internal void ptrmapPut(Pgno key, PTRMAP eType, Pgno parent, ref RC rRC)
{
if (rRC != RC.OK)
{
return;
}
Debug.Assert(MutexEx.Held(this.Mutex));
// The master-journal page number must never be used as a pointer map page
Debug.Assert(!MemPage.PTRMAP_ISPAGE(this, MemPage.PENDING_BYTE_PAGE(this)));
Debug.Assert(this.AutoVacuum);
if (key == 0)
{
rRC = SysEx.SQLITE_CORRUPT_BKPT();
return;
}
var iPtrmap = MemPage.PTRMAP_PAGENO(this, key);
var pDbPage = new PgHdr(); // The pointer map page
var rc = this.Pager.Get(iPtrmap, ref pDbPage);
if (rc != RC.OK)
{
rRC = rc;
return;
}
var offset = (int)MemPage.PTRMAP_PTROFFSET(iPtrmap, key);
if (offset < 0)
{
rRC = SysEx.SQLITE_CORRUPT_BKPT();
goto ptrmap_exit;
}
Debug.Assert(offset <= (int)this.UsableSize - 5);
var pPtrmap = Pager.sqlite3PagerGetData(pDbPage); // The pointer map data
if (eType != (PTRMAP)pPtrmap[offset] || ConvertEx.Get4(pPtrmap, offset + 1) != parent)
{
Btree.TRACE("PTRMAP_UPDATE: {0}->({1},{2})", key, eType, parent);
rRC = rc = Pager.Write(pDbPage);
if (rc == RC.OK)
{
pPtrmap[offset] = (byte)eType;
ConvertEx.Put4L(pPtrmap, (uint)offset + 1, parent);
}
}
ptrmap_exit:
Pager.Unref(pDbPage);
}
internal static RC balance_deeper(MemPage pRoot, ref MemPage ppChild)
{
MemPage pChild = null; // Pointer to a new child page
Pgno pgnoChild = 0; // Page number of the new child page
var pBt = pRoot.Shared;
Debug.Assert(pRoot.NOverflows > 0);
Debug.Assert(MutexEx.Held(pBt.Mutex));
// Make pRoot, the root page of the b-tree, writable. Allocate a new page that will become the new right-child of pPage. Copy the contents
// of the node stored on pRoot into the new child page.
var rc = Pager.Write(pRoot.DbPage);
if (rc == RC.OK)
{
rc = pBt.allocateBtreePage(ref pChild, ref pgnoChild, pRoot.ID, 0);
copyNodeContent(pRoot, pChild, ref rc);
#if !SQLITE_OMIT_AUTOVACUUM
if (pBt.AutoVacuum)
#else
if (false)
#endif
{
pBt.ptrmapPut(pgnoChild, PTRMAP.BTREE, pRoot.ID, ref rc);
}
}
if (rc != RC.OK)
{
ppChild = null;
pChild.releasePage();
return(rc);
}
Debug.Assert(Pager.IsPageWriteable(pChild.DbPage));
Debug.Assert(Pager.IsPageWriteable(pRoot.DbPage));
Debug.Assert(pChild.Cells == pRoot.Cells);
Btree.TRACE("BALANCE: copy root %d into %d\n", pRoot.ID, pChild.ID);
// Copy the overflow cells from pRoot to pChild
Array.Copy(pRoot.Overflows, pChild.Overflows, pRoot.NOverflows);
pChild.NOverflows = pRoot.NOverflows;
// Zero the contents of pRoot. Then install pChild as the right-child.
pRoot.zeroPage(pChild.Data[0] & ~Btree.PTF_LEAF);
ConvertEx.Put4L(pRoot.Data, pRoot.HeaderOffset + 8, pgnoChild);
ppChild = pChild;
return(RC.OK);
}
internal static RC balance_nonroot(MemPage pParent, int iParentIdx, byte[] aOvflSpace, int isRoot)
{
var apOld = new MemPage[NB]; // pPage and up to two siblings
var apCopy = new MemPage[NB]; // Private copies of apOld[] pages
var apNew = new MemPage[NB + 2]; // pPage and up to NB siblings after balancing
var apDiv = new int[NB - 1]; // Divider cells in pParent
var cntNew = new int[NB + 2]; // Index in aCell[] of cell after i-th page
var szNew = new int[NB + 2]; // Combined size of cells place on i-th page
var szCell = new ushort[1]; // Local size of all cells in apCell[]
BtShared pBt; // The whole database
int nCell = 0; // Number of cells in apCell[]
int nMaxCells = 0; // Allocated size of apCell, szCell, aFrom.
int nNew = 0; // Number of pages in apNew[]
ushort leafCorrection; // 4 if pPage is a leaf. 0 if not
int leafData; // True if pPage is a leaf of a LEAFDATA tree
int usableSpace; // Bytes in pPage beyond the header
int pageFlags; // Value of pPage.aData[0]
int subtotal; // Subtotal of bytes in cells on one page
int iOvflSpace = 0; // First unused byte of aOvflSpace[]
//int szScratch; // Size of scratch memory requested
byte[][] apCell = null; // All cells begin balanced
//
pBt = pParent.Shared;
Debug.Assert(MutexEx.Held(pBt.Mutex));
Debug.Assert(Pager.IsPageWriteable(pParent.DbPage));
#if false
Btree.TRACE("BALANCE: begin page %d child of %d\n", pPage.pgno, pParent.pgno);
#endif
// At this point pParent may have at most one overflow cell. And if this overflow cell is present, it must be the cell with
// index iParentIdx. This scenario comes about when this function is called (indirectly) from sqlite3BtreeDelete().
Debug.Assert(pParent.NOverflows == 0 || pParent.NOverflows == 1);
Debug.Assert(pParent.NOverflows == 0 || pParent.Overflows[0].Index == iParentIdx);
// Find the sibling pages to balance. Also locate the cells in pParent that divide the siblings. An attempt is made to find NN siblings on
// either side of pPage. More siblings are taken from one side, however, if there are fewer than NN siblings on the other side. If pParent
// has NB or fewer children then all children of pParent are taken.
