/*

 ** 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

 ** in order to generate code for DELETE FROM statements.

 **

 ** $Id: delete.c,v 1.171 2008/07/28 19:34:53 drh Exp $

 */

 #include "sqliteInt.h"

 /*

 ** Look up every table that is named in pSrc.  If any table is not found,

 ** add an error message to pParse->zErrMsg and return NULL.  If all tables

 ** are found, return a pointer to the last table.

 */

 Table *sqlite3SrcListLookup(Parse *pParse, SrcList *pSrc){

   Table *pTab = 0;

   int i;

   struct SrcList_item *pItem;

   for(i=0, pItem=pSrc->a; i<pSrc->nSrc; i++, pItem++){

     pTab = sqlite3LocateTable(pParse, 0, pItem->zName, pItem->zDatabase);

     sqlite3DeleteTable(pItem->pTab);

     pItem->pTab = pTab;

     if( pTab ){

       pTab->nRef++;

     }

   }

   return pTab;

 }

 /*

 ** Check to make sure the given table is writable.  If it is not

 ** writable, generate an error message and return 1.  If it is

 ** writable return 0;

 */

 int sqlite3IsReadOnly(Parse *pParse, Table *pTab, int viewOk){

   if( (pTab->readOnly && (pParse->db->flags & SQLITE_WriteSchema)==0

         && pParse->nested==0) 

 #ifndef SQLITE_OMIT_VIRTUALTABLE

       || (pTab->pMod && pTab->pMod->pModule->xUpdate==0)

 #endif

   ){

     sqlite3ErrorMsg(pParse, "table %s may not be modified", pTab->zName);

     return 1;

   }

 #ifndef SQLITE_OMIT_VIEW

   if( !viewOk && pTab->pSelect ){

     sqlite3ErrorMsg(pParse,"cannot modify %s because it is a view",pTab->zName);

     return 1;

   }

 #endif

   return 0;

 }

 /*

 ** Generate code that will open a table for reading.

 */

 void sqlite3OpenTable(

   Parse *p,       /* Generate code into this VDBE */

   int iCur,       /* The cursor number of the table */

   int iDb,        /* The database index in sqlite3.aDb[] */

   Table *pTab,    /* The table to be opened */

   int opcode      /* OP_OpenRead or OP_OpenWrite */

 ){

   Vdbe *v;

   if( IsVirtual(pTab) ) return;

   v = sqlite3GetVdbe(p);

   assert( opcode==OP_OpenWrite || opcode==OP_OpenRead );

   sqlite3TableLock(p, iDb, pTab->tnum, (opcode==OP_OpenWrite), pTab->zName);

   sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, pTab->nCol);

   sqlite3VdbeAddOp3(v, opcode, iCur, pTab->tnum, iDb);

   VdbeComment((v, "%s", pTab->zName));

 }

 #if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)

 /*

 ** Evaluate a view and store its result in an ephemeral table.  The

 ** pWhere argument is an optional WHERE clause that restricts the

 ** set of rows in the view that are to be added to the ephemeral table.

 */

 void sqlite3MaterializeView(

   Parse *pParse,       /* Parsing context */

   Select *pView,       /* View definition */

   Expr *pWhere,        /* Optional WHERE clause to be added */

   int iCur             /* Cursor number for ephemerial table */

 ){

   SelectDest dest;

   Select *pDup;

   sqlite3 *db = pParse->db;

   pDup = sqlite3SelectDup(db, pView);

   if( pWhere ){

     SrcList *pFrom;

     pWhere = sqlite3ExprDup(db, pWhere);

     pFrom = sqlite3SrcListAppendFromTerm(pParse, 0, 0, 0, 0, pDup, 0, 0);

     pDup = sqlite3SelectNew(pParse, 0, pFrom, pWhere, 0, 0, 0, 0, 0, 0);

   }

   sqlite3SelectDestInit(&dest, SRT_EphemTab, iCur);

   sqlite3Select(pParse, pDup, &dest, 0, 0, 0);

   sqlite3SelectDelete(db, pDup);

