SQLite

/*
** 2005 July 8
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains code associated with the ANALYZE command.
**
** @(#) $Id: analyze.c,v 1.44 2008/11/03 20:55:07 drh Exp $
*/
#ifndef SQLITE_OMIT_ANALYZE
#include "sqliteInt.h"

/*
** This routine generates code that opens the sqlite_stat1 table on cursor
** iStatCur.

/*
** Generate code to do an analysis of all indices associated with
** a single table.
*/
static void analyzeOneTable(
  Parse *pParse,   /* Parser context */
  Table *pTab,     /* Table whose indices are to be analyzed */
  int iStatCur,    /* Index of VdbeCursor that writes the sqlite_stat1 table */
  int iMem         /* Available memory locations begin here */
){
  Index *pIdx;     /* An index to being analyzed */
  int iIdxCur;     /* Index of VdbeCursor for index being analyzed */
  int nCol;        /* Number of columns in the index */
  Vdbe *v;         /* The virtual machine being built up */
  int i;           /* Loop counter */
  int topOfLoop;   /* The top of the loop */
  int endOfLoop;   /* The end of the loop */
  int addr;        /* The address of an instruction */
  int iDb;         /* Index of database containing pTab */

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file implements an object that represents a fixed-length
** bitmap.  Bits are numbered starting with 1.
**
** A bitmap is used to record which pages of a database file have been
** journalled during a transaction, or which pages have the "dont-write"
** property.  Usually only a few pages are meet either condition.
** So the bitmap is usually sparse and has low cardinality.
** But sometimes (for example when during a DROP of a large table) most
** or all of the pages in a database can get journalled.  In those cases, 
** the bitmap becomes dense with high cardinality.  The algorithm needs 
** to handle both cases well.
**
** The size of the bitmap is fixed when the object is created.
**
** All bits are clear when the bitmap is created.  Individual bits
** may be set or cleared one at a time.
**
** Test operations are about 100 times more common that set operations.
** Clear operations are exceedingly rare.  There are usually between
** 5 and 500 set operations per Bitvec object, though the number of sets can
** sometimes grow into tens of thousands or larger.  The size of the
** Bitvec object is the number of pages in the database file at the
** start of a transaction, and is thus usually less than a few thousand,
** but can be as large as 2 billion for a really big database.
**
** @(#) $Id: bitvec.c,v 1.7 2008/11/03 20:55:07 drh Exp $
*/
#include "sqliteInt.h"

#define BITVEC_SZ        512
/* Round the union size down to the nearest pointer boundary, since that's how 
** it will be aligned within the Bitvec struct. */
#define BITVEC_USIZE     (((BITVEC_SZ-12)/sizeof(Bitvec*))*sizeof(Bitvec*))

    return 0;
  }
}

/*
** Set the i-th bit.  Return 0 on success and an error code if
** anything goes wrong.
**
** This routine might cause sub-bitmaps to be allocated.  Failing
** to get the memory needed to hold the sub-bitmap is the only
** that can go wrong with an insert, assuming p and i are valid.
**
** The calling function must ensure that p is a valid Bitvec object
** and that the value for "i" is within range of the Bitvec object.
** Otherwise the behavior is undefined.
*/
int sqlite3BitvecSet(Bitvec *p, u32 i){
  u32 h;
  assert( p!=0 );
  assert( i>0 );
  assert( i<=p->iSize );
  if( p->iSize<=BITVEC_NBIT ){

/*
** 2004 April 6
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.527 2008/11/03 20:55:07 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

#define restoreCursorPosition(p) \
  (p->eState>=CURSOR_REQUIRESEEK ? \
         sqlite3BtreeRestoreCursorPosition(p) : \
         SQLITE_OK)

/*
** Determine whether or not a cursor has moved from the position it
** was last placed at.  Cursors can move when the row they are pointing
** at is deleted out from under them.
**
** This routine returns an error code if something goes wrong.  The
** integer *pHasMoved is set to one if the cursor has moved and 0 if not.
*/
int sqlite3BtreeCursorHasMoved(BtCursor *pCur, int *pHasMoved){
  int rc;

**     CREATE INDEX
**     DROP INDEX
**     creating ID lists
**     BEGIN TRANSACTION
**     COMMIT
**     ROLLBACK
**
** $Id: build.c,v 1.500 2008/11/03 20:55:07 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** This routine is called when a new SQL statement is beginning to
** be parsed.  Initialize the pParse structure as needed.

