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 http://www.cs.ucr.edu/~cs179g-t/ 1

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

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

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

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

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

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

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

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

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

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

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