/*** 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.***************************************************************************** This file contains C code routines that are called by the parser** to handle UPDATE statements.**** $Id: update.c,v 1.133 2006/06/27 13:20:21 drh Exp $*/#include "sqliteInt.h"#ifndef SQLITE_OMIT_VIRTUALTABLE/* Forward declaration */static void updateVirtualTable(  Parse *pParse,       /* The parsing context */  SrcList *pSrc,       /* The virtual table to be modified */  Table *pTab,         /* The virtual table */  ExprList *pChanges,  /* The columns to change in the UPDATE statement */  Expr *pRowidExpr,    /* Expression used to recompute the rowid */  int *aXRef,          /* Mapping from columns of pTab to entries in pChanges */  Expr *pWhere         /* WHERE clause of the UPDATE statement */);#endif /* SQLITE_OMIT_VIRTUALTABLE *//*** The most recently coded instruction was an OP_Column to retrieve the** i-th column of table pTab. This routine sets the P3 parameter of the ** OP_Column to the default value, if any.**** The default value of a column is specified by a DEFAULT clause in the ** column definition. This was either supplied by the user when the table** was created, or added later to the table definition by an ALTER TABLE** command. If the latter, then the row-records in the table btree on disk** may not contain a value for the column and the default value, taken** from the P3 parameter of the OP_Column instruction, is returned instead.** If the former, then all row-records are guaranteed to include a value** for the column and the P3 value is not required.**** Column definitions created by an ALTER TABLE command may only have ** literal default values specified: a number, null or a string. (If a more** complicated default expression value was provided, it is evaluated ** when the ALTER TABLE is executed and one of the literal values written** into the sqlite_master table.)**** Therefore, the P3 parameter is only required if the default value for** the column is a literal number, string or null. The sqlite3ValueFromExpr()** function is capable of transforming these types of expressions into** sqlite3_value objects.*/void sqlite3ColumnDefault(Vdbe *v, Table *pTab, int i){  if( pTab && !pTab->pSelect ){    sqlite3_value *pValue;    u8 enc = ENC(sqlite3VdbeDb(v));    Column *pCol = &pTab->aCol[i];    sqlite3ValueFromExpr(pCol->pDflt, enc, pCol->affinity, &pValue);    if( pValue ){      sqlite3VdbeChangeP3(v, -1, (const char *)pValue, P3_MEM);    }else{      VdbeComment((v, "# %s.%s", pTab->zName, pCol->zName));    }  }}/*** 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 sqlite3Update(  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 addr = 0;          /* VDBE instruction address of the start of the 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 */  sqlite3 *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 chngRowid;         /* True if the record number is being changed */  Expr *pRowidExpr = 0;  /* Expression defining the new record number */  int openAll = 0;       /* True if all indices need to be opened */  AuthContext sContext;  /* The authorization context */  NameContext sNC;       /* The name-context to resolve expressions in */  int iDb;               /* Database containing the table being updated */#ifndef SQLITE_OMIT_TRIGGER  int isView;                  /* Trying to update a view */  int triggers_exist = 0;      /* True if any row triggers exist */#endif  int newIdx      = -1;  /* index of trigger "new" temp table       */  int oldIdx      = -1;  /* index of trigger "old" temp table       */  sContext.pParse = 0;  if( pParse->nErr || sqlite3MallocFailed() ){    goto update_cleanup;  }  db = pParse->db;  assert( pTabList->nSrc==1 );  /* Locate the table which we want to update.   */  pTab = sqlite3SrcListLookup(pParse, pTabList);  if( pTab==0 ) goto update_cleanup;  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);  /* Figure out if we have any triggers and if the table being  ** updated is a view  */#ifndef SQLITE_OMIT_TRIGGER  triggers_exist = sqlite3TriggersExist(pParse, pTab, TK_UPDATE, pChanges);  isView = pTab->pSelect!