vdbe.c

sqlite数据库管理系统开放源码

/*
** 2001 September 15
**
** 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.
**
*************************************************************************
** The code in this file implements execution method of the 
** Virtual Database Engine (VDBE).  A separate file ("vdbeaux.c")
** handles housekeeping details such as creating and deleting
** VDBE instances.  This file is solely interested in executing
** the VDBE program.
**
** In the external interface, an "sqlite_vm*" is an opaque pointer
** to a VDBE.
**
** The SQL parser generates a program which is then executed by
** the VDBE to do the work of the SQL statement.  VDBE programs are 
** similar in form to assembly language.  The program consists of
** a linear sequence of operations.  Each operation has an opcode 
** and 3 operands.  Operands P1 and P2 are integers.  Operand P3 
** is a null-terminated string.   The P2 operand must be non-negative.
** Opcodes will typically ignore one or more operands.  Many opcodes
** ignore all three operands.
**
** Computation results are stored on a stack.  Each entry on the
** stack is either an integer, a null-terminated string, a floating point
** number, or the SQL "NULL" value.  An inplicit conversion from one
** type to the other occurs as necessary.
** 
** Most of the code in this file is taken up by the sqliteVdbeExec()
** function which does the work of interpreting a VDBE program.
** But other routines are also provided to help in building up
** a program instruction by instruction.
**
** 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 1.268.2.4 2004/10/01 15:11:13 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*
** The following global variable is incremented every time a cursor
** moves, either by the OP_MoveTo or the OP_Next opcode.  The test
** procedures use this information to make sure that indices are
** working correctly.  This variable has no function other than to
** help verify the correct operation of the library.
*/
int sqlite_search_count = 0;

/*
** When this global variable is positive, it gets decremented once before
** each instruction in the VDBE.  When reaches zero, the SQLITE_Interrupt
** of the db.flags field is set in order to simulate an interrupt.
**
** This facility is used for testing purposes only.  It does not function
** in an ordinary build.
*/
int sqlite_interrupt_count = 0;

/*
** Advance the virtual machine to the next output row.
**
** The return vale will be either SQLITE_BUSY, SQLITE_DONE, 
** SQLITE_ROW, SQLITE_ERROR, or SQLITE_MISUSE.
**
** SQLITE_BUSY means that the virtual machine attempted to open
** a locked database and there is no busy callback registered.
** Call sqlite_step() again to retry the open.  *pN is set to 0
** and *pazColName and *pazValue are both set to NULL.
**
** SQLITE_DONE means that the virtual machine has finished
** executing.  sqlite_step() should not be called again on this
** virtual machine.  *pN and *pazColName are set appropriately
** but *pazValue is set to NULL.
**
** SQLITE_ROW means that the virtual machine has generated another
** row of the result set.  *pN is set to the number of columns in
** the row.  *pazColName is set to the names of the columns followed
** by the column datatypes.  *pazValue is set to the values of each
** column in the row.  The value of the i-th column is (*pazValue)[i].
** The name of the i-th column is (*pazColName)[i] and the datatype
** of the i-th column is (*pazColName)[i+*pN].
**
** SQLITE_ERROR means that a run-time error (such as a constraint
** violation) has occurred.  The details of the error will be returned
** by the next call to sqlite_finalize().  sqlite_step() should not
** be called again on the VM.
**
** SQLITE_MISUSE means that the this routine was called inappropriately.
** Perhaps it was called on a virtual machine that had already been
** finalized or on one that had previously returned SQLITE_ERROR or
** SQLITE_DONE.  Or it could be the case the the same database connection
** is being used simulataneously by two or more threads.
*/
int sqlite_step(
  sqlite_vm *pVm,              /* The virtual machine to execute */
  int *pN,                     /* OUT: Number of columns in result */
  const char ***pazValue,      /* OUT: Column data */
  const char ***pazColName     /* OUT: Column names and datatypes */
){
  Vdbe *p = (Vdbe*)pVm;
  sqlite *db;
  int rc;

  if( p->magic!=VDBE_MAGIC_RUN ){
    return SQLITE_MISUSE;
  }
  db = p->db;
  if( sqliteSafetyOn(db) ){
    p->rc = SQLITE_MISUSE;
    return SQLITE_MISUSE;
  }
  if( p->explain ){
    rc = sqliteVdbeList(p);
  }else{
    rc = sqliteVdbeExec(p);
  }
  if( rc==SQLITE_DONE || rc==SQLITE_ROW ){
    if( pazColName ) *pazColName = (const char**)p->azColName;
    if( pN ) *pN = p->nResColumn;
  }else{
    if( pazColName) *pazColName = 0;
    if( pN ) *pN = 0;
  }
  if( pazValue ){
    if( rc==SQLITE_ROW ){
      *pazValue = (const char**)p->azResColumn;
    }else{
      *pazValue = 0;
    }
  }
  if( sqliteSafetyOff(db) ){
    return SQLITE_MISUSE;
  }
  return rc;
}