  pItem->zDatabase = sqlite3NameFromToken(db, pDatabase);
  pItem->iCursor = -1;
  pList->nSrc++;
  return pList;
}

/*
** Assign VdbeCursor index numbers to all tables in a SrcList
*/
void sqlite3SrcListAssignCursors(Parse *pParse, SrcList *pList){
  int i;
  struct SrcList_item *pItem;
  assert(pList || pParse->db->mallocFailed );
  if( pList ){
    for(i=0, pItem=pList->a; i<pList->nSrc; i++, pItem++){

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle INSERT statements in SQLite.
**
** $Id: insert.c,v 1.251 2008/11/03 20:55:07 drh Exp $
*/
#include "sqliteInt.h"

/*
** Set P4 of the most recently inserted opcode to a column affinity
** string for index pIdx. A column affinity string has one character
** for each column in the table, according to the affinity of the column:

** for the table.  Indices are opened on subsequent cursors.
**
** Return the number of indices on the table.
*/
int sqlite3OpenTableAndIndices(
  Parse *pParse,   /* Parsing context */
  Table *pTab,     /* Table to be opened */
  int baseCur,     /* Cursor number assigned to the table */
  int op           /* OP_OpenRead or OP_OpenWrite */
){
  int i;
  int iDb;
  Index *pIdx;
  Vdbe *v;

** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.501 2008/11/03 20:55:07 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"

/*
** Macros for troubleshooting.  Normally turned off
*/

  return pPg->flags&PGHDR_DIRTY;
}
#endif

/*
** A call to this routine tells the pager that it is not necessary to
** write the information on page pPg back to the disk, even though
** that page might be marked as dirty.  This happens, for example, when
** the page has been added as a leaf of the freelist and so its
** content no longer matters.
**
** The overlying software layer calls this routine when all of the data
** on the given page is unused.  The pager marks the page as clean so
** that it does not get written to disk.
**
** Tests show that this optimization, together with the
** sqlite3PagerDontRollback() below, more than double the speed

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.785 2008/11/03 20:55:07 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
#include "vdbeInt.h"

/*
** The following global variable is incremented every time a cursor

*/
int sqlite3VdbeOpcodeHasProperty(int opcode, int mask){
  assert( opcode>0 && opcode<sizeof(opcodeProperty) );
  return (opcodeProperty[opcode]&mask)!=0;
}

/*
** Allocate VdbeCursor number iCur.  Return a pointer to it.  Return NULL
** if we run out of memory.
*/
static VdbeCursor *allocateCursor(
  Vdbe *p,              /* The virtual machine */
  int iCur,             /* Index of the new VdbeCursor */
  Op *pOp,              /* */
  int iDb,              /* */
  int isBtreeCursor     /* */
){
  /* Find the memory cell that will be used to store the blob of memory
  ** required for this VdbeCursor structure. It is convenient to use a 
  ** vdbe memory cell to manage the memory allocation required for a
  ** VdbeCursor structure for the following reasons:
  **
  **   * Sometimes cursor numbers are used for a couple of different
  **     purposes in a vdbe program. The different uses might require
  **     different sized allocations. Memory cells provide growable
  **     allocations.
  **
  **   * When using ENABLE_MEMORY_MANAGEMENT, memory cell buffers can
  **     be freed lazily via the sqlite3_release_memory() API. This
  **     minimizes the number of malloc calls made by the system.
  **
  ** Memory cells for cursors are allocated at the top of the address
  ** space. Memory cell (p->nMem) corresponds to cursor 0. Space for
  ** cursor 1 is managed by memory cell (p->nMem-1), etc.
  */
  Mem *pMem = &p->aMem[p->nMem-iCur];

  int nByte;
  VdbeCursor *pCx = 0;
  /* If the opcode of pOp is OP_SetNumColumns, then pOp->p2 contains
  ** the number of fields in the records contained in the table or
  ** index being opened. Use this to reserve space for the 
  ** VdbeCursor.aType[] array.
  */
  int nField = 0;
  if( pOp->opcode==OP_SetNumColumns || pOp->opcode==OP_OpenEphemeral ){
    nField = pOp->p2;
  }
  nByte = 
      sizeof(VdbeCursor) + 
      (isBtreeCursor?sqlite3BtreeCursorSize():0) + 
      2*nField*sizeof(u32);