// This loop also drops the divider cells from the parent page. This way, the remainder of the function does not have to deal with any
// overflow cells in the parent page, since if any existed they will have already been removed.
int nOld; // Number of pages in apOld[]
int nxDiv; // Next divider slot in pParent.aCell[]
var i = pParent.NOverflows + pParent.Cells;
if (i < 2)
{
nxDiv = 0;
nOld = i + 1;
}
else
{
nOld = 3;
if (iParentIdx == 0)
{
nxDiv = 0;
}
else if (iParentIdx == i)
{
nxDiv = i - 2;
}
else
{
nxDiv = iParentIdx - 1;
}
i = 2;
}
var pRight = ((i + nxDiv - pParent.NOverflows) == pParent.Cells ? pParent.HeaderOffset + 8 : pParent.FindCell(i + nxDiv - pParent.NOverflows)); // Location in parent of right-sibling pointer
var pgno = (Pgno)ConvertEx.Get4(pParent.Data, pRight);
var rc = RC.OK;
while (true)
{
rc = pBt.getAndInitPage(pgno, ref apOld[i]);
if (rc != RC.OK)
{
goto balance_cleanup;
}
nMaxCells += 1 + apOld[i].Cells + apOld[i].NOverflows;
if (i-- == 0)
{
break;
}
if (i + nxDiv == pParent.Overflows[0].Index && pParent.NOverflows != 0)
{
apDiv[i] = 0;
pgno = ConvertEx.Get4(pParent.Overflows[0].Cell, apDiv[i]);
szNew[i] = pParent.cellSizePtr(apDiv[i]);
pParent.NOverflows = 0;
}
else
{
apDiv[i] = pParent.FindCell(i + nxDiv - pParent.NOverflows);
pgno = ConvertEx.Get4(pParent.Data, apDiv[i]);
szNew[i] = pParent.cellSizePtr(apDiv[i]);
// Drop the cell from the parent page. apDiv[i] still points to the cell within the parent, even though it has been dropped.
// This is safe because dropping a cell only overwrites the first four bytes of it, and this function does not need the first
// four bytes of the divider cell. So the pointer is safe to use later on.
//
// Unless SQLite is compiled in secure-delete mode. In this case, the dropCell() routine will overwrite the entire cell with zeroes.
// In this case, temporarily copy the cell into the aOvflSpace[] buffer. It will be copied out again as soon as the aSpace[] buffer
// is allocated.
//if (pBt.secureDelete)
//{
// int iOff = (int)(apDiv[i]) - (int)(pParent.aData); //SQLITE_PTR_TO_INT(apDiv[i]) - SQLITE_PTR_TO_INT(pParent.aData);
// if( (iOff+szNew[i])>(int)pBt->usableSize )
// {
// rc = SQLITE_CORRUPT_BKPT();
// Array.Clear(apOld[0].aData,0,apOld[0].aData.Length); //memset(apOld, 0, (i + 1) * sizeof(MemPage*));
// goto balance_cleanup;
// }
// else
// {
// memcpy(&aOvflSpace[iOff], apDiv[i], szNew[i]);
// apDiv[i] = &aOvflSpace[apDiv[i] - pParent.aData];
// }
//}
pParent.dropCell(i + nxDiv - pParent.NOverflows, szNew[i], ref rc);
}
}
// Make nMaxCells a multiple of 4 in order to preserve 8-byte alignment
nMaxCells = (nMaxCells + 3) & ~3;
// Allocate space for memory structures
apCell = MallocEx.sqlite3ScratchMalloc(apCell, nMaxCells);
if (szCell.Length < nMaxCells)
{
Array.Resize(ref szCell, nMaxCells);
}
// Load pointers to all cells on sibling pages and the divider cells into the local apCell[] array. Make copies of the divider cells
// into space obtained from aSpace1[] and remove the the divider Cells from pParent.
// If the siblings are on leaf pages, then the child pointers of the divider cells are stripped from the cells before they are copied
// into aSpace1[]. In this way, all cells in apCell[] are without child pointers. If siblings are not leaves, then all cell in
// apCell[] include child pointers. Either way, all cells in apCell[] are alike.
// leafCorrection: 4 if pPage is a leaf. 0 if pPage is not a leaf.
// leafData: 1 if pPage holds key+data and pParent holds only keys.
leafCorrection = (ushort)(apOld[0].Leaf * 4);
leafData = apOld[0].HasData;
int j;
for (i = 0; i < nOld; i++)
{
// Before doing anything else, take a copy of the i'th original sibling The rest of this function will use data from the copies rather
// that the original pages since the original pages will be in the process of being overwritten.
var pOld = apCopy[i] = apOld[i].Clone();
var limit = pOld.Cells + pOld.NOverflows;
if (pOld.NOverflows > 0 || true)
{
for (j = 0; j < limit; j++)
{
Debug.Assert(nCell < nMaxCells);
var iFOFC = pOld.FindOverflowCell(j);
szCell[nCell] = pOld.cellSizePtr(iFOFC);
// Copy the Data Locally
if (apCell[nCell] == null)
{
apCell[nCell] = new byte[szCell[nCell]];
}
else if (apCell[nCell].Length < szCell[nCell])
{
Array.Resize(ref apCell[nCell], szCell[nCell]);
}
if (iFOFC < 0) // Overflow Cell
{
Buffer.BlockCopy(pOld.Overflows[-(iFOFC + 1)].Cell, 0, apCell[nCell], 0, szCell[nCell]);
}
else
{
Buffer.BlockCopy(pOld.Data, iFOFC, apCell[nCell], 0, szCell[nCell]);
}
nCell++;
}
}
else
{
var aData = pOld.Data;
var maskPage = pOld.MaskPage;
var cellOffset = pOld.CellOffset;
for (j = 0; j < limit; j++)
{
Debugger.Break();
Debug.Assert(nCell < nMaxCells);
apCell[nCell] = FindCellv2(aData, maskPage, cellOffset, j);
szCell[nCell] = pOld.cellSizePtr(apCell[nCell]);
nCell++;
}
}
if (i < nOld - 1 && 0 == leafData)
{
var sz = (ushort)szNew[i];
var pTemp = MallocEx.sqlite3Malloc(sz + leafCorrection);
Debug.Assert(nCell < nMaxCells);
szCell[nCell] = sz;
Debug.Assert(sz <= pBt.MaxLocal + 23);
Buffer.BlockCopy(pParent.Data, apDiv[i], pTemp, 0, sz);
if (apCell[nCell] == null || apCell[nCell].Length < sz)
{
Array.Resize(ref apCell[nCell], sz);
}
Buffer.BlockCopy(pTemp, leafCorrection, apCell[nCell], 0, sz);
Debug.Assert(leafCorrection == 0 || leafCorrection == 4);
szCell[nCell] = (ushort)(szCell[nCell] - leafCorrection);
if (0 == pOld.Leaf)
{
Debug.Assert(leafCorrection == 0);
Debug.Assert(pOld.HeaderOffset == 0);
// The right pointer of the child page pOld becomes the left pointer of the divider cell
Buffer.BlockCopy(pOld.Data, 8, apCell[nCell], 0, 4);//memcpy( apCell[nCell], ref pOld.aData[8], 4 );
}
else
{
Debug.Assert(leafCorrection == 4);
if (szCell[nCell] < 4)
{
// Do not allow any cells smaller than 4 bytes.
szCell[nCell] = 4;
}
}
nCell++;
}
}
// Figure out the number of pages needed to hold all nCell cells. Store this number in "k". Also compute szNew[] which is the total
// size of all cells on the i-th page and cntNew[] which is the index in apCell[] of the cell that divides page i from page i+1.
