/*

** 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

  */

  if( db->flags & SQLITE_CountRows && !pParse->trigStack ){

    sqlite3VdbeAddOp(v, OP_Integer, 0, 0);

  }

  if( triggers_exist ){

    /* Create pseudo-tables for NEW and OLD

    */

    sqlite3VdbeAddOp(v, OP_OpenPseudo, oldIdx, 0);

    sqlite3VdbeAddOp(v, OP_SetNumColumns, oldIdx, pTab->nCol);

    sqlite3VdbeAddOp(v, OP_OpenPseudo, newIdx, 0);

    sqlite3VdbeAddOp(v, OP_SetNumColumns, newIdx, pTab->nCol);

    /* The top of the update loop for when there are triggers.

    */

    addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, 0);

    if( !isView ){

      sqlite3VdbeAddOp(v, OP_Dup, 0, 0);

      sqlite3VdbeAddOp(v, OP_Dup, 0, 0);

      /* Open a cursor and make it point to the record that is

      ** being updated.

      */

      sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);

    }

    sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);

    /* Generate the OLD table

    */

    sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);

    sqlite3VdbeAddOp(v, OP_RowData, iCur, 0);

    sqlite3VdbeAddOp(v, OP_Insert, oldIdx, 0);

    /* Generate the NEW table

    */

    if( chngRowid ){

      sqlite3ExprCodeAndCache(pParse, pRowidExpr);

    }else{

      sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);

    }

    for(i=0; i<pTab->nCol; i++){

      if( i==pTab->iPKey ){

        sqlite3VdbeAddOp(v, OP_Null, 0, 0);

        continue;

      }

      j = aXRef[i];

      if( j<0 ){

        sqlite3VdbeAddOp(v, OP_Column, iCur, i);

        sqlite3ColumnDefault(v, pTab, i);

      }else{

        sqlite3ExprCodeAndCache(pParse, pChanges->a[j].pExpr);

      }

    }

    sqlite3VdbeAddOp(v, OP_MakeRecord, pTab->nCol, 0);

    if( !isView ){

      sqlite3TableAffinityStr(v, pTab);

    }

    if( pParse->nErr ) goto update_cleanup;

    sqlite3VdbeAddOp(v, OP_Insert, newIdx, 0);

    if( !isView ){

      sqlite3VdbeAddOp(v, OP_Close, iCur, 0);

    }

    /* Fire the BEFORE and INSTEAD OF triggers

    */

    if( sqlite3CodeRowTrigger(pParse, TK_UPDATE, pChanges, TRIGGER_BEFORE, pTab,

          newIdx, oldIdx, onError, addr) ){

      goto update_cleanup;

    }

  }

  if( !isView && !IsVirtual(pTab) ){

    /* 

    ** Open every index that needs updating.  Note that if any

    ** index could potentially invoke a REPLACE conflict resolution 

    ** action, then we need to open all indices because we might need

    ** to be deleting some records.

    */

    sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenWrite); 

    if( onError==OE_Replace ){

      openAll = 1;

    }else{

      openAll = 0;

      for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){

        if( pIdx->onError==OE_Replace ){

          openAll = 1;

          break;

        }

      }

    }

    for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){

      if( openAll || aIdxUsed[i] ){

        KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);

        sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);

        sqlite3VdbeOp3(v, OP_OpenWrite, iCur+i+1, pIdx->tnum,

                       (char*)pKey, P3_KEYINFO_HANDOFF);

        assert( pParse->nTab>iCur+i+1 );

      }

    }

    /* Loop over every record that needs updating.  We have to load

    ** 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 entries.

    ** So make the cursor point at the old record.

    */

    if( !triggers_exist ){

      addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, 0);

      sqlite3VdbeAddOp(v, OP_Dup, 0, 0);

    }

    sqlite3VdbeAddOp(v, OP_NotExists, iCur, addr);

    /* 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( chngRowid ){

      sqlite3ExprCode(pParse, pRowidExpr);

      sqlite3VdbeAddOp(v, OP_MustBeInt, 0, 0);

    }

    /* Compute new data for this record.  

    */

    for(i=0; i<pTab->nCol; i++){

      if( i==pTab->iPKey ){

        sqlite3VdbeAddOp(v, OP_Null, 0, 0);

        continue;

      }

      j = aXRef[i];

      if( j<0 ){

        sqlite3VdbeAddOp(v, OP_Column, iCur, i);

        sqlite3ColumnDefault(v, pTab, i);

      }else{

        sqlite3ExprCode(pParse, pChanges->a[j].pExpr);

      }

    }

    /* Do constraint checks

    */

    sqlite3GenerateConstraintChecks(pParse, pTab, iCur, aIdxUsed, chngRowid, 1,

                                   onError, addr);

    /* Delete the old indices for the current record.

    */

    sqlite3GenerateRowIndexDelete(v, pTab, iCur, aIdxUsed);

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

    */

    if( chngRowid ){

      sqlite3VdbeAddOp(v, OP_Delete, iCur, 0);

    }

    /* Create the new index entries and the new record.

    */

    sqlite3CompleteInsertion(pParse, pTab, iCur, aIdxUsed, chngRowid, 1, -1);

  }

  /* Increment the row counter 

  */

  if( db->flags & SQLITE_CountRows && !pParse->trigStack){

    sqlite3VdbeAddOp(v, OP_AddImm, 1, 0);

  }

  /* If there are triggers, close all the cursors after each iteration

  ** through the loop.  The fire the after triggers.

  */

  if( triggers_exist ){

    if( !isView ){

      for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){

        if( openAll || aIdxUsed[i] )

          sqlite3VdbeAddOp(v, OP_Close, iCur+i+1, 0);

      }

      sqlite3VdbeAddOp(v, OP_Close, iCur, 0);

    }

    if( sqlite3CodeRowTrigger(pParse, TK_UPDATE, pChanges, TRIGGER_AFTER, pTab, 

          newIdx, oldIdx, onError, addr) ){

      goto update_cleanup;

    }

  }

  /* Repeat the above with the next record to be updated, until

  ** all record selected by the WHERE clause have been updated.

  */

  sqlite3VdbeAddOp(v, OP_Goto, 0, addr);

  sqlite3VdbeJumpHere(v, addr);

  /* Close all tables if there were no FOR EACH ROW triggers */

  if( !triggers_exist ){

    for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){

      if( openAll || aIdxUsed[i] ){

        sqlite3VdbeAddOp(v, OP_Close, iCur+i+1, 0);

      }

    }

    sqlite3VdbeAddOp(v, OP_Close, iCur, 0);

  }else{

    sqlite3VdbeAddOp(v, OP_Close, newIdx, 0);

    sqlite3VdbeAddOp(v, OP_Close, oldIdx, 0);

  }

  /*

  ** Return the number of rows that were changed. If this routine is 

  ** generating code because of a call to sqlite3NestedParse(), do not

  ** invoke the callback function.

  */

  if( db->flags & SQLITE_CountRows && !pParse->trigStack && pParse->nested==0 ){

    sqlite3VdbeAddOp(v, OP_Callback, 1, 0);

    sqlite3VdbeSetNumCols(v, 1);

    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows updated", P3_STATIC);

  }

update_cleanup:

  sqlite3AuthContextPop(&sContext);

  sqliteFree(apIdx);

  sqliteFree(aXRef);

  sqlite3SrcListDelete(pTabList);

  sqlite3ExprListDelete(pChanges);

  sqlite3ExprDelete(pWhere);