  assert( iCur<p->nCursor );
  if( p->apCsr[iCur] ){
    sqlite3VdbeFreeCursor(p, p->apCsr[iCur]);
    p->apCsr[iCur] = 0;
  }
  if( SQLITE_OK==sqlite3VdbeMemGrow(pMem, nByte, 0) ){
    p->apCsr[iCur] = pCx = (VdbeCursor*)pMem->z;
    memset(pMem->z, 0, nByte);
    pCx->iDb = iDb;
    pCx->nField = nField;
    if( nField ){
      pCx->aType = (u32 *)&pMem->z[sizeof(VdbeCursor)];
    }
    if( isBtreeCursor ){
      pCx->pCursor = (BtCursor*)
          &pMem->z[sizeof(VdbeCursor)+2*nField*sizeof(u32)];
    }
  }
  return pCx;
}

/*
** Try to convert a value into a numeric representation if we can

** the MakeRecord instruction.  (See the MakeRecord opcode for additional
** information about the format of the data.)  Extract the P2-th column
** from this record.  If there are less that (P2+1) 
** values in the record, extract a NULL.
**
** The value extracted is stored in register P3.
**



** If the column contains fewer than P2 fields, then extract a NULL.  Or,
** if the P4 argument is a P4_MEM use the value of the P4 argument as
** the result.
*/
case OP_Column: {
  u32 payloadSize;   /* Number of bytes in the record */
  int p1 = pOp->p1;  /* P1 value of the opcode */
  int p2 = pOp->p2;  /* column number to retrieve */
  VdbeCursor *pC = 0;/* The VDBE cursor */
  char *zRec;        /* Pointer to complete record-data */
  BtCursor *pCrsr;   /* The BTree cursor */
  u32 *aType;        /* aType[i] holds the numeric type of the i-th column */
  u32 *aOffset;      /* aOffset[i] is offset to start of data for i-th column */
  u32 nField;        /* number of fields in the record */
  int len;           /* The length of the serialized data for the column */
  int i;             /* Loop counter */

  ** zRec is set to be the complete text of the record if it is available.
  ** The complete record text is always available for pseudo-tables
  ** If the record is stored in a cursor, the complete record text
  ** might be available in the  pC->aRow cache.  Or it might not be.
  ** If the data is unavailable,  zRec is set to NULL.
  **
  ** We also compute the number of columns in the record.  For cursors,
  ** the number of columns is stored in the VdbeCursor.nField element.
  */
  pC = p->apCsr[p1];
  assert( pC!=0 );
#ifndef SQLITE_OMIT_VIRTUALTABLE
  assert( pC->pVtabCursor==0 );
#endif
  if( pC->pCursor!=0 ){

case OP_OpenRead:
case OP_OpenWrite: {
  int i = pOp->p1;
  int p2 = pOp->p2;
  int iDb = pOp->p3;
  int wrFlag;
  Btree *pX;
  VdbeCursor *pCur;
  Db *pDb;
  
  assert( iDb>=0 && iDb<db->nDb );
  assert( (p->btreeMask & (1<<iDb))!=0 );
  pDb = &db->aDb[iDb];
  pX = pDb->pBt;
  assert( pX!=0 );

** confusion because the term "temp table", might refer either
** to a TEMP table at the SQL level, or to a table opened by
** this opcode.  Then this opcode was call OpenVirtual.  But
** that created confusion with the whole virtual-table idea.
*/
case OP_OpenEphemeral: {
  int i = pOp->p1;
  VdbeCursor *pCx;
  static const int openFlags = 
      SQLITE_OPEN_READWRITE |
      SQLITE_OPEN_CREATE |
      SQLITE_OPEN_EXCLUSIVE |
      SQLITE_OPEN_DELETEONCLOSE |
      SQLITE_OPEN_TRANSIENT_DB;

** original row data. Otherwise, a pointer to the original memory cell
** is stored. In this case, the vdbe program must ensure that the 
** memory cell containing the row data is not overwritten until the
** pseudo table is closed (or a new row is inserted into it).
*/
case OP_OpenPseudo: {
  int i = pOp->p1;
  VdbeCursor *pCx;
  assert( i>=0 );
  pCx = allocateCursor(p, i, &pOp[-1], -1, 0);
  if( pCx==0 ) goto no_mem;
  pCx->nullRow = 1;
  pCx->pseudoTable = 1;
  pCx->ephemPseudoTable = pOp->p2;
  pCx->isTable = 1;

