SQLite

**    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 UPDATE statements.
**
** $Id: update.c,v 1.70.2.1 2004/04/29 16:16:29 drh Exp $
*/
#include "sqliteInt.h"

/*
** Process an UPDATE statement.
**
**   UPDATE OR IGNORE table_wxyz SET a=b, c=d WHERE e<5 AND f NOT NULL;
**          \_______/ \________/     \______/       \________________/
*            onError   pTabList      pChanges             pWhere
*/
void sqliteUpdate(
  Parse *pParse,         /* The parser context */
  SrcList *pTabList,     /* The table in which we should change things */
  ExprList *pChanges,    /* Things to be changed */
  Expr *pWhere,          /* The WHERE clause.  May be null */
  int onError            /* How to handle constraint errors */
){
  int i, j;              /* Loop counters */
  Table *pTab;           /* The table to be updated */
  int loopStart;         /* VDBE instruction address of the start of the loop */
  int jumpInst;          /* Addr of VDBE instruction to jump out of loop */
  WhereInfo *pWInfo;     /* Information about the WHERE clause */
  Vdbe *v;               /* The virtual database engine */
  Index *pIdx;           /* For looping over indices */
  int nIdx;              /* Number of indices that need updating */
  int nIdxTotal;         /* Total number of indices */
  int iCur;              /* VDBE Cursor number of pTab */
  sqlite *db;            /* The database structure */
  Index **apIdx = 0;     /* An array of indices that need updating too */
  char *aIdxUsed = 0;    /* aIdxUsed[i]==1 if the i-th index is used */
  int *aXRef = 0;        /* aXRef[i] is the index in pChanges->a[] of the
                         ** an expression for the i-th column of the table.
                         ** aXRef[i]==-1 if the i-th column is not changed. */
  int chngRecno;         /* True if the record number is being changed */
  Expr *pRecnoExpr;      /* Expression defining the new record number */
  int openAll;           /* True if all indices need to be opened */
  int isView;            /* Trying to update a view */
  int iStackDepth;       /* Index of memory cell holding stack depth */
  AuthContext sContext;  /* The authorization context */

  int before_triggers;         /* True if there are any BEFORE triggers */
  int after_triggers;          /* True if there are any AFTER triggers */
  int row_triggers_exist = 0;  /* True if any row triggers exist */

  int newIdx      = -1;  /* index of trigger "new" temp table       */
  int oldIdx      = -1;  /* index of trigger "old" temp table       */

  sContext.pParse = 0;
  if( pParse->nErr || sqlite_malloc_failed ) goto update_cleanup;
  db = pParse->db;
  assert( pTabList->nSrc==1 );
  iStackDepth = pParse->nMem++;

  /* Locate the table which we want to update. 
  */
  pTab = sqliteSrcListLookup(pParse, pTabList);
  if( pTab==0 ) goto update_cleanup;
  before_triggers = sqliteTriggersExist(pParse, pTab->pTrigger, 
            TK_UPDATE, TK_BEFORE, TK_ROW, pChanges);

    */
    sqliteVdbeAddOp(v, OP_OpenPseudo, oldIdx, 0);
    sqliteVdbeAddOp(v, OP_OpenPseudo, newIdx, 0);

    /* The top of the update loop for when there are triggers.
    */
    sqliteVdbeAddOp(v, OP_ListRewind, 0, 0);
    sqliteVdbeAddOp(v, OP_StackDepth, 0, 0);
    sqliteVdbeAddOp(v, OP_MemStore, iStackDepth, 1);
    loopStart = sqliteVdbeAddOp(v, OP_MemLoad, iStackDepth, 0);
    sqliteVdbeAddOp(v, OP_StackReset, 0, 0);
    jumpInst = sqliteVdbeAddOp(v, OP_ListRead, 0, 0);
    sqliteVdbeAddOp(v, OP_Dup, 0, 0);