/*
** Insert a new aggregate element and make it the element that
** has focus.
**
** Return 0 on success and 1 if memory is exhausted.
*/
static int AggInsert(Agg *p, char *zKey, int nKey){
  AggElem *pElem, *pOld;
  int i;
  Mem *pMem;
  pElem = sqliteMalloc( sizeof(AggElem) + nKey +
                        (p->nMem-1)*sizeof(pElem->aMem[0]) );
  if( pElem==0 ) return 1;
  pElem->zKey = (char*)&pElem->aMem[p->nMem];
  memcpy(pElem->zKey, zKey, nKey);
  pElem->nKey = nKey;
  pOld = sqliteHashInsert(&p->hash, pElem->zKey, pElem->nKey, pElem);
  if( pOld!=0 ){
    assert( pOld==pElem );  /* Malloc failed on insert */
    sqliteFree(pOld);
    return 0;
  }
  for(i=0, pMem=pElem->aMem; i<p->nMem; i++, pMem++){
    pMem->flags = MEM_Null;
  }
  p->pCurrent = pElem;
  return 0;
}

/*
** Get the AggElem currently in focus
*/
#define AggInFocus(P)   ((P).pCurrent ? (P).pCurrent : _AggInFocus(&(P)))
static AggElem *_AggInFocus(Agg *p){
  HashElem *pElem = sqliteHashFirst(&p->hash);
  if( pElem==0 ){
    AggInsert(p,"",1);
    pElem = sqliteHashFirst(&p->hash);
  }
  return pElem ? sqliteHashData(pElem) : 0;
}

/*
** Convert the given stack entity into a string if it isn't one
** already.
*/
#define Stringify(P) if(((P)->flags & MEM_Str)==0){hardStringify(P);}
static int hardStringify(Mem *pStack){
  int fg = pStack->flags;
  if( fg & MEM_Real ){
    sqlite_snprintf(sizeof(pStack->zShort),pStack->zShort,"%.15g",pStack->r);
  }else if( fg & MEM_Int ){
    sqlite_snprintf(sizeof(pStack->zShort),pStack->zShort,"%d",pStack->i);
  }else{
    pStack->zShort[0] = 0;
  }
  pStack->z = pStack->zShort;
  pStack->n = strlen(pStack->zShort)+1;
  pStack->flags = MEM_Str | MEM_Short;
  return 0;
}

/*
** Convert the given stack entity into a string that has been obtained
** from sqliteMalloc().  This is different from Stringify() above in that
** Stringify() will use the NBFS bytes of static string space if the string
** will fit but this routine always mallocs for space.
** Return non-zero if we run out of memory.
*/
#define Dynamicify(P) (((P)->flags & MEM_Dyn)==0 ? hardDynamicify(P):0)
static int hardDynamicify(Mem *pStack){
  int fg = pStack->flags;
  char *z;
  if( (fg & MEM_Str)==0 ){
    hardStringify(pStack);
  }
  assert( (fg & MEM_Dyn)==0 );
  z = sqliteMallocRaw( pStack->n );
  if( z==0 ) return 1;
  memcpy(z, pStack->z, pStack->n);
  pStack->z = z;
  pStack->flags |= MEM_Dyn;
  return 0;
}

/*
** An ephemeral string value (signified by the MEM_Ephem flag) contains
** a pointer to a dynamically allocated string where some other entity
** is responsible for deallocating that string.  Because the stack entry
** does not control the string, it might be deleted without the stack
** entry knowing it.
**
** This routine converts an ephemeral string into a dynamically allocated
** string that the stack entry itself controls.  In other words, it
** converts an MEM_Ephem string into an MEM_Dyn string.
*/
#define Deephemeralize(P) \
   if( ((P)->flags&MEM_Ephem)!=0 && hardDeephem(P) ){ goto no_mem;}
static int hardDeephem(Mem *pStack){
  char *z;
  assert( (pStack->flags & MEM_Ephem)!=0 );
  z = sqliteMallocRaw( pStack->n );
  if( z==0 ) return 1;
  memcpy(z, pStack->z, pStack->n);
  pStack->z = z;
  pStack->flags &= ~MEM_Ephem;
  pStack->flags |= MEM_Dyn;
  return 0;
}

/*
** Release the memory associated with the given stack level.  This
** leaves the Mem.flags field in an inconsistent state.
*/
#define Release(P) if((P)->flags&MEM_Dyn){ sqliteFree((P)->z); }

/*
** Pop the stack N times.
*/
static void popStack(Mem **ppTos, int N){
  Mem *pTos = *ppTos;
  while( N>0 ){
    N--;
    Release(pTos);
    pTos--;
  }
  *ppTos = pTos;
}