** See also: Found, NotFound, Distinct, MoveGt, MoveGe, MoveLt
*/
case OP_MoveLt:         /* jump, in3 */
case OP_MoveLe:         /* jump, in3 */
case OP_MoveGe:         /* jump, in3 */
case OP_MoveGt: {       /* jump, in3 */
  int i = pOp->p1;
  VdbeCursor *pC;

  assert( i>=0 && i<p->nCursor );
  pC = p->apCsr[i];
  assert( pC!=0 );
  if( pC->pCursor!=0 ){
    int res, oc;
    oc = pOp->opcode;

**
** See also: Found, NotExists, IsUnique
*/
case OP_NotFound:       /* jump, in3 */
case OP_Found: {        /* jump, in3 */
  int i = pOp->p1;
  int alreadyExists = 0;
  VdbeCursor *pC;
  assert( i>=0 && i<p->nCursor );
  assert( p->apCsr[i]!=0 );
  if( (pC = p->apCsr[i])->pCursor!=0 ){
    int res;
    UnpackedRecord *pIdxKey;

    assert( pC->isTable==0 );

** number for that entry is written into P3 and control
** falls through to the next instruction.
**
** See also: NotFound, NotExists, Found
*/
case OP_IsUnique: {        /* jump, in3 */
  int i = pOp->p1;
  VdbeCursor *pCx;
  BtCursor *pCrsr;
  Mem *pK;
  i64 R;

  /* Pop the value R off the top of the stack
  */
  assert( pOp->p4type==P4_INT32 );

** NotFound assumes key is a blob constructed from MakeRecord and
** P1 is an index.
**
** See also: Found, NotFound, IsUnique
*/
case OP_NotExists: {        /* jump, in3 */
  int i = pOp->p1;
  VdbeCursor *pC;
  BtCursor *pCrsr;
  assert( i>=0 && i<p->nCursor );
  assert( p->apCsr[i]!=0 );
  if( (pCrsr = (pC = p->apCsr[i])->pCursor)!=0 ){
    int res;
    u64 iKey;
    assert( pIn3->flags & MEM_Int );

** error is generated.  The P3 register is updated with the generated
** record number.  This P3 mechanism is used to help implement the
** AUTOINCREMENT feature.
*/
case OP_NewRowid: {           /* out2-prerelease */
  int i = pOp->p1;
  i64 v = 0;
  VdbeCursor *pC;
  assert( i>=0 && i<p->nCursor );
  assert( p->apCsr[i]!=0 );
  if( (pC = p->apCsr[i])->pCursor==0 ){
    /* The zero initialization above is all that is needed */
  }else{
    /* The next rowid or record number (different terms for the same
    ** thing) is obtained in a two-step algorithm.

*/
case OP_Insert: {
  Mem *pData = &p->aMem[pOp->p2];
  Mem *pKey = &p->aMem[pOp->p3];

  i64 iKey;   /* The integer ROWID or key for the record to be inserted */
  int i = pOp->p1;
  VdbeCursor *pC;
  assert( i>=0 && i<p->nCursor );
  pC = p->apCsr[i];
  assert( pC!=0 );
  assert( pC->pCursor!=0 || pC->pseudoTable );
  assert( pKey->flags & MEM_Int );
  assert( pC->isTable );
  REGISTER_TRACE(pOp->p2, pData);

** pointing to.  The update hook will be invoked, if it exists.
** If P4 is not NULL then the P1 cursor must have been positioned
** using OP_NotFound prior to invoking this opcode.
*/
case OP_Delete: {
  int i = pOp->p1;
  i64 iKey;
  VdbeCursor *pC;

  assert( i>=0 && i<p->nCursor );
  pC = p->apCsr[i];
  assert( pC!=0 );
  assert( pC->pCursor!=0 );  /* Only valid for real tables, no pseudotables */

  /* If the update-hook will be invoked, set iKey to the rowid of the

**
** If the P1 cursor must be pointing to a valid row (not a NULL row)
** of a real table, not a pseudo-table.
*/
case OP_RowKey:
case OP_RowData: {
  int i = pOp->p1;
  VdbeCursor *pC;
  BtCursor *pCrsr;
  u32 n;

  pOut = &p->aMem[pOp->p2];

