the program
const int MAGIC0 = 0xfeeb1e;
assert(headerPage->magic0 == (unsigned)MAGIC0);
if the test fails then the program will abort
BTreeFile::BTreeFile(Status &, const char *): Assertion `headerPage->magic0 == (unsigned)MAGIC0 ' failed.
Aborted 12