 }

 #endif /* !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER) */

 /*

 ** Generate code for a DELETE FROM statement.

 **

 **     DELETE FROM table_wxyz WHERE a<5 AND b NOT NULL;

 **                 \________/       \________________/

 **                  pTabList              pWhere

 */

 void sqlite3DeleteFrom(

   Parse *pParse,         /* The parser context */

   SrcList *pTabList,     /* The table from which we should delete things */

   Expr *pWhere           /* The WHERE clause.  May be null */

 ){

   Vdbe *v;               /* The virtual database engine */

   Table *pTab;           /* The table from which records will be deleted */

   const char *zDb;       /* Name of database holding pTab */

   int end, addr = 0;     /* A couple addresses of generated code */

   int i;                 /* Loop counter */

   WhereInfo *pWInfo;     /* Information about the WHERE clause */

   Index *pIdx;           /* For looping over indices of the table */

   int iCur;              /* VDBE Cursor number for pTab */

   sqlite3 *db;           /* Main database structure */

   AuthContext sContext;  /* Authorization context */

   int oldIdx = -1;       /* Cursor for the OLD table of AFTER triggers */

   NameContext sNC;       /* Name context to resolve expressions in */

   int iDb;               /* Database number */

   int memCnt = 0;        /* Memory cell used for change counting */

 #ifndef SQLITE_OMIT_TRIGGER

   int isView;                  /* True if attempting to delete from a view */

   int triggers_exist = 0;      /* True if any triggers exist */

 #endif

   int iBeginAfterTrigger = 0;  /* Address of after trigger program */

   int iEndAfterTrigger = 0;    /* Exit of after trigger program */

   int iBeginBeforeTrigger = 0; /* Address of before trigger program */

   int iEndBeforeTrigger = 0;   /* Exit of before trigger program */

   u32 old_col_mask = 0;        /* Mask of OLD.* columns in use */

   sContext.pParse = 0;

   db = pParse->db;

   if( pParse->nErr || db->mallocFailed ){

     goto delete_from_cleanup;

   }

   assert( pTabList->nSrc==1 );

   /* Locate the table which we want to delete.  This table has to be

   ** put in an SrcList structure because some of the subroutines we

   ** will be calling are designed to work with multiple tables and expect

   ** an SrcList* parameter instead of just a Table* parameter.

   */

   pTab = sqlite3SrcListLookup(pParse, pTabList);

   if( pTab==0 )  goto delete_from_cleanup;

   /* Figure out if we have any triggers and if the table being

   ** deleted from is a view

   */

 #ifndef SQLITE_OMIT_TRIGGER

   triggers_exist = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0);

   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 delete_from_cleanup;

   }

   iDb = sqlite3SchemaToIndex(db, pTab->pSchema);

   assert( iDb<db->nDb );

   zDb = db->aDb[iDb].zName;

   if( sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb) ){

     goto delete_from_cleanup;

   }

   /* If pTab is really a view, make sure it has been initialized.

   */

   if( sqlite3ViewGetColumnNames(pParse, pTab) ){

     goto delete_from_cleanup;

   }

   /* Allocate a cursor used to store the old.* data for a trigger.

   */

   if( triggers_exist ){ 

     oldIdx = pParse->nTab++;

   }

   /* Assign  cursor number to the table and all its indices.

   */

   assert( pTabList->nSrc==1 );

   iCur = pTabList->a[0].iCursor = pParse->nTab++;

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

     pParse->nTab++;

   }

   /* Start the view context

   */

   if( isView ){

     sqlite3AuthContextPush(pParse, &sContext, pTab->zName);

   }

   /* Begin generating code.