  /* Note that RowKey and RowData are really exactly the same instruction */
  assert( i>=0 && i<p->nCursor );

/* Opcode: Rowid P1 P2 * * *
**
** Store in register P2 an integer which is the key of the table entry that
** P1 is currently point to.
*/
case OP_Rowid: {                 /* out2-prerelease */
  int i = pOp->p1;
  VdbeCursor *pC;
  i64 v;

  assert( i>=0 && i<p->nCursor );
  pC = p->apCsr[i];
  assert( pC!=0 );
  rc = sqlite3VdbeCursorMoveto(pC);
  if( rc ) goto abort_due_to_error;

**
** Move the cursor P1 to a null row.  Any OP_Column operations
** that occur while the cursor is on the null row will always
** write a NULL.
*/
case OP_NullRow: {
  int i = pOp->p1;
  VdbeCursor *pC;

  assert( i>=0 && i<p->nCursor );
  pC = p->apCsr[i];
  assert( pC!=0 );
  pC->nullRow = 1;
  pC->rowidIsValid = 0;
  if( pC->pCursor ){

** will refer to the last entry in the database table or index.
** If the table or index is empty and P2>0, then jump immediately to P2.
** If P2 is 0 or if the table or index is not empty, fall through
** to the following instruction.
*/
case OP_Last: {        /* jump */
  int i = pOp->p1;
  VdbeCursor *pC;
  BtCursor *pCrsr;
  int res;

  assert( i>=0 && i<p->nCursor );
  pC = p->apCsr[i];
  assert( pC!=0 );
  pCrsr = pC->pCursor;

** will refer to the first entry in the database table or index.
** If the table or index is empty and P2>0, then jump immediately to P2.
** If P2 is 0 or if the table or index is not empty, fall through
** to the following instruction.
*/
case OP_Rewind: {        /* jump */
  int i = pOp->p1;
  VdbeCursor *pC;
  BtCursor *pCrsr;
  int res;

  assert( i>=0 && i<p->nCursor );
  pC = p->apCsr[i];
  assert( pC!=0 );
  if( (pCrsr = pC->pCursor)!=0 ){

** to the following instruction.  But if the cursor backup was successful,
** jump immediately to P2.
**
** The P1 cursor must be for a real table, not a pseudo-table.
*/
case OP_Prev:          /* jump */
case OP_Next: {        /* jump */
  VdbeCursor *pC;
  BtCursor *pCrsr;
  int res;

  CHECK_FOR_INTERRUPT;
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  if( pC==0 ){

** insert is likely to be an append.
**
** This instruction only works for indices.  The equivalent instruction
** for tables is OP_Insert.
*/
case OP_IdxInsert: {        /* in2 */
  int i = pOp->p1;
  VdbeCursor *pC;
  BtCursor *pCrsr;
  assert( i>=0 && i<p->nCursor );
  assert( p->apCsr[i]!=0 );
  assert( pIn2->flags & MEM_Blob );
  if( (pCrsr = (pC = p->apCsr[i])->pCursor)!=0 ){
    assert( pC->isTable==0 );
    rc = ExpandBlob(pIn2);

**
** The content of P3 registers starting at register P2 form
** an unpacked index key. This opcode removes that entry from the 
** index opened by cursor P1.
*/
case OP_IdxDelete: {
  int i = pOp->p1;
  VdbeCursor *pC;
  BtCursor *pCrsr;
  assert( pOp->p3>0 );
  assert( pOp->p2>0 && pOp->p2+pOp->p3<=p->nMem );
  assert( i>=0 && i<p->nCursor );
  assert( p->apCsr[i]!=0 );
  if( (pCrsr = (pC = p->apCsr[i])->pCursor)!=0 ){
    int res;

** the rowid of the table entry to which this index entry points.
**
** See also: Rowid, MakeIdxRec.
*/
case OP_IdxRowid: {              /* out2-prerelease */
  int i = pOp->p1;
  BtCursor *pCrsr;
  VdbeCursor *pC;

  assert( i>=0 && i<p->nCursor );
  assert( p->apCsr[i]!=0 );
  if( (pCrsr = (pC = p->apCsr[i])->pCursor)!=0 ){
    i64 rowid;

    assert( pC->deferredMoveto==0 );