    /* Open a cursor and make it point to the record that is
    ** being updated.
    */
    sqliteVdbeAddOp(v, OP_Dup, 0, 0);
    if( !isView ){

    if( !isView ){
      sqliteVdbeAddOp(v, OP_Close, iCur, 0);
    }

    /* Fire the BEFORE and INSTEAD OF triggers
    */
    if( sqliteCodeRowTrigger(pParse, TK_UPDATE, pChanges, TK_BEFORE, pTab, 
          newIdx, oldIdx, onError, loopStart) ){
      goto update_cleanup;
    }
  }

  if( !isView ){
    /* 
    ** Open every index that needs updating.  Note that if any

    ** the old data for each record to be updated because some columns
    ** might not change and we will need to copy the old value.
    ** Also, the old data is needed to delete the old index entires.
    ** So make the cursor point at the old record.
    */
    if( !row_triggers_exist ){
      sqliteVdbeAddOp(v, OP_ListRewind, 0, 0);
      jumpInst = loopStart = sqliteVdbeAddOp(v, OP_ListRead, 0, 0);
      sqliteVdbeAddOp(v, OP_Dup, 0, 0);
    }
    sqliteVdbeAddOp(v, OP_NotExists, iCur, loopStart);

    /* If the record number will change, push the record number as it
    ** will be after the update. (The old record number is currently
    ** on top of the stack.)
    */
    if( chngRecno ){
      sqliteExprCode(pParse, pRecnoExpr);

        sqliteExprCode(pParse, pChanges->a[j].pExpr);
      }
    }

    /* Do constraint checks
    */
    sqliteGenerateConstraintChecks(pParse, pTab, iCur, aIdxUsed, chngRecno, 1,
                                   onError, loopStart);

    /* Delete the old indices for the current record.
    */
    sqliteGenerateRowIndexDelete(db, v, pTab, iCur, aIdxUsed);

    /* If changing the record number, delete the old record.
    */

        if( openAll || aIdxUsed[i] )
          sqliteVdbeAddOp(v, OP_Close, iCur+i+1, 0);
      }
      sqliteVdbeAddOp(v, OP_Close, iCur, 0);
      pParse->nTab = iCur;
    }
    if( sqliteCodeRowTrigger(pParse, TK_UPDATE, pChanges, TK_AFTER, pTab, 
          newIdx, oldIdx, onError, loopStart) ){
      goto update_cleanup;
    }
  }

  /* Repeat the above with the next record to be updated, until
  ** all record selected by the WHERE clause have been updated.
  */
  sqliteVdbeAddOp(v, OP_Goto, 0, loopStart);
  sqliteVdbeChangeP2(v, jumpInst, sqliteVdbeCurrentAddr(v));
  sqliteVdbeAddOp(v, OP_ListReset, 0, 0);

  /* Close all tables if there were no FOR EACH ROW triggers */
  if( !row_triggers_exist ){
    for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
      if( openAll || aIdxUsed[i] ){
        sqliteVdbeAddOp(v, OP_Close, iCur+i+1, 0);

**
** 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 1.268.2.1 2004/04/29 16:16:30 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*

*/
case OP_Vacuum: {
  if( sqliteSafetyOff(db) ) goto abort_due_to_misuse; 
  rc = sqliteRunVacuum(&p->zErrMsg, db);
  if( sqliteSafetyOn(db) ) goto abort_due_to_misuse;
  break;
}

/* Opcode: StackDepth * * *
**
** Push an integer onto the stack which is the depth of the stack prior
** to that integer being pushed.
*/
case OP_StackDepth: {
  int depth = (&pTos[1]) - p->aStack;
  pTos++;
  pTos->i = depth;
  pTos->flags = MEM_Int;
  break;
}

/* Opcode: StackReset * * *
**
** Pop a single integer off of the stack.  Then pop the stack
** as many times as necessary to get the depth of the stack down
** to the value of the integer that was popped.
*/
case OP_StackReset: {
  int depth, goal;
  assert( pTos>=p->aStack );
  Integerify(pTos);
  goal = pTos->i;
  depth = (&pTos[1]) - p->aStack;
  assert( goal<depth );
  popStack(&pTos, depth-goal);
  break;
}

/* An other opcode is illegal...
*/
default: {
  sqlite_snprintf(sizeof(zBuf),zBuf,"%d",pOp->opcode);
  sqliteSetString(&p->zErrMsg, "unknown opcode ", zBuf, (char*)0);
  rc = SQLITE_INTERNAL;