   */

   v = sqlite3GetVdbe(pParse);

   if( v==0 ){

     goto delete_from_cleanup;

   }

   if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);

   sqlite3BeginWriteOperation(pParse, triggers_exist, iDb);

   if( triggers_exist ){

     int orconf = ((pParse->trigStack)?pParse->trigStack->orconf:OE_Default);

     int iGoto = sqlite3VdbeAddOp0(v, OP_Goto);

     addr = sqlite3VdbeMakeLabel(v);

     iBeginBeforeTrigger = sqlite3VdbeCurrentAddr(v);

     (void)sqlite3CodeRowTrigger(pParse, TK_DELETE, 0, TRIGGER_BEFORE, pTab,

         -1, oldIdx, orconf, addr, &old_col_mask, 0);

     iEndBeforeTrigger = sqlite3VdbeAddOp0(v, OP_Goto);

     iBeginAfterTrigger = sqlite3VdbeCurrentAddr(v);

     (void)sqlite3CodeRowTrigger(pParse, TK_DELETE, 0, TRIGGER_AFTER, pTab, -1,

         oldIdx, orconf, addr, &old_col_mask, 0);

     iEndAfterTrigger = sqlite3VdbeAddOp0(v, OP_Goto);

     sqlite3VdbeJumpHere(v, iGoto);

   }

   /* If we are trying to delete from a view, realize that view into

   ** a ephemeral table.

   */

   if( isView ){

     sqlite3MaterializeView(pParse, pTab->pSelect, pWhere, iCur);

   }

   /* Resolve the column names in the WHERE clause.

   */

   memset(&sNC, 0, sizeof(sNC));

   sNC.pParse = pParse;

   sNC.pSrcList = pTabList;

   if( sqlite3ExprResolveNames(&sNC, pWhere) ){

     goto delete_from_cleanup;

   }

   /* Initialize the counter of the number of rows deleted, if

   ** we are counting rows.

   */

   if( db->flags & SQLITE_CountRows ){

     memCnt = ++pParse->nMem;

     sqlite3VdbeAddOp2(v, OP_Integer, 0, memCnt);

   }

   /* Special case: A DELETE without a WHERE clause deletes everything.

   ** It is easier just to erase the whole table.  Note, however, that

   ** this means that the row change count will be incorrect.

   */

   if( pWhere==0 && !triggers_exist && !IsVirtual(pTab) ){

     if( db->flags & SQLITE_CountRows ){

       /* If counting rows deleted, just count the total number of

       ** entries in the table. */

       int addr2;

       if( !isView ){

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

       }

       sqlite3VdbeAddOp2(v, OP_Rewind, iCur, sqlite3VdbeCurrentAddr(v)+2);

       addr2 = sqlite3VdbeAddOp2(v, OP_AddImm, memCnt, 1);

       sqlite3VdbeAddOp2(v, OP_Next, iCur, addr2);

       sqlite3VdbeAddOp1(v, OP_Close, iCur);

     }

     if( !isView ){

       sqlite3VdbeAddOp2(v, OP_Clear, pTab->tnum, iDb);

       if( !pParse->nested ){

         sqlite3VdbeChangeP4(v, -1, pTab->zName, P4_STATIC);

       }

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

         assert( pIdx->pSchema==pTab->pSchema );

         sqlite3VdbeAddOp2(v, OP_Clear, pIdx->tnum, iDb);

       }

     }

   } 

   /* The usual case: There is a WHERE clause so we have to scan through

   ** the table and pick which records to delete.

   */

   else{

     int iRowid = ++pParse->nMem;    /* Used for storing rowid values. */

     /* Begin the database scan

     */

     pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0, 0);

     if( pWInfo==0 ) goto delete_from_cleanup;

     /* Remember the rowid of every item to be deleted.

     */

     sqlite3VdbeAddOp2(v, IsVirtual(pTab) ? OP_VRowid : OP_Rowid, iCur, iRowid);

     sqlite3VdbeAddOp1(v, OP_FifoWrite, iRowid);

     if( db->flags & SQLITE_CountRows ){

       sqlite3VdbeAddOp2(v, OP_AddImm, memCnt, 1);

     }

     /* End the database scan loop.

     */

     sqlite3WhereEnd(pWInfo);

     /* Open the pseudo-table used to store OLD if there are triggers.