**
** If P5 is non-zero then the key value is increased by an epsilon prior 
** to the comparison.  This makes the opcode work like IdxLE.
*/
case OP_IdxLT:          /* jump, in3 */
case OP_IdxGE: {        /* jump, in3 */
  int i= pOp->p1;
  VdbeCursor *pC;

  assert( i>=0 && i<p->nCursor );
  assert( p->apCsr[i]!=0 );
  if( (pC = p->apCsr[i])->pCursor!=0 ){
    int res;
    UnpackedRecord r;
    assert( pC->deferredMoveto==0 );

/* Opcode: VOpen P1 * * P4 *
**
** P4 is a pointer to a virtual table object, an sqlite3_vtab structure.
** P1 is a cursor number.  This opcode opens a cursor to the virtual
** table and stores that cursor in P1.
*/
case OP_VOpen: {
  VdbeCursor *pCur = 0;
  sqlite3_vtab_cursor *pVtabCursor = 0;

  sqlite3_vtab *pVtab = pOp->p4.pVtab;
  sqlite3_module *pModule = (sqlite3_module *)pVtab->pModule;

  assert(pVtab && pModule);
  if( sqlite3SafetyOff(db) ) goto abort_due_to_misuse;

  int iQuery;
  const sqlite3_module *pModule;
  Mem *pQuery = &p->aMem[pOp->p3];
  Mem *pArgc = &pQuery[1];
  sqlite3_vtab_cursor *pVtabCursor;
  sqlite3_vtab *pVtab;

  VdbeCursor *pCur = p->apCsr[pOp->p1];

  REGISTER_TRACE(pOp->p3, pQuery);
  assert( pCur->pVtabCursor );
  pVtabCursor = pCur->pVtabCursor;
  pVtab = pVtabCursor->pVtab;
  pModule = pVtab->pModule;

** Store into register P2  the rowid of
** the virtual-table that the P1 cursor is pointing to.
*/
case OP_VRowid: {             /* out2-prerelease */
  sqlite3_vtab *pVtab;
  const sqlite3_module *pModule;
  sqlite_int64 iRow;
  VdbeCursor *pCur = p->apCsr[pOp->p1];

  assert( pCur->pVtabCursor );
  if( pCur->nullRow ){
    break;
  }
  pVtab = pCur->pVtabCursor->pVtab;
  pModule = pVtab->pModule;

*/
case OP_VColumn: {
  sqlite3_vtab *pVtab;
  const sqlite3_module *pModule;
  Mem *pDest;
  sqlite3_context sContext;

  VdbeCursor *pCur = p->apCsr[pOp->p1];
  assert( pCur->pVtabCursor );
  assert( pOp->p3>0 && pOp->p3<=p->nMem );
  pDest = &p->aMem[pOp->p3];
  if( pCur->nullRow ){
    sqlite3VdbeMemSetNull(pDest);
    break;
  }

** the end of its result set, then fall through to the next instruction.
*/
case OP_VNext: {   /* jump */
  sqlite3_vtab *pVtab;
  const sqlite3_module *pModule;
  int res = 0;

  VdbeCursor *pCur = p->apCsr[pOp->p1];
  assert( pCur->pVtabCursor );
  if( pCur->nullRow ){
    break;
  }
  pVtab = pCur->pVtabCursor->pVtab;
  pModule = pVtab->pModule;
  assert( pModule->xNext );

*************************************************************************
** This is the header file for information that is private to the
** VDBE.  This information used to all be at the top of the single
** source code file "vdbe.c".  When that file became too big (over
** 6000 lines long) it was split up into several smaller files and
** this header information was factored out.
**
** $Id: vdbeInt.h,v 1.156 2008/11/03 20:55:07 drh Exp $
*/
#ifndef _VDBEINT_H_
#define _VDBEINT_H_

/*
** intToKey() and keyToInt() used to transform the rowid.  But with
** the latest versions of the design they are no-ops.

