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Overview
Comment: | :-) (CVS 216) |
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Downloads: | Tarball | ZIP archive | SQL archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA1: |
c3e521190f02120a34f1e9244fe1ea3a |
User & Date: | drh 2001-05-11 11:02:47 |
Context
2001-05-15
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00:39 | :-) (CVS 217) check-in: ee6760fb user: drh tags: trunk | |
2001-05-11
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11:02 | :-) (CVS 216) check-in: c3e52119 user: drh tags: trunk | |
2001-04-29
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23:32 | :-) (CVS 215) check-in: 624ccbca user: drh tags: trunk | |
Changes
Changes to notes/notes2.txt.
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How to do a B*Tree insert: add_to_page(cursor, data, ptr){ if( data_fits_on_page ){ add data to page; return; } if( page==root ){ split currentpage+(data+ptr) into lowerpart, center, upperpart newpage1 = lowerpart; newpage2 = upperpart; page = ptr(newpage1) + center + ptr(newpage2); return; } if( move_some_data_left || move_some_data_right ){ add data to page return } split currentpage+(data+ptr) into lowerpart, center, upperpart newpage = upperpart currentpage = lowerpart pop cursor one level add_to_page(cursor, center, ptr(newpage)); } unlink_entry(cursor, olddata){ if( !is_a_leaf ){ n = next_entry() if( n fits pageof(cursor) ){ if( olddata!=nil ) copy dataof(cursor) into olddata copy dataof(n) into dataof(cursor) unlink_entry(n, nil) return } n = prev_entry() if( n fits pageof(cursor) ){ if( olddata!=nil ) copy dataof(cursor) into olddata copy dataof(n) into dataof(cursor) unlink_entry(n, nil) return } unlink_entry(n, leafdata) move cursor data and ptr into olddata, oldptr add_to_page(cursor, leafdata, oldptr) return } move cursor data into olddata if( !underfull(pageof(cursor)) ) return } |
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How to do a B*Tree insert: add_to_page(pageptr, data, pgno){ pgno.parent = pageptr if( data+pgno fits on pageptr ){ add data+pgno to pageptr return } if( pageptr==root ){ split pageptr+(data+pgno) into newpage1, center, newpage2 pageptr = ptr(newpage1) + center + ptr(newpage2); return } if( move_some_data_left || move_some_data_right ){ add data+pgno to pageptr return } split pageptr+(data+pgno) into pageptr, center, newpage add_to_page(parent(pageptr), center, ptr(newpage)); newpage.parent = parent(pageptr) } Cursor: pageptr, idx unlink_entry(cursor, olddata){ if( cursor.pageptr is not a leaf page ){ if( olddata!=nil) copy payload(cursor) into olddata n = next_entry(cursor) if( payloadsize(n) <= freesize(cursor) + payloadsize(cursor) ){ copy payload(n) into payload(cursor) unlink_entry(n, nil) return } p = prev_entry(cursor) if( payloadsize(p) <= freesize(cursor) + payloadsize(cursor) ){ copy payload(p) into payload(cursor) unlink_entry(p, nil) return } unlink(n, leafdata) pageptr = cursor.pageptr nextpgno = pageptr.aCell[cursor.idx].pgno; convert_cursor_to_free_block(cursor) add_to_page(pageptr, leafdata, nextpgno) return } pageptr = cursor.pageptr; convert_cursor_to_free_block(cursor) if( usage(pageptr)<0.65 ){ consolidate(pageptr) } } consolidate(pageptr){ parentpage = parentof(pageptr) idx = index_of_page(parentpage, pageptr); leftsibling = parentpage.cell[idx].pgno; rightsibling = parentpage.cell[idx+1].pgno; if( idx>0 ){ cursor = makecursor(pageptr,idx-1) if( try_to_move_down(cursor) ) return } if( idx<max ){ cursor = makecursor(pageptr,idx) try_to_move_down(cursor) } return } try_to_move_down(cursor){ pageptr = cursor.pageptr if( payload(cursor)+sizeof(left)+sizeof(right)<=pagesize ){ put cursor and content of left into right remove cursor from pageptr if( pageptr is root ){ if( cellcount(pageptr)==0 ){ copy child into pageptr update parent field of child } }else if( usage(pageptr)<0.65 ){ try_to_move_down(cursor) } } } cursor_move_next(cursor){ if( cursor.incr_noop ){ cursor.incr_noop = FALSE; return; } if( is_leaf(cursor.pageptr) ){ if( cursor.idx==cursor.pageptr.ncell ){ if( cursor.pageptr==root ){ nil cursor return } cursor_move_up(cursor) cursor_move_next(cursor) }else{ cursor.idx++; } return } pgno = next_pgno(cursor) loop { cursor.pageptr = get(pgno); if( is_leaf(cursor.pageptr) ) break; pgno = first_pgno(pageptr); } cursor.idx = 0; } |
Changes to src/btree.c.