     */

     if( triggers_exist ){

       sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, pTab->nCol);

       sqlite3VdbeAddOp1(v, OP_OpenPseudo, oldIdx);

     }

     /* Delete every item whose key was written to the list during the

     ** database scan.  We have to delete items after the scan is complete

     ** because deleting an item can change the scan order.

     */

     end = sqlite3VdbeMakeLabel(v);

     if( !isView ){

       /* Open cursors for the table we are deleting from and 

       ** all its indices.

       */

       sqlite3OpenTableAndIndices(pParse, pTab, iCur, OP_OpenWrite);

     }

     /* This is the beginning of the delete loop. If a trigger encounters

     ** an IGNORE constraint, it jumps back to here.

     */

     if( triggers_exist ){

       sqlite3VdbeResolveLabel(v, addr);

     }

     addr = sqlite3VdbeAddOp2(v, OP_FifoRead, iRowid, end);

     if( triggers_exist ){

       int iData = ++pParse->nMem;   /* For storing row data of OLD table */

       /* If the record is no longer present in the table, jump to the

       ** next iteration of the loop through the contents of the fifo.

       */

       sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addr, iRowid);

       /* Populate the OLD.* pseudo-table */

       if( old_col_mask ){

         sqlite3VdbeAddOp2(v, OP_RowData, iCur, iData);

       }else{

         sqlite3VdbeAddOp2(v, OP_Null, 0, iData);

       }

       sqlite3VdbeAddOp3(v, OP_Insert, oldIdx, iData, iRowid);

       /* Jump back and run the BEFORE triggers */

       sqlite3VdbeAddOp2(v, OP_Goto, 0, iBeginBeforeTrigger);

       sqlite3VdbeJumpHere(v, iEndBeforeTrigger);

     }

     if( !isView ){

       /* Delete the row */

 #ifndef SQLITE_OMIT_VIRTUALTABLE

       if( IsVirtual(pTab) ){

         const char *pVtab = (const char *)pTab->pVtab;

         sqlite3VtabMakeWritable(pParse, pTab);

         sqlite3VdbeAddOp4(v, OP_VUpdate, 0, 1, iRowid, pVtab, P4_VTAB);

       }else

 #endif

       {

         sqlite3GenerateRowDelete(pParse, pTab, iCur, iRowid, pParse->nested==0);

       }

     }

     /* If there are row triggers, close all cursors then invoke

     ** the AFTER triggers

     */

     if( triggers_exist ){

       /* Jump back and run the AFTER triggers */

       sqlite3VdbeAddOp2(v, OP_Goto, 0, iBeginAfterTrigger);

       sqlite3VdbeJumpHere(v, iEndAfterTrigger);

     }

     /* End of the delete loop */

     sqlite3VdbeAddOp2(v, OP_Goto, 0, addr);

     sqlite3VdbeResolveLabel(v, end);

     /* Close the cursors after the loop if there are no row triggers */

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

       for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){

         sqlite3VdbeAddOp2(v, OP_Close, iCur + i, pIdx->tnum);

       }

       sqlite3VdbeAddOp1(v, OP_Close, iCur);

     }

   }

   /*

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

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

   ** invoke the callback function.

   */

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

     sqlite3VdbeAddOp2(v, OP_ResultRow, memCnt, 1);

     sqlite3VdbeSetNumCols(v, 1);

     sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows deleted", P4_STATIC);

   }

 delete_from_cleanup:

   sqlite3AuthContextPop(&sContext);

   sqlite3SrcListDelete(db, pTabList);

   sqlite3ExprDelete(db, pWhere);

   return;

 }

 /*

 ** This routine generates VDBE code that causes a single row of a

 ** single table to be deleted.

 **

 ** The VDBE must be in a particular state when this routine is called.

 ** These are the requirements:

 **

 **   1.  A read/write cursor pointing to pTab, the table containing the row

 **       to be deleted, must be opened as cursor number "base".

 **

 **   2.  Read/write cursors for all indices of pTab must be open as

 **       cursor number base+i for the i-th index.

 **

 **   3.  The record number of the row to be deleted must be stored in

 **       memory cell iRowid.

 **

 ** This routine pops the top of the stack to remove the record number

 ** and then generates code to remove both the table record and all index

 ** entries that point to that record.

 */

 void sqlite3GenerateRowDelete(

   Parse *pParse,     /* Parsing context */

   Table *pTab,       /* Table containing the row to be deleted */

   int iCur,          /* Cursor number for the table */

   int iRowid,        /* Memory cell that contains the rowid to delete */

   int count          /* Increment the row change counter */

 ){

   int addr;