** loop over all entries of the Btree.  You can also insert new BTree
** entries or retrieve the key or data from the entry that the cursor
** is currently pointing to.
** 
** Every cursor that the virtual machine has open is represented by an
** instance of the following structure.
**
** If the VdbeCursor.isTriggerRow flag is set it means that this cursor is
** really a single row that represents the NEW or OLD pseudo-table of
** a row trigger.  The data for the row is stored in VdbeCursor.pData and
** the rowid is in VdbeCursor.iKey.
*/
struct VdbeCursor {
  BtCursor *pCursor;    /* The cursor structure of the backend */
  int iDb;              /* Index of cursor database in db->aDb[] (or -1) */
  i64 lastRowid;        /* Last rowid from a Next or NextIdx operation */
  i64 nextRowid;        /* Next rowid returned by OP_NewRowid */
  Bool zeroed;          /* True if zeroed out and ready for reuse */
  Bool rowidIsValid;    /* True if lastRowid is valid */
  Bool atFirst;         /* True if pointing to first entry */

  */
  int cacheStatus;      /* Cache is valid if this matches Vdbe.cacheCtr */
  int payloadSize;      /* Total number of bytes in the record */
  u32 *aType;           /* Type values for all entries in the record */
  u32 *aOffset;         /* Cached offsets to the start of each columns data */
  u8 *aRow;             /* Data for the current row, if all on one page */
};
typedef struct VdbeCursor VdbeCursor;

/*
** A value for VdbeCursor.cacheValid that means the cache is always invalid.
*/
#define CACHE_STALE 0

/*
** Internally, the vdbe manipulates nearly all SQL values as Mem
** structures. Each Mem struct may cache multiple representations (string,
** integer etc.) of the same value.  A value (and therefore Mem structure)

  Op *aOp;            /* Space to hold the virtual machine's program */
  int nLabel;         /* Number of labels used */
  int nLabelAlloc;    /* Number of slots allocated in aLabel[] */
  int *aLabel;        /* Space to hold the labels */
  Mem **apArg;        /* Arguments to currently executing user function */
  Mem *aColName;      /* Column names to return */
  int nCursor;        /* Number of slots in apCsr[] */
  VdbeCursor **apCsr; /* One element of this array for each open cursor */
  int nVar;           /* Number of entries in aVar[] */
  Mem *aVar;          /* Values for the OP_Variable opcode. */
  char **azVar;       /* Name of variables */
  int okVar;          /* True if azVar[] has been initialized */
  int magic;              /* Magic number for sanity checking */
  int nMem;               /* Number of memory locations currently allocated */
  Mem *aMem;              /* The memory locations */
  int nCallback;          /* Number of callbacks invoked so far */
  int cacheCtr;           /* VdbeCursor row cache generation counter */
  Fifo sFifo;             /* A list of ROWIDs */
  int contextStackTop;    /* Index of top element in the context stack */
  int contextStackDepth;  /* The size of the "context" stack */
  Context *contextStack;  /* Stack used by opcodes ContextPush & ContextPop*/
  int pc;                 /* The program counter */
  int rc;                 /* Value to return */
  unsigned uniqueCnt;     /* Used by OP_MakeRecord when P2!=0 */

#define VDBE_MAGIC_RUN      0xbdf20da3    /* VDBE is ready to execute */
#define VDBE_MAGIC_HALT     0x519c2973    /* VDBE has completed execution */
#define VDBE_MAGIC_DEAD     0xb606c3c8    /* The VDBE has been deallocated */

/*
** Function prototypes
*/
void sqlite3VdbeFreeCursor(Vdbe *, VdbeCursor*);
void sqliteVdbePopStack(Vdbe*,int);
int sqlite3VdbeCursorMoveto(VdbeCursor*);
#if defined(SQLITE_DEBUG) || defined(VDBE_PROFILE)
void sqlite3VdbePrintOp(FILE*, int, Op*);
#endif
int sqlite3VdbeSerialTypeLen(u32);
u32 sqlite3VdbeSerialType(Mem*, int);
int sqlite3VdbeSerialPut(unsigned char*, int, Mem*, int);
int sqlite3VdbeSerialGet(const unsigned char*, u32, Mem*);
void sqlite3VdbeDeleteAuxData(VdbeFunc*, int);

int sqlite2BtreeKeyCompare(BtCursor *, const void *, int, int, int *);
int sqlite3VdbeIdxKeyCompare(VdbeCursor*,UnpackedRecord*,int*);
int sqlite3VdbeIdxRowid(BtCursor *, i64 *);
int sqlite3MemCompare(const Mem*, const Mem*, const CollSeq*);
int sqlite3VdbeExec(Vdbe*);
int sqlite3VdbeList(Vdbe*);
int sqlite3VdbeHalt(Vdbe*);
int sqlite3VdbeChangeEncoding(Mem *, int);
int sqlite3VdbeMemTooBig(Mem*);