// cntNew[k] should equal nCell.
// Values computed by this block:
// k: The total number of sibling pages
// szNew[i]: Spaced used on the i-th sibling page.
// cntNew[i]: Index in apCell[] and szCell[] for the first cell to
// the right of the i-th sibling page.
// usableSpace: Number of bytes of space available on each sibling.
usableSpace = (int)pBt.UsableSize - 12 + leafCorrection;
int k;
for (subtotal = k = i = 0; i < nCell; i++)
{
Debug.Assert(i < nMaxCells);
subtotal += szCell[i] + 2;
if (subtotal > usableSpace)
{
szNew[k] = subtotal - szCell[i];
cntNew[k] = i;
if (leafData != 0)
{
i--;
}
subtotal = 0;
k++;
if (k > NB + 1)
{
rc = SysEx.SQLITE_CORRUPT_BKPT();
goto balance_cleanup;
}
}
}
szNew[k] = subtotal;
cntNew[k] = nCell;
k++;
// The packing computed by the previous block is biased toward the siblings on the left side. The left siblings are always nearly full, while the
// right-most sibling might be nearly empty. This block of code attempts to adjust the packing of siblings to get a better balance.
//
// This adjustment is more than an optimization. The packing above might be so out of balance as to be illegal. For example, the right-most
// sibling might be completely empty. This adjustment is not optional.
for (i = k - 1; i > 0; i--)
{
var szRight = szNew[i]; // Size of sibling on the right
var szLeft = szNew[i - 1]; // Size of sibling on the left
var r = cntNew[i - 1] - 1; // Index of right-most cell in left sibling
var d = r + 1 - leafData; // Index of first cell to the left of right sibling
Debug.Assert(d < nMaxCells);
Debug.Assert(r < nMaxCells);
while (szRight == 0 || szRight + szCell[d] + 2 <= szLeft - (szCell[r] + 2))
{
szRight += szCell[d] + 2;
szLeft -= szCell[r] + 2;
cntNew[i - 1]--;
r = cntNew[i - 1] - 1;
d = r + 1 - leafData;
}
szNew[i] = szRight;
szNew[i - 1] = szLeft;
}
// Either we found one or more cells (cntnew[0])>0) or pPage is a virtual root page. A virtual root page is when the real root
// page is page 1 and we are the only child of that page.
Debug.Assert(cntNew[0] > 0 || (pParent.ID == 1 && pParent.Cells == 0));
Btree.TRACE("BALANCE: old: %d %d %d ", apOld[0].ID, (nOld >= 2 ? apOld[1].ID : 0), (nOld >= 3 ? apOld[2].ID : 0));
// Allocate k new pages. Reuse old pages where possible.
if (apOld[0].ID <= 1)
{
rc = SysEx.SQLITE_CORRUPT_BKPT();
goto balance_cleanup;
}
pageFlags = apOld[0].Data[0];
for (i = 0; i < k; i++)
{
var pNew = new MemPage();
if (i < nOld)
{
pNew = apNew[i] = apOld[i];
apOld[i] = null;
rc = Pager.Write(pNew.DbPage);
nNew++;
if (rc != RC.OK)
{
goto balance_cleanup;
}
}
else
{
Debug.Assert(i > 0);
rc = pBt.allocateBtreePage(ref pNew, ref pgno, pgno, 0);
if (rc != 0)
{
goto balance_cleanup;
}
apNew[i] = pNew;
nNew++;
// Set the pointer-map entry for the new sibling page.
#if !SQLITE_OMIT_AUTOVACUUM
if (pBt.AutoVacuum)
#else
if (false)
#endif
{
pBt.ptrmapPut(pNew.ID, PTRMAP.BTREE, pParent.ID, ref rc);
if (rc != RC.OK)
{
goto balance_cleanup;
}
}
}
}
// Free any old pages that were not reused as new pages.
while (i < nOld)
{
apOld[i].freePage(ref rc);
if (rc != RC.OK)
{
goto balance_cleanup;
}
apOld[i].releasePage();
apOld[i] = null;
i++;
}
// Put the new pages in accending order. This helps to keep entries in the disk file in order so that a scan
// of the table is a linear scan through the file. That in turn helps the operating system to deliver pages
// from the disk more rapidly.
// An O(n^2) insertion sort algorithm is used, but since n is never more than NB (a small constant), that should
// not be a problem.
// When NB==3, this one optimization makes the database about 25% faster for large insertions and deletions.
for (i = 0; i < k - 1; i++)
{
var minV = (int)apNew[i].ID;
var minI = i;
for (j = i + 1; j < k; j++)
{
if (apNew[j].ID < (uint)minV)
{
minI = j;
minV = (int)apNew[j].ID;
}
}
if (minI > i)
{
var pT = apNew[i];
apNew[i] = apNew[minI];
apNew[minI] = pT;
}
}
Btree.TRACE("new: %d(%d) %d(%d) %d(%d) %d(%d) %d(%d)\n", apNew[0].ID, szNew[0],
(nNew >= 2 ? apNew[1].ID : 0), (nNew >= 2 ? szNew[1] : 0),
(nNew >= 3 ? apNew[2].ID : 0), (nNew >= 3 ? szNew[2] : 0),
(nNew >= 4 ? apNew[3].ID : 0), (nNew >= 4 ? szNew[3] : 0),
(nNew >= 5 ? apNew[4].ID : 0), (nNew >= 5 ? szNew[4] : 0));
Debug.Assert(Pager.IsPageWriteable(pParent.DbPage));
ConvertEx.Put4L(pParent.Data, pRight, apNew[nNew - 1].ID);
// Evenly distribute the data in apCell[] across the new pages. Insert divider cells into pParent as necessary.
j = 0;
for (i = 0; i < nNew; i++)
{
// Assemble the new sibling page.