   Vdbe *v;

   v = pParse->pVdbe;

   addr = sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, iRowid);

   sqlite3GenerateRowIndexDelete(pParse, pTab, iCur, 0);

   sqlite3VdbeAddOp2(v, OP_Delete, iCur, (count?OPFLAG_NCHANGE:0));

   if( count ){

     sqlite3VdbeChangeP4(v, -1, pTab->zName, P4_STATIC);

   }

   sqlite3VdbeJumpHere(v, addr);

 }

 /*

 ** This routine generates VDBE code that causes the deletion of all

 ** index entries associated with a single row of a single table.

 **

 ** The VDBE must be in a particular state when this routine is called.

 ** These are the requirements:

 **

 **   1.  A read/write cursor pointing to pTab, the table containing the row

 **       to be deleted, must be opened as cursor number "iCur".

 **

 **   2.  Read/write cursors for all indices of pTab must be open as

 **       cursor number iCur+i for the i-th index.

 **

 **   3.  The "iCur" cursor must be pointing to the row that is to be

 **       deleted.

 */

 void sqlite3GenerateRowIndexDelete(

   Parse *pParse,     /* Parsing and code generating context */

   Table *pTab,       /* Table containing the row to be deleted */

   int iCur,          /* Cursor number for the table */

   int *aRegIdx       /* Only delete if aRegIdx!=0 && aRegIdx[i]>0 */

 ){

   int i;

   Index *pIdx;

   int r1;

   for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){

     if( aRegIdx!=0 && aRegIdx[i-1]==0 ) continue;

     r1 = sqlite3GenerateIndexKey(pParse, pIdx, iCur, 0, 0);

     sqlite3VdbeAddOp3(pParse->pVdbe, OP_IdxDelete, iCur+i, r1,pIdx->nColumn+1);

   }

 }

 /*

 ** Generate code that will assemble an index key and put it in register

 ** regOut.  The key with be for index pIdx which is an index on pTab.

 ** iCur is the index of a cursor open on the pTab table and pointing to

 ** the entry that needs indexing.

 **

 ** Return a register number which is the first in a block of

 ** registers that holds the elements of the index key.  The

 ** block of registers has already been deallocated by the time

 ** this routine returns.

 */

 int sqlite3GenerateIndexKey(

   Parse *pParse,     /* Parsing context */

   Index *pIdx,       /* The index for which to generate a key */

   int iCur,          /* Cursor number for the pIdx->pTable table */

   int regOut,        /* Write the new index key to this register */

   int doMakeRec      /* Run the OP_MakeRecord instruction if true */

 ){

   Vdbe *v = pParse->pVdbe;

   int j;

   Table *pTab = pIdx->pTable;

   int regBase;

   int nCol;

   nCol = pIdx->nColumn;

   regBase = sqlite3GetTempRange(pParse, nCol+1);

   sqlite3VdbeAddOp2(v, OP_Rowid, iCur, regBase+nCol);

   for(j=0; j<nCol; j++){

     int idx = pIdx->aiColumn[j];

     if( idx==pTab->iPKey ){

       sqlite3VdbeAddOp2(v, OP_SCopy, regBase+nCol, regBase+j);

     }else{

       sqlite3VdbeAddOp3(v, OP_Column, iCur, idx, regBase+j);

       sqlite3ColumnDefault(v, pTab, idx);

     }

   }

   if( doMakeRec ){

     sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol+1, regOut);

     sqlite3IndexAffinityStr(v, pIdx);

     sqlite3ExprCacheAffinityChange(pParse, regBase, nCol+1);

   }

   sqlite3ReleaseTempRange(pParse, regBase, nCol+1);

   return regBase;

 }

 /* Make sure "isView" gets undefined in case this file becomes part of

 ** the amalgamation - so that subsequent files do not see isView as a

 ** macro. */

 #undef isView