/*
** Return TRUE if zNum is a 32-bit signed integer and write
** the value of the integer into *pNum.  If zNum is not an integer
** or is an integer that is too large to be expressed with just 32
** bits, then return false.
**
** Under Linux (RedHat 7.2) this routine is much faster than atoi()
** for converting strings into integers.
*/
static int toInt(const char *zNum, int *pNum){
  int v = 0;
  int neg;
  int i, c;
  if( *zNum=='-' ){
    neg = 1;
    zNum++;
  }else if( *zNum=='+' ){
    neg = 0;
    zNum++;
  }else{
    neg = 0;
  }
  for(i=0; (c=zNum[i])>='0' && c<='9'; i++){
    v = v*10 + c - '0';
  }
  *pNum = neg ? -v : v;
  return c==0 && i>0 && (i<10 || (i==10 && memcmp(zNum,"2147483647",10)<=0));
}

/*
** Convert the given stack entity into a integer if it isn't one
** already.
**
** Any prior string or real representation is invalidated.  
** NULLs are converted into 0.
*/
#define Integerify(P) if(((P)->flags&MEM_Int)==0){ hardIntegerify(P); }
static void hardIntegerify(Mem *pStack){
  if( pStack->flags & MEM_Real ){
    pStack->i = (int)pStack->r;
    Release(pStack);
  }else if( pStack->flags & MEM_Str ){
    toInt(pStack->z, &pStack->i);
    Release(pStack);
  }else{
    pStack->i = 0;
  }
  pStack->flags = MEM_Int;
}

/*
** Get a valid Real representation for the given stack element.
**
** Any prior string or integer representation is retained.
** NULLs are converted into 0.0.
*/
#define Realify(P) if(((P)->flags&MEM_Real)==0){ hardRealify(P); }
static void hardRealify(Mem *pStack){
  if( pStack->flags & MEM_Str ){
    pStack->r = sqliteAtoF(pStack->z, 0);
  }else if( pStack->flags & MEM_Int ){
    pStack->r = pStack->i;
  }else{
    pStack->r = 0.0;
  }
  pStack->flags |= MEM_Real;
}

/*
** The parameters are pointers to the head of two sorted lists
** of Sorter structures.  Merge these two lists together and return
** a single sorted list.  This routine forms the core of the merge-sort
** algorithm.
**
** In the case of a tie, left sorts in front of right.
*/
static Sorter *Merge(Sorter *pLeft, Sorter *pRight){
  Sorter sHead;
  Sorter *pTail;
  pTail = &sHead;
  pTail->pNext = 0;
  while( pLeft && pRight ){
    int c = sqliteSortCompare(pLeft->zKey, pRight->zKey);
    if( c<=0 ){
      pTail->pNext = pLeft;
      pLeft = pLeft->pNext;
    }else{
      pTail->pNext = pRight;
      pRight = pRight->pNext;
    }
    pTail = pTail->pNext;
  }
  if( pLeft ){
    pTail->pNext = pLeft;
  }else if( pRight ){
    pTail->pNext = pRight;
  }
  return sHead.pNext;
}

/*
** The following routine works like a replacement for the standard
** library routine fgets().  The difference is in how end-of-line (EOL)
** is handled.  Standard fgets() uses LF for EOL under unix, CRLF
** under windows, and CR under mac.  This routine accepts any of these
** character sequences as an EOL mark.  The EOL mark is replaced by
** a single LF character in zBuf.
*/
static char *vdbe_fgets(char *zBuf, int nBuf, FILE *in){
  int i, c;
  for(i=0; i<nBuf-1 && (c=getc(in))!=EOF; i++){
    zBuf[i] = c;
    if( c=='\r' || c=='\n' ){
      if( c=='\r' ){
        zBuf[i] = '\n';
        c = getc(in);
        if( c!=EOF && c!='\n' ) ungetc(c, in);
      }
      i++;
      break;
    }
  }
  zBuf[i]  = 0;
  return i>0 ? zBuf : 0;
}

/*
** Make sure there is space in the Vdbe structure to hold at least
** mxCursor cursors.  If there is not currently enough space, then
** allocate more.
**
** If a memory allocation error occurs, return 1.  Return 0 if
** everything works.
*/
static int expandCursorArraySize(Vdbe *p, int mxCursor){
  if( mxCursor>=p->nCursor ){
    Cursor *aCsr = sqliteRealloc( p->aCsr, (mxCursor+1)*sizeof(Cursor) );
    if( aCsr==0 ) return 1;
    p->aCsr = aCsr;
    memset(&p->aCsr[p->nCursor], 0, sizeof(Cursor)*(mxCursor+1-p->nCursor));
    p->nCursor = mxCursor+1;
  }
  return 0;
}

#ifdef VDBE_PROFILE
/*
** The following routine only works on pentium-class processors.
** It uses the RDTSC opcode to read cycle count value out of the
** processor and returns that value.  This can be used for high-res
** profiling.
*/