1 / 12

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/. The provided files. Makefile  Modify this file to include .C files as you proceed

ilori
Download Presentation

B+ Tree Implementation Details for Minibase

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. 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

  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  Scansover 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 internallyThey 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) DB::add_file_entry(name, headerPageId) 3 ( 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 //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. 4 Inserting Keys in a B+ Tree The usage of newchildentry Before inserting 5 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 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

More Related