MemPage pNew = apNew[i];
Debug.Assert(j < nMaxCells);
pNew.zeroPage(pageFlags);
pNew.assemblePage(cntNew[i] - j, apCell, szCell, j);
Debug.Assert(pNew.Cells > 0 || (nNew == 1 && cntNew[0] == 0));
Debug.Assert(pNew.NOverflows == 0);
j = cntNew[i];
// If the sibling page assembled above was not the right-most sibling, insert a divider cell into the parent page.
Debug.Assert(i < nNew - 1 || j == nCell);
if (j < nCell)
{
Debug.Assert(j < nMaxCells);
var pCell = apCell[j];
var sz = szCell[j] + leafCorrection;
var pTemp = MallocEx.sqlite3Malloc(sz);
if (pNew.Leaf == 0)
{
Buffer.BlockCopy(pCell, 0, pNew.Data, 8, 4);
}
else if (leafData != 0)
{
// If the tree is a leaf-data tree, and the siblings are leaves, then there is no divider cell in apCell[]. Instead, the divider
// cell consists of the integer key for the right-most cell of the sibling-page assembled above only.
var info = new CellInfo();
j--;
pNew.btreeParseCellPtr(apCell[j], ref info);
pCell = pTemp;
sz = 4 + ConvertEx.PutVarint9L(pCell, 4, (ulong)info.nKey);
pTemp = null;
}
else
{
//------------ pCell -= 4;
var _pCell_4 = MallocEx.sqlite3Malloc(pCell.Length + 4);
Buffer.BlockCopy(pCell, 0, _pCell_4, 4, pCell.Length);
pCell = _pCell_4;
// Obscure case for non-leaf-data trees: If the cell at pCell was previously stored on a leaf node, and its reported size was 4
// bytes, then it may actually be smaller than this (see btreeParseCellPtr(), 4 bytes is the minimum size of
// any cell). But it is important to pass the correct size to insertCell(), so reparse the cell now.
// Note that this can never happen in an SQLite data file, as all cells are at least 4 bytes. It only happens in b-trees used
// to evaluate "IN (SELECT ...)" and similar clauses.
if (szCell[j] == 4)
{
Debug.Assert(leafCorrection == 4);
sz = pParent.cellSizePtr(pCell);
}
}
iOvflSpace += sz;
Debug.Assert(sz <= pBt.MaxLocal + 23);
Debug.Assert(iOvflSpace <= (int)pBt.PageSize);
pParent.insertCell(nxDiv, pCell, sz, pTemp, pNew.ID, ref rc);
if (rc != RC.OK)
{
goto balance_cleanup;
}
Debug.Assert(Pager.IsPageWriteable(pParent.DbPage));
j++;
nxDiv++;
}
}
Debug.Assert(j == nCell);
Debug.Assert(nOld > 0);
Debug.Assert(nNew > 0);
if ((pageFlags & Btree.PTF_LEAF) == 0)
{
Buffer.BlockCopy(apCopy[nOld - 1].Data, 8, apNew[nNew - 1].Data, 8, 4);
}
if (isRoot != 0 && pParent.Cells == 0 && pParent.HeaderOffset <= apNew[0].FreeBytes)
{
// The root page of the b-tree now contains no cells. The only sibling page is the right-child of the parent. Copy the contents of the
// child page into the parent, decreasing the overall height of the b-tree structure by one. This is described as the "balance-shallower"
// sub-algorithm in some documentation.
// If this is an auto-vacuum database, the call to copyNodeContent() sets all pointer-map entries corresponding to database image pages
// for which the pointer is stored within the content being copied.
// The second Debug.Assert below verifies that the child page is defragmented (it must be, as it was just reconstructed using assemblePage()). This
// is important if the parent page happens to be page 1 of the database image. */
Debug.Assert(nNew == 1);
Debug.Assert(apNew[0].FreeBytes == (ConvertEx.Get2(apNew[0].Data, 5) - apNew[0].CellOffset - apNew[0].Cells * 2));
copyNodeContent(apNew[0], pParent, ref rc);
apNew[0].freePage(ref rc);
}
else
#if !SQLITE_OMIT_AUTOVACUUM
if (pBt.AutoVacuum)
#else
if (false)
#endif
{
// Fix the pointer-map entries for all the cells that were shifted around. There are several different types of pointer-map entries that need to
// be dealt with by this routine. Some of these have been set already, but many have not. The following is a summary:
// 1) The entries associated with new sibling pages that were not siblings when this function was called. These have already
// been set. We don't need to worry about old siblings that were moved to the free-list - the freePage() code has taken care
// of those.
// 2) The pointer-map entries associated with the first overflow page in any overflow chains used by new divider cells. These
// have also already been taken care of by the insertCell() code.
// 3) If the sibling pages are not leaves, then the child pages of cells stored on the sibling pages may need to be updated.
// 4) If the sibling pages are not internal intkey nodes, then any overflow pages used by these cells may need to be updated
// (internal intkey nodes never contain pointers to overflow pages).
// 5) If the sibling pages are not leaves, then the pointer-map entries for the right-child pages of each sibling may need
// to be updated.
// Cases 1 and 2 are dealt with above by other code. The next block deals with cases 3 and 4 and the one after that, case 5. Since
// setting a pointer map entry is a relatively expensive operation, this code only sets pointer map entries for child or overflow pages that have
// actually moved between pages.
var pNew = apNew[0];
var pOld = apCopy[0];
var nOverflow = pOld.NOverflows;
var iNextOld = pOld.Cells + nOverflow;
var iOverflow = (nOverflow != 0 ? pOld.Overflows[0].Index : -1);
j = 0; // Current 'old' sibling page
k = 0; // Current 'new' sibling page
for (i = 0; i < nCell; i++)
{
var isDivider = 0;
while (i == iNextOld)
{
// Cell i is the cell immediately following the last cell on old sibling page j. If the siblings are not leaf pages of an
// intkey b-tree, then cell i was a divider cell.
pOld = apCopy[++j];
iNextOld = i + (0 == leafData ? 1 : 0) + pOld.Cells + pOld.NOverflows;
if (pOld.NOverflows != 0)
{
nOverflow = pOld.NOverflows;
iOverflow = i + (0 == leafData ? 1 : 0) + pOld.Overflows[0].Index;
}
isDivider = 0 == leafData ? 1 : 0;
}
Debug.Assert(nOverflow > 0 || iOverflow < i);
Debug.Assert(nOverflow < 2 || pOld.Overflows[0].Index == pOld.Overflows[1].Index - 1);
Debug.Assert(nOverflow < 3 || pOld.Overflows[1].Index == pOld.Overflows[2].Index - 1);
if (i == iOverflow)
{
isDivider = 1;
if (--nOverflow > 0)
{
iOverflow++;
}
}
if (i == cntNew[k])
{
// Cell i is the cell immediately following the last cell on new sibling page k. If the siblings are not leaf pages of an
// intkey b-tree, then cell i is a divider cell.
