/*** 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 1.122 2006/02/24 02:53:50 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, pItem->zName, pItem->zDatabase);    sqlite3DeleteTable(pParse->db, 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 ){    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 = sqlite3GetVdbe(p);  assert( opcode==OP_OpenWrite || opcode==OP_OpenRead );  sqlite3TableLock(p, iDb, pTab->tnum, (opcode==OP_OpenWrite), pTab->zName);  sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);  VdbeComment((v, "