**
*************************************************************************
** This file contains code used for creating, destroying, and populating
** a VDBE (or an "sqlite3_stmt" as it is known to the outside world.)  Prior
** to version 2.8.7, all this code was combined into the vdbe.c source file.
** But that file was getting too big so this subroutines were split out.
**
** $Id: vdbeaux.c,v 1.415 2008/11/03 20:55:07 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
#include "vdbeInt.h"

   * state.
   */
  p->magic = VDBE_MAGIC_RUN;

  /* For each cursor required, also allocate a memory cell. Memory
  ** cells (nMem+1-nCursor)..nMem, inclusive, will never be used by
  ** the vdbe program. Instead they are used to allocate space for
  ** VdbeCursor/BtCursor structures. The blob of memory associated with 
  ** cursor 0 is stored in memory cell nMem. Memory cell (nMem-1)
  ** stores the blob of memory associated with cursor 1, etc.
  **
  ** See also: allocateCursor().
  */
  nMem += nCursor;

      p->nMem = nMem = 10;
    }
    p->aMem = sqlite3DbMallocZero(db,
        nMem*sizeof(Mem)               /* aMem */
      + nVar*sizeof(Mem)               /* aVar */
      + nArg*sizeof(Mem*)              /* apArg */
      + nVar*sizeof(char*)             /* azVar */
      + nCursor*sizeof(VdbeCursor*)+1  /* apCsr */
    );
    if( !db->mallocFailed ){
      p->aMem--;             /* aMem[] goes from 1..nMem */
      p->nMem = nMem;        /*       not from 0..nMem-1 */
      p->aVar = &p->aMem[nMem+1];
      p->nVar = nVar;
      p->okVar = 0;
      p->apArg = (Mem**)&p->aVar[nVar];
      p->azVar = (char**)&p->apArg[nArg];
      p->apCsr = (VdbeCursor**)&p->azVar[nVar];
      p->nCursor = nCursor;
      for(n=0; n<nVar; n++){
        p->aVar[n].flags = MEM_Null;
        p->aVar[n].db = db;
      }
      for(n=1; n<=nMem; n++){
        p->aMem[n].flags = MEM_Null;

#endif
}

/*
** Close a VDBE cursor and release all the resources that cursor 
** happens to hold.
*/
void sqlite3VdbeFreeCursor(Vdbe *p, VdbeCursor *pCx){
  if( pCx==0 ){
    return;
  }
  if( pCx->pBt ){
    sqlite3BtreeClose(pCx->pBt);
    /* The pCx->pCursor will be close automatically, if it exists, by
    ** the call above. */

** Close all cursors except for VTab cursors that are currently
** in use.
*/
static void closeAllCursorsExceptActiveVtabs(Vdbe *p){
  int i;
  if( p->apCsr==0 ) return;
  for(i=0; i<p->nCursor; i++){
    VdbeCursor *pC = p->apCsr[i];
    if( pC && (!p->inVtabMethod || !pC->pVtabCursor) ){
      sqlite3VdbeFreeCursor(p, pC);
      p->apCsr[i] = 0;
    }
  }
}

}

/*
** If a MoveTo operation is pending on the given cursor, then do that
** MoveTo now.  Return an error code.  If no MoveTo is pending, this
** routine does nothing and returns SQLITE_OK.
*/
int sqlite3VdbeCursorMoveto(VdbeCursor *p){
  if( p->deferredMoveto ){
    int res, rc;
#ifdef SQLITE_TEST
    extern int sqlite3_search_count;
#endif
    assert( p->isTable );
    rc = sqlite3BtreeMovetoUnpacked(p->pCursor, 0, p->movetoTarget, 0, &res);

** is ignored as well.  Hence, this routine only compares the prefixes 
** of the keys prior to the final rowid, not the entire key.
**
** pUnpacked may be an unpacked version of pKey,nKey.  If pUnpacked is
** supplied it is used in place of pKey,nKey.
*/
int sqlite3VdbeIdxKeyCompare(
  VdbeCursor *pC,             /* The cursor to compare against */
  UnpackedRecord *pUnpacked,  /* Unpacked version of pKey and nKey */
  int *res                    /* Write the comparison result here */
){
  i64 nCellKey = 0;
  int rc;
  BtCursor *pCur = pC->pCursor;
  Mem m;