pNew = apNew[++k];
if (leafData == 0)
{
continue;
}
}
Debug.Assert(j < nOld);
Debug.Assert(k < nNew);
// If the cell was originally divider cell (and is not now) or an overflow cell, or if the cell was located on a different sibling
// page before the balancing, then the pointer map entries associated with any child or overflow pages need to be updated.
if (isDivider != 0 || pOld.ID != pNew.ID)
{
if (leafCorrection == 0)
{
pBt.ptrmapPut(ConvertEx.Get4(apCell[i]), PTRMAP.BTREE, pNew.ID, ref rc);
}
if (szCell[i] > pNew.MinLocal)
{
pNew.ptrmapPutOvflPtr(apCell[i], ref rc);
}
}
}
if (leafCorrection == 0)
{
for (i = 0; i < nNew; i++)
{
var key = ConvertEx.Get4(apNew[i].Data, 8);
pBt.ptrmapPut(key, PTRMAP.BTREE, apNew[i].ID, ref rc);
}
}
#if false
// The ptrmapCheckPages() contains Debug.Assert() statements that verify that all pointer map pages are set correctly. This is helpful while
// debugging. This is usually disabled because a corrupt database may cause an Debug.Assert() statement to fail.
ptrmapCheckPages(apNew, nNew);
ptrmapCheckPages(pParent, 1);
#endif
}
Debug.Assert(pParent.HasInit);
Btree.TRACE("BALANCE: finished: old=%d new=%d cells=%d\n", nOld, nNew, nCell);
// Cleanup before returning.
balance_cleanup:
MallocEx.sqlite3ScratchFree(apCell);
for (i = 0; i < nOld; i++)
{
apOld[i].releasePage();
}
for (i = 0; i < nNew; i++)
{
apNew[i].releasePage();
}
return(rc);
}
internal RC freePage2(MemPage pMemPage, Pgno iPage)
{
MemPage pTrunk = null; // Free-list trunk page
var pPage1 = this.Page1; // Local reference to page 1
Debug.Assert(MutexEx.Held(this.Mutex));
Debug.Assert(iPage > 1);
Debug.Assert(pMemPage == null || pMemPage.ID == iPage);
MemPage pPage; // Page being freed. May be NULL.
if (pMemPage != null)
{
pPage = pMemPage;
Pager.AddPageRef(pPage.DbPage);
}
else
{
pPage = btreePageLookup(iPage);
}
// Increment the free page count on pPage1
var rc = Pager.Write(pPage1.DbPage);
if (rc != RC.OK)
{
goto freepage_out;
}
var nFree = (int)ConvertEx.Get4(pPage1.Data, 36); // Initial number of pages on free-list
ConvertEx.Put4(pPage1.Data, 36, nFree + 1);
if (this.SecureDelete)
{
// If the secure_delete option is enabled, then always fully overwrite deleted information with zeros.
if ((pPage == null && ((rc = btreeGetPage(iPage, ref pPage, 0)) != RC.OK)) || ((rc = Pager.Write(pPage.DbPage)) != RC.OK))
{
goto freepage_out;
}
Array.Clear(pPage.Data, 0, (int)pPage.Shared.PageSize);
}
// If the database supports auto-vacuum, write an entry in the pointer-map to indicate that the page is free.
#if !SQLITE_OMIT_AUTOVACUUM
if (this.AutoVacuum)
#else
if (false)
#endif
{
ptrmapPut(iPage, PTRMAP.FREEPAGE, 0, ref rc);
if (rc != RC.OK)
{
goto freepage_out;
}
}
// Now manipulate the actual database free-list structure. There are two possibilities. If the free-list is currently empty, or if the first
// trunk page in the free-list is full, then this page will become a new free-list trunk page. Otherwise, it will become a leaf of the
// first trunk page in the current free-list. This block tests if it is possible to add the page as a new free-list leaf.
Pgno iTrunk = 0; // Page number of free-list trunk page
if (nFree != 0)
{
uint nLeaf; // Initial number of leaf cells on trunk page
iTrunk = (Pgno)ConvertEx.Get4(pPage1.Data, 32); // Page number of free-list trunk page
rc = btreeGetPage(iTrunk, ref pTrunk, 0);
if (rc != RC.OK)
{
goto freepage_out;
}
nLeaf = ConvertEx.Get4(pTrunk.Data, 4);
Debug.Assert(this.UsableSize > 32);
if (nLeaf > (uint)this.UsableSize / 4 - 2)
{
rc = SysEx.SQLITE_CORRUPT_BKPT();
goto freepage_out;
}
if (nLeaf < (uint)this.UsableSize / 4 - 8)
{
// In this case there is room on the trunk page to insert the page being freed as a new leaf.
// Note: that the trunk page is not really full until it contains usableSize/4 - 2 entries, not usableSize/4 - 8 entries as we have
// coded. But due to a coding error in versions of SQLite prior to 3.6.0, databases with freelist trunk pages holding more than
// usableSize/4 - 8 entries will be reported as corrupt. In order to maintain backwards compatibility with older versions of SQLite,
// we will continue to restrict the number of entries to usableSize/4 - 8 for now. At some point in the future (once everyone has upgraded
// to 3.6.0 or later) we should consider fixing the conditional above to read "usableSize/4-2" instead of "usableSize/4-8".
rc = Pager.Write(pTrunk.DbPage);
if (rc == RC.OK)
{
ConvertEx.Put4(pTrunk.Data, 4, nLeaf + 1);
ConvertEx.Put4(pTrunk.Data, (uint)(8 + nLeaf * 4), iPage);
if (pPage != null && !this.SecureDelete)
{
Pager.DontWrite(pPage.DbPage);
}
rc = btreeSetHasContent(iPage);
}
Btree.TRACE("FREE-PAGE: %d leaf on trunk page %d\n", iPage, pTrunk.ID);
goto freepage_out;
}
}
// If control flows to this point, then it was not possible to add the the page being freed as a leaf page of the first trunk in the free-list.