=0;#else# define triggers_exist 0# define isView 0#endif#ifdef SQLITE_OMIT_VIEW# undef isView# define isView 0#endif  if( sqlite3IsReadOnly(pParse, pTab, triggers_exist) ){    goto update_cleanup;  }  if( sqlite3ViewGetColumnNames(pParse, pTab) ){    goto update_cleanup;  }  aXRef = sqliteMallocRaw( sizeof(int) * pTab->nCol );  if( aXRef==0 ) goto update_cleanup;  for(i=0; i<pTab->nCol; i++) aXRef[i] = -1;  /* If there are FOR EACH ROW triggers, allocate cursors for the  ** special OLD and NEW tables  */  if( triggers_exist ){    newIdx = pParse->nTab++;    oldIdx = pParse->nTab++;  }  /* Allocate a cursors for the main database table and for all indices.  ** The index cursors might not be used, but if they are used they  ** need to occur right after the database cursor.  So go ahead and  ** allocate enough space, just in case.  */  pTabList->a[0].iCursor = iCur = pParse->nTab++;  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){    pParse->nTab++;  }  /* Initialize the name-context */  memset(&sNC, 0, sizeof(sNC));  sNC.pParse = pParse;  sNC.pSrcList = pTabList;  /* Resolve the column names in all the expressions of the  ** of the UPDATE statement.  Also find the column index  ** for each column to be updated in the pChanges array.  For each  ** column to be updated, make sure we have authorization to change  ** that column.  */  chngRowid = 0;  for(i=0; i<pChanges->nExpr; i++){    if( sqlite3ExprResolveNames(&sNC, pChanges->a[i].pExpr) ){      goto update_cleanup;    }    for(j=0; j<pTab->nCol; j++){      if( sqlite3StrICmp(pTab->aCol[j].zName, pChanges->a[i].zName)==0 ){        if( j==pTab->iPKey ){          chngRowid = 1;          pRowidExpr = pChanges->a[i].pExpr;        }        aXRef[j] = i;        break;      }    }    if( j>=pTab->nCol ){      if( sqlite3IsRowid(pChanges->a[i].zName) ){        chngRowid = 1;        pRowidExpr = pChanges->a[i].pExpr;      }else{        sqlite3ErrorMsg(pParse, "no such column: %s", pChanges->a[i].zName);        goto update_cleanup;      }    }#ifndef SQLITE_OMIT_AUTHORIZATION    {      int rc;      rc = sqlite3AuthCheck(pParse, SQLITE_UPDATE, pTab->zName,                           pTab->aCol[j].zName, db->aDb[iDb].zName);      if( rc==SQLITE_DENY ){        goto update_cleanup;      }else if( rc==SQLITE_IGNORE ){        aXRef[j] = -1;      }    }#endif  }  /* Allocate memory for the array apIdx[] and fill it with pointers to every  ** index that needs to be updated.  Indices only need updating if their  ** key includes one of the columns named in pChanges or if the record  ** number of the original table entry is changing.  */  for(nIdx=nIdxTotal=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdxTotal++){    if( chngRowid ){      i = 0;    }else {      for(i=0; i<pIdx->nColumn; i++){        if( aXRef[pIdx->aiColumn[i]]>=0 ) break;      }    }    if( i<pIdx->nColumn ) nIdx++;  }  if( nIdxTotal>0 ){    apIdx = sqliteMallocRaw( sizeof(Index*) * nIdx + nIdxTotal );    if( apIdx==0 ) goto update_cleanup;    aIdxUsed = (char*)&apIdx[nIdx];  }  for(nIdx=j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){    if( chngRowid ){      i = 0;    }else{      for(i=0; i<pIdx->nColumn; i++){        if( aXRef[pIdx->aiColumn[i]]>=0 ) break;      }    }    if( i<pIdx->nColumn ){      apIdx[nIdx++] = pIdx;      aIdxUsed[j] = 1;    }else{      aIdxUsed[j] = 0;    }  }  /* Begin generating code.  */  v = sqlite3GetVdbe(pParse);  if( v==0 ) goto update_cleanup;  if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);  sqlite3BeginWriteOperation(pParse, 1, iDb);#ifndef SQLITE_OMIT_VIRTUALTABLE  /* Virtual tables must be handled separately */  if( IsVirtual(pTab) ){    updateVirtualTable(pParse, pTabList, pTab, pChanges, pRowidExpr, aXRef,                       pWhere);    pWhere = 0;    pTabList = 0;    goto update_cleanup;  }#endif  /* Resolve the column names in all the expressions in the  ** WHERE clause.  */  if( sqlite3ExprResolveNames(&sNC, pWhere) ){    goto update_cleanup;  }  /* Start the view context  */  if( isView ){    sqlite3AuthContextPush(pParse, &sContext, pTab->zName);  }  /* If we are trying to update a view, realize that view into  ** a ephemeral table.  */  if( isView ){    Select *pView;    pView = sqlite3SelectDup(pTab->pSelect);    sqlite3Select(pParse, pView, SRT_EphemTab, iCur, 0, 0, 0, 0);    sqlite3SelectDelete(pView);  }  /* Begin the database scan  */  pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0);  if( pWInfo==0 ) goto update_cleanup;  /* Remember the rowid of every item to be updated.  */  sqlite3VdbeAddOp(v, IsVirtual(pTab) ? OP_VRowid : OP_Rowid, iCur, 0);  sqlite3VdbeAddOp(v, OP_FifoWrite, 0, 0);  /* End the database scan loop.  */  sqlite3WhereEnd(pWInfo);  /* Initialize the count of updated rows  */