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** Boston, MA 02111-1307, USA. ** ** Author contact information: ** drh@hwaci.com ** http://www.hwaci.com/drh/ ** ************************************************************************* ** $Id: btree.c,v 1.3 2001/04/29 23:32:56 drh Exp $ */ #include "sqliteInt.h" #include "pager.h" #include "btree.h" #include <assert.h> typedef unsigned int u32; /* ** The first page contains the following additional information: ** ** MAGIC-1 ** MAGIC-2 ** First free block */ #define EXTRA_PAGE_1_CELLS 3 #define MAGIC_1 0x7264dc61 #define MAGIC_2 0x54e55d9e /* ** Each database page has a header as follows: ** ** page1_header Extra numbers found on page 1 only. ** leftmost_pgno Page number of the leftmost child ** first_cell Index into MemPage.aPage of first cell ................................................................................ ** MemPage.pStart always points to the leftmost_pgno. First_free is ** 0 if there is no free space on this page. Otherwise it points to ** an area like this: ** ** nByte Number of free bytes in this block ** next_free Next free block or 0 if this is the end */ /* ** The maximum number of database entries that can be held in a single ** page of the database. Each entry has a 16-byte header consisting of ** 4 unsigned 32-bit numbers, as follows: ** ** nKey Number of byte in the key ................................................................................ ** next index in MemPage.aPage[] of the next entry in sorted order ** ** The key and data follow this header. The key and data are packed together ** and the total rounded up to the next multiple of 4 bytes. There must ** be at least 4 bytes in the key/data packet, so each entry consumes at ** least 20 bytes of space on the page. */ #define MX_CELL ((SQLITE_PAGE_SIZE-12)/20) /* ** The maximum amount of data (in bytes) that can be stored locally for a ** database entry. If the entry contains more data than this, the ** extra goes onto overflow pages. */ #define MX_LOCAL_PAYLOAD ((SQLITE_PAGE_SIZE-20-4*24)/4) ................................................................................ unsigned char validUp; /* True if MemPage.up is valid */ unsigned char validLeft; /* True if MemPage.left is valid */ unsigned char validRight; /* True if MemPage.right is valid */ Pgno up; /* The parent page. 0 means this is the root */ Pgno left; /* Left sibling page. 0==none */ Pgno right; /* Right sibling page. 0==none */ int idxStart; /* Index in aPage[] of real data */ int nFree; /* Number of free elements of aPage[] */ int nCell; /* Number of entries on this page */ u32 *aCell[MX_CELL]; /* All entires in sorted order */ } typedef struct MemPage; /* ** The in-memory image of a disk page has the auxiliary information appended ................................................................................ Pager *pPager; /* The page cache */ BtCursor *pCursor; /* All open cursors */ MemPage *page1; /* First page of the database */ int inTrans; /* True if a transaction is current */ }; typedef Btree Bt; /* ** The maximum depth of a cursor */ #define MX_LEVEL 20 /* ................................................................................ BtCursor *pPrev, *pNext; /* Linked list of all cursors */ int valid; /* True if the cursor points to something */ int nLevel; /* Number of levels of indexing used */ BtIdxpt *pLevel; /* Pointer to aLevel[nLevel] */ BtIdxpt aLevel[MX_LEVEL]; /* The index levels */ }; /* ** Mark a section of the memory block as in-use. */ static void useSpace(MemPage *pPage, int start, int size){ int i; FreeBlk *p; /* Some basic sanity checking */ assert( pPage && pPage->isInit ); assert( pPage->nFree>0 && pPage->nFree<=MX_FREE ); assert( pPage->nFreeSlot >= size ); assert( start > pPage->idxStart ); assert( size>0 ); assert( start + size < SQLITE_PAGE_SIZE/sizeof(pPage->aPage[0]) ); /* Search for the freeblock that describes the space to be used */ for(i=0; i<pPage->nFree; i++){ p = &pPage->aFree[i] if( p->idx<=start && p->idx+p->size>start ) break; } /* The freeblock must contain all the space that is to be used */ assert( i<pPage->nFree ); assert( p->idx+p->size >= start+size ); /* Remove the used space from the freeblock */ if( p->idx==start ){ /* The space is at the beginning of the block p->size -= size; if( p->size==0 ){ *p = pPage->aFree[pPage->nFree-1]; pPage->nFree--; } }else if( p->idx+p->size==start+size ){ /* Space at the end of the block */ p->size -= size; }else{ /* Space in the middle of the freeblock. */ FreeBlk *pNew; assert( p->nFreeSlot < MX_FREE ); pNew->idx = start+size; pNew->size = p->idx+p->size - pNew->idx; p->size = start - p->idx; } pPage->nFreeSlot -= size; } /* ** Return a section of the MemPage.aPage[] to the freelist. */ static void freeSpace(MemPage *pPage, int start, int size){ int end = start+size; int i; FreeBlk *pMatch = 0; FreeBlk * for(i=0; i<pPage->nFreeSlot; i++){ FreeBlk *p = &pPage->aFree[i]; if( p->idx==end+1 ){ if( pMatch ){ }else{ p->idx = start; p->size += size; pMatch = p; } } if( p->idx+p->size+1==start ){ p->size += size; break; } } } /* ** Defragment the freespace */ static void defragmentSpace(MemPage *pPage){ } /* ** Initialize the auxiliary information for a disk block. */ static int initPage(MemPage *pPage, Pgno pgnoThis, Pgno pgnoParent){ u32 idx; |
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** Boston, MA 02111-1307, USA. ** ** Author contact information: ** drh@hwaci.com ** http://www.hwaci.com/drh/ ** ************************************************************************* ** $Id: btree.c,v 1.4 2001/05/11 11:02:47 drh Exp $ */ #include "sqliteInt.h" #include "pager.h" #include "btree.h" #include <assert.h> typedef unsigned int u32; typedef unsigned short int u16; /* ** Forward declarations of structures used only in this file. */ typedef struct Page1Header Page1Header; typedef struct PageHdr PageHdr; typedef struct Cell Cell; typedef struct FreeBlk FreeBlk; /* ** The first page contains the following additional information: ** ** MAGIC-1 ** MAGIC-2 ** First free block */ #define EXTRA_PAGE_1_CELLS 3 #define MAGIC_1 0x7264dc61 #define MAGIC_2 0x54e55d9e struct Page1Header { u32 magic1; u32 magic2; Pgno firstList; }; /* ** Each database page has a header as follows: ** ** page1_header Extra numbers found on page 1 only. ** leftmost_pgno Page number of the leftmost child ** first_cell Index into MemPage.aPage of first cell ................................................................................ ** MemPage.pStart always points to the leftmost_pgno. First_free is ** 0 if there is no free space on this page. Otherwise it points to ** an area like this: ** ** nByte Number of free bytes in this block ** next_free Next free block or 0 if this is the end */ struct PageHdr { Pgno pgno; /* Child page that comes after all cells on this page */ u16 firstCell; /* Index in MemPage.aPage[] of the first cell */ u16 firstFree; /* Index in MemPage.aPage[] of the first free block */ }; struct Cell { Pgno pgno; /* Child page that comes before this cell */ u16 nKey; /* Number of bytes in the key */ u16 iNext; /* Index in MemPage.aPage[] of next cell in sorted order */ u32 nData; /* Number of bytes of data */ char aData[4]; /* Key and data */ }; struct FreeBlk { u16 iSize; /* Number of u32-sized slots in the block of free space */ u16 iNext; /* Index in MemPage.aPage[] of the next free block */ }; /* ** The maximum number of database entries that can be held in a single ** page of the database. Each entry has a 16-byte header consisting of ** 4 unsigned 32-bit numbers, as follows: ** ** nKey Number of byte in the key ................................................................................ ** next index in MemPage.aPage[] of the next entry in sorted order ** ** The key and data follow this header. The key and data are packed together ** and the total rounded up to the next multiple of 4 bytes. There must ** be at least 4 bytes in the key/data packet, so each entry consumes at ** least 20 bytes of space on the page. */ #define MX_CELL ((SQLITE_PAGE_SIZE-sizeof(PageHdr))/sizeof(Cell)) /* ** The maximum amount of data (in bytes) that can be stored locally for a ** database entry. If the entry contains more data than this, the ** extra goes onto overflow pages. */ #define MX_LOCAL_PAYLOAD ((SQLITE_PAGE_SIZE-20-4*24)/4) ................................................................................ unsigned char validUp; /* True if MemPage.up is valid */ unsigned char validLeft; /* True if MemPage.left is valid */ unsigned char validRight; /* True if MemPage.right is valid */ Pgno up; /* The parent page. 0 means this is the root */ Pgno left; /* Left sibling page. 0==none */ Pgno right; /* Right sibling page. 0==none */ int idxStart; /* Index in aPage[] of real data */ int nFree; /* Number of free slots of aPage[] */ int nCell; /* Number of entries on this page */ u32 *aCell[MX_CELL]; /* All entires in sorted order */ } typedef struct MemPage; /* ** The in-memory image of a disk page has the auxiliary information appended ................................................................................ Pager *pPager; /* The page cache */ BtCursor *pCursor; /* All open cursors */ MemPage *page1; /* First page of the database */ int inTrans; /* True if a transaction is current */ }; typedef Btree Bt; /* ** A cursor is a pointer to a particular entry in the BTree. ** The entry is identified by its MemPage and the index in ** MemPage.aCell[] of the entry. */ struct Cursor { Btree *pBt; /* The pointer back to the BTree */ MemPage *pPage; /* Page that contains the entry */ int idx; /* Index of the entry in pPage->aCell[] */ int skip_incr; /* */ }; /* ** The maximum depth of a cursor */ #define MX_LEVEL 20 /* ................................................................................ BtCursor *pPrev, *pNext; /* Linked list of all cursors */ int valid; /* True if the cursor points to something */ int nLevel; /* Number of levels of indexing used */ BtIdxpt *pLevel; /* Pointer to aLevel[nLevel] */ BtIdxpt aLevel[MX_LEVEL]; /* The index levels */ }; /* ** Defragment the page given. All of the free space ** is collected into one big block at the end of the ** page. */ static void defragmentPage(MemPage *pPage){ } /* ** Mark a section of the memory block as in-use. */ static void useSpace(MemPage *pPage, int start, int size){ } /* ** Return a section of the MemPage.aPage[] to the freelist. */ static void freeSpace(MemPage *pPage, int start, int size){ } /* ** Initialize the auxiliary information for a disk block. */ static int initPage(MemPage *pPage, Pgno pgnoThis, Pgno pgnoParent){ u32 idx; |