// Possibly because the free-list is empty, or possibly because the first trunk in the free-list is full. Either way, the page being freed
// will become the new first trunk page in the free-list.
if (pPage == null && (rc = btreeGetPage(iPage, ref pPage, 0)) != RC.OK)
{
goto freepage_out;
}
rc = Pager.Write(pPage.DbPage);
if (rc != RC.OK)
{
goto freepage_out;
}
ConvertEx.Put4L(pPage.Data, iTrunk);
ConvertEx.Put4(pPage.Data, 4, 0);
ConvertEx.Put4(pPage1.Data, 32, iPage);
Btree.TRACE("FREE-PAGE: %d new trunk page replacing %d\n", pPage.ID, iTrunk);
freepage_out:
if (pPage != null)
{
pPage.HasInit = false;
}
pPage.releasePage();
pTrunk.releasePage();
return(rc);
}
internal RC allocateBtreePage(ref MemPage ppPage, ref Pgno pPgno, Pgno nearby, byte exact)
{
MemPage pTrunk = null;
MemPage pPrevTrunk = null;
Debug.Assert(MutexEx.Held(this.Mutex));
var pPage1 = this.Page1;
var mxPage = btreePagecount(); // Total size of the database file
var n = ConvertEx.Get4(pPage1.Data, 36); // Number of pages on the freelist
if (n >= mxPage)
{
return(SysEx.SQLITE_CORRUPT_BKPT());
}
RC rc;
if (n > 0)
{
// There are pages on the freelist. Reuse one of those pages.
Pgno iTrunk;
byte searchList = 0; // If the free-list must be searched for 'nearby'
// If the 'exact' parameter was true and a query of the pointer-map shows that the page 'nearby' is somewhere on the free-list, then the entire-list will be searched for that page.
#if !SQLITE_OMIT_AUTOVACUUM
if (exact != 0 && nearby <= mxPage)
{
Debug.Assert(nearby > 0);
Debug.Assert(this.AutoVacuum);
PTRMAP eType = 0;
uint dummy0 = 0;
rc = ptrmapGet(nearby, ref eType, ref dummy0);
if (rc != RC.OK)
{
return(rc);
}
if (eType == PTRMAP.FREEPAGE)
{
searchList = 1;
}
pPgno = nearby;
}
#endif
// Decrement the free-list count by 1. Set iTrunk to the index of the first free-list trunk page. iPrevTrunk is initially 1.
rc = Pager.Write(pPage1.DbPage);
if (rc != RC.OK)
{
return(rc);
}
ConvertEx.Put4(pPage1.Data, 36, n - 1);
// The code within this loop is run only once if the 'searchList' variable is not true. Otherwise, it runs once for each trunk-page on the
// free-list until the page 'nearby' is located.
do
{
pPrevTrunk = pTrunk;
iTrunk = (pPrevTrunk != null ? ConvertEx.Get4(pPrevTrunk.Data, 0) : ConvertEx.Get4(pPage1.Data, 32));
rc = (iTrunk > mxPage ? SysEx.SQLITE_CORRUPT_BKPT() : btreeGetPage(iTrunk, ref pTrunk, 0));
if (rc != RC.OK)
{
pTrunk = null;
goto end_allocate_page;
}
var k = ConvertEx.Get4(pTrunk.Data, 4); // # of leaves on this trunk page
if (k == 0 && searchList == 0)
{
// The trunk has no leaves and the list is not being searched. So extract the trunk page itself and use it as the newly allocated page
Debug.Assert(pPrevTrunk == null);
rc = Pager.Write(pTrunk.DbPage);
if (rc != RC.OK)
{
goto end_allocate_page;
}
pPgno = iTrunk;
Buffer.BlockCopy(pTrunk.Data, 0, pPage1.Data, 32, 4);
ppPage = pTrunk;
pTrunk = null;
Btree.TRACE("ALLOCATE: %d trunk - %d free pages left\n", pPgno, n - 1);
}
else if (k > (uint)(this.UsableSize / 4 - 2))
{
// Value of k is out of range. Database corruption
rc = SysEx.SQLITE_CORRUPT_BKPT();
goto end_allocate_page;
#if !SQLITE_OMIT_AUTOVACUUM
}
else if (searchList != 0 && nearby == iTrunk)
{
// The list is being searched and this trunk page is the page to allocate, regardless of whether it has leaves.
Debug.Assert(pPgno == iTrunk);
ppPage = pTrunk;
searchList = 0;
rc = Pager.Write(pTrunk.DbPage);
if (rc != RC.OK)
{
goto end_allocate_page;
}
if (k == 0)
{
if (pPrevTrunk == null)
{
pPage1.Data[32 + 0] = pTrunk.Data[0 + 0];
pPage1.Data[32 + 1] = pTrunk.Data[0 + 1];
pPage1.Data[32 + 2] = pTrunk.Data[0 + 2];
pPage1.Data[32 + 3] = pTrunk.Data[0 + 3];
}
else
{
rc = Pager.Write(pPrevTrunk.DbPage);
if (rc != RC.OK)
{
goto end_allocate_page;
}
pPrevTrunk.Data[0 + 0] = pTrunk.Data[0 + 0];
pPrevTrunk.Data[0 + 1] = pTrunk.Data[0 + 1];
pPrevTrunk.Data[0 + 2] = pTrunk.Data[0 + 2];
pPrevTrunk.Data[0 + 3] = pTrunk.Data[0 + 3];
}
}
else
{
// The trunk page is required by the caller but it contains pointers to free-list leaves. The first leaf becomes a trunk page in this case.
var pNewTrunk = new MemPage();
var iNewTrunk = (Pgno)ConvertEx.Get4(pTrunk.Data, 8);
if (iNewTrunk > mxPage)
{
rc = SysEx.SQLITE_CORRUPT_BKPT();
goto end_allocate_page;
}
rc = btreeGetPage(iNewTrunk, ref pNewTrunk, 0);
if (rc != RC.OK)
{
goto end_allocate_page;
}
rc = Pager.Write(pNewTrunk.DbPage);
if (rc != RC.OK)
{
pNewTrunk.releasePage();
goto end_allocate_page;
}
pNewTrunk.Data[0 + 0] = pTrunk.Data[0 + 0];
pNewTrunk.Data[0 + 1] = pTrunk.Data[0 + 1];
pNewTrunk.Data[0 + 2] = pTrunk.Data[0 + 2];
pNewTrunk.Data[0 + 3] = pTrunk.Data[0 + 3];
ConvertEx.Put4(pNewTrunk.Data, 4, (uint)(k - 1));
Buffer.BlockCopy(pTrunk.Data, 12, pNewTrunk.Data, 8, (int)(k - 1) * 4);
pNewTrunk.releasePage();
if (pPrevTrunk == null)
{
Debug.Assert(Pager.IsPageWriteable(pPage1.DbPage));
ConvertEx.Put4(pPage1.Data, 32, iNewTrunk);
}
else
{
rc = Pager.Write(pPrevTrunk.DbPage);
if (rc != RC.OK)
{
goto end_allocate_page;
}
ConvertEx.Put4(pPrevTrunk.Data, 0, iNewTrunk);
}
}
pTrunk = null;
Btree.TRACE("ALLOCATE: %d trunk - %d free pages left\n", pPgno, n - 1);
#endif
}
else if (k > 0)
{
// Extract a leaf from the trunk
uint closest;
var aData = pTrunk.Data;
if (nearby > 0)
{
closest = 0;
var dist = Math.Abs((int)(ConvertEx.Get4(aData, 8) - nearby));
for (uint i = 1; i < k; i++)
{
int dist2 = Math.Abs((int)(ConvertEx.Get4(aData, 8 + i * 4) - nearby));
if (dist2 < dist)
{
closest = i;
dist = dist2;
}
}
}
else
{
closest = 0;
}
//
var iPage = (Pgno)ConvertEx.Get4(aData, 8 + closest * 4);
if (iPage > mxPage)
{
rc = SysEx.SQLITE_CORRUPT_BKPT();
goto end_allocate_page;
}
if (searchList == 0 || iPage == nearby)
{
pPgno = iPage;
Btree.TRACE("ALLOCATE: %d was leaf %d of %d on trunk %d" + ": %d more free pages\n", pPgno, closest + 1, k, pTrunk.ID, n - 1);
rc = Pager.Write(pTrunk.DbPage);
if (rc != RC.OK)
{
goto end_allocate_page;
}
if (closest < k - 1)
{
Buffer.BlockCopy(aData, (int)(4 + k * 4), aData, 8 + (int)closest * 4, 4);
}
ConvertEx.Put4(aData, 4, (k - 1));
var noContent = (!btreeGetHasContent(pPgno) ? 1 : 0);
rc = btreeGetPage(pPgno, ref ppPage, noContent);
if (rc == RC.OK)
{
rc = Pager.Write((ppPage).DbPage);
if (rc != RC.OK)
{
ppPage.releasePage();
}
}
searchList = 0;
}
}
pPrevTrunk.releasePage();
pPrevTrunk = null;
} while (searchList != 0);
}
else
{
// There are no pages on the freelist, so create a new page at the end of the file
rc = Pager.Write(this.Page1.DbPage);
if (rc != RC.OK)
{
return(rc);
}
this.Pages++;
if (this.Pages == MemPage.PENDING_BYTE_PAGE(this))
{
this.Pages++;
}
#if !SQLITE_OMIT_AUTOVACUUM
if (this.AutoVacuum && MemPage.PTRMAP_ISPAGE(this, this.Pages))
{
// If pPgno refers to a pointer-map page, allocate two new pages at the end of the file instead of one. The first allocated page
// becomes a new pointer-map page, the second is used by the caller.
MemPage pPg = null;
Btree.TRACE("ALLOCATE: %d from end of file (pointer-map page)\n", pPgno);
Debug.Assert(this.Pages != MemPage.PENDING_BYTE_PAGE(this));
rc = btreeGetPage(this.Pages, ref pPg, 1);
if (rc == RC.OK)
{
rc = Pager.Write(pPg.DbPage);
pPg.releasePage();
}
if (rc != RC.OK)
{
return(rc);
}
this.Pages++;
if (this.Pages == MemPage.PENDING_BYTE_PAGE(this))
{
this.Pages++;
}
}
#endif
ConvertEx.Put4(this.Page1.Data, 28, this.Pages);
pPgno = this.Pages;
Debug.Assert(pPgno != MemPage.PENDING_BYTE_PAGE(this));
rc = btreeGetPage(pPgno, ref ppPage, 1);
if (rc != RC.OK)
{
return(rc);
}
rc = Pager.Write((ppPage).DbPage);
if (rc != RC.OK)
{
ppPage.releasePage();
}
Btree.TRACE("ALLOCATE: %d from end of file\n", pPgno);
}
Debug.Assert(pPgno != MemPage.PENDING_BYTE_PAGE(this));
end_allocate_page:
pTrunk.releasePage();
pPrevTrunk.releasePage();
if (rc == RC.OK)
{
if (Pager.GetPageRefCount((ppPage).DbPage) > 1)
{
ppPage.releasePage();
return(SysEx.SQLITE_CORRUPT_BKPT());
}
(ppPage).HasInit = false;
}
else
{
ppPage = null;
}
Debug.Assert(rc != RC.OK || Pager.IsPageWriteable((ppPage).DbPage));
return(rc);
}
internal static RC relocatePage(BtShared pBt, MemPage pDbPage, PTRMAP eType, Pgno iPtrPage, Pgno iFreePage, int isCommit)
{
var pPtrPage = new MemPage(); // The page that contains a pointer to pDbPage
var iDbPage = pDbPage.ID;
var pPager = pBt.Pager;
Debug.Assert(eType == PTRMAP.OVERFLOW2 || eType == PTRMAP.OVERFLOW1 || eType == PTRMAP.BTREE || eType == PTRMAP.ROOTPAGE);
Debug.Assert(MutexEx.Held(pBt.Mutex));
Debug.Assert(pDbPage.Shared == pBt);
// Move page iDbPage from its current location to page number iFreePage
Btree.TRACE("AUTOVACUUM: Moving %d to free page %d (ptr page %d type %d)\n", iDbPage, iFreePage, iPtrPage, eType);
var rc = pPager.sqlite3PagerMovepage(pDbPage.DbPage, iFreePage, isCommit);
if (rc != RC.OK)
{
return(rc);
}
pDbPage.ID = iFreePage;
// If pDbPage was a btree-page, then it may have child pages and/or cells that point to overflow pages. The pointer map entries for all these
// pages need to be changed.
// If pDbPage is an overflow page, then the first 4 bytes may store a pointer to a subsequent overflow page. If this is the case, then
// the pointer map needs to be updated for the subsequent overflow page.
if (eType == PTRMAP.BTREE || eType == PTRMAP.ROOTPAGE)
{
rc = pDbPage.setChildPtrmaps();
if (rc != RC.OK)
{
return(rc);
}
}
else
{
var nextOvfl = (Pgno)ConvertEx.Get4(pDbPage.Data);
if (nextOvfl != 0)
{
pBt.ptrmapPut(nextOvfl, PTRMAP.OVERFLOW2, iFreePage, ref rc);
if (rc != RC.OK)
{
return(rc);
}
}
}
// Fix the database pointer on page iPtrPage that pointed at iDbPage so that it points at iFreePage. Also fix the pointer map entry for iPtrPage.
if (eType != PTRMAP.ROOTPAGE)
{
rc = pBt.btreeGetPage(iPtrPage, ref pPtrPage, 0);
if (rc != RC.OK)
{
return(rc);
}
rc = Pager.Write(pPtrPage.DbPage);
if (rc != RC.OK)
{
pPtrPage.releasePage();
return(rc);
}
rc = pPtrPage.modifyPagePointer(iDbPage, iFreePage, eType);
pPtrPage.releasePage();
if (rc == RC.OK)
{
pBt.ptrmapPut(iFreePage, eType, iPtrPage, ref rc);
}
}
return(rc);
}
// was:sqlite3BtreeInsert
public RC Insert(byte[] key, long nKey, byte[] data, int nData, int nZero, bool appendBiasRight, int seekResult)
{
var loc = seekResult; // -1: before desired location +1: after
var szNew = 0;
int idx;
var p = this.Tree;
var pBt = p.Shared;
int oldCell;
byte[] newCell = null;
if (this.State == CursorState.FAULT)
{
Debug.Assert(this.SkipNext != 0);
return((RC)this.SkipNext);
}
Debug.Assert(HoldsMutex());
Debug.Assert(this.Writeable && pBt.InTransaction == TRANS.WRITE && !pBt.ReadOnly);
Debug.Assert(p.hasSharedCacheTableLock(this.RootID, (this.KeyInfo != null), LOCK.WRITE));
// Assert that the caller has been consistent. If this cursor was opened expecting an index b-tree, then the caller should be inserting blob
// keys with no associated data. If the cursor was opened expecting an intkey table, the caller should be inserting integer keys with a
// blob of associated data.
Debug.Assert((key == null) == (this.KeyInfo == null));
// If this is an insert into a table b-tree, invalidate any incrblob cursors open on the row being replaced (assuming this is a replace
// operation - if it is not, the following is a no-op). */
if (this.KeyInfo == null)
{
Btree.invalidateIncrblobCursors(p, nKey, false);
}
// Save the positions of any other cursors open on this table.
// In some cases, the call to btreeMoveto() below is a no-op. For example, when inserting data into a table with auto-generated integer
// keys, the VDBE layer invokes sqlite3BtreeLast() to figure out the integer key to use. It then calls this function to actually insert the
// data into the intkey B-Tree. In this case btreeMoveto() recognizes that the cursor is already where it needs to be and returns without
// doing any work. To avoid thwarting these optimizations, it is important not to clear the cursor here.
var rc = pBt.saveAllCursors(this.RootID, this);
if (rc != RC.OK)
{
return(rc);
}
if (loc == 0)
{
rc = BtreeMoveTo(key, nKey, appendBiasRight, ref loc);
if (rc != RC.OK)
{
return(rc);
}
}
Debug.Assert(this.State == CursorState.VALID || (this.State == CursorState.INVALID && loc != 0));
var pPage = this.Pages[this.PageID];
Debug.Assert(pPage.HasIntKey || nKey >= 0);
Debug.Assert(pPage.Leaf != 0 || !pPage.HasIntKey);
Btree.TRACE("INSERT: table=%d nkey=%lld ndata=%d page=%d %s\n", this.RootID, nKey, nData, pPage.ID, (loc == 0 ? "overwrite" : "new entry"));
Debug.Assert(pPage.HasInit);
pBt.allocateTempSpace();
newCell = pBt.pTmpSpace;
rc = pPage.fillInCell(newCell, key, nKey, data, nData, nZero, ref szNew);
if (rc != RC.OK)
{
goto end_insert;
}
Debug.Assert(szNew == pPage.cellSizePtr(newCell));
Debug.Assert(szNew <= Btree.MX_CELL_SIZE(pBt));
idx = this.PagesIndexs[this.PageID];
if (loc == 0)
{
ushort szOld;
Debug.Assert(idx < pPage.Cells);
rc = Pager.Write(pPage.DbPage);
if (rc != RC.OK)
{
goto end_insert;
}
oldCell = pPage.FindCell(idx);
if (0 == pPage.Leaf)
{
newCell[0] = pPage.Data[oldCell + 0];
newCell[1] = pPage.Data[oldCell + 1];
newCell[2] = pPage.Data[oldCell + 2];
newCell[3] = pPage.Data[oldCell + 3];
}
szOld = pPage.cellSizePtr(oldCell);
rc = pPage.clearCell(oldCell);
pPage.dropCell(idx, szOld, ref rc);
if (rc != RC.OK)
{
goto end_insert;
}
}
else if (loc < 0 && pPage.Cells > 0)
{
Debug.Assert(pPage.Leaf != 0);
idx = ++this.PagesIndexs[this.PageID];
}
else
{
Debug.Assert(pPage.Leaf != 0);
}
pPage.insertCell(idx, newCell, szNew, null, 0, ref rc);
Debug.Assert(rc != RC.OK || pPage.Cells > 0 || pPage.NOverflows > 0);
// If no error has occured and pPage has an overflow cell, call balance() to redistribute the cells within the tree. Since balance() may move
// the cursor, zero the BtCursor.info.nSize and BtCursor.validNKey variables.
// Previous versions of SQLite called moveToRoot() to move the cursor back to the root page as balance() used to invalidate the contents
// of BtCursor.apPage[] and BtCursor.aiIdx[]. Instead of doing that, set the cursor state to "invalid". This makes common insert operations
// slightly faster.
// There is a subtle but important optimization here too. When inserting multiple records into an intkey b-tree using a single cursor (as can
// happen while processing an "INSERT INTO ... SELECT" statement), it is advantageous to leave the cursor pointing to the last entry in
// the b-tree if possible. If the cursor is left pointing to the last entry in the table, and the next row inserted has an integer key
// larger than the largest existing key, it is possible to insert the row without seeking the cursor. This can be a big performance boost.
this.Info.nSize = 0;
this.ValidNKey = false;
if (rc == RC.OK && pPage.NOverflows != 0)
{
rc = Balance();
// Must make sure nOverflow is reset to zero even if the balance() fails. Internal data structure corruption will result otherwise.
// Also, set the cursor state to invalid. This stops saveCursorPosition() from trying to save the current position of the cursor.
this.Pages[this.PageID].NOverflows = 0;
this.State = CursorState.INVALID;
}
Debug.Assert(this.Pages[this.PageID].NOverflows == 0);
end_insert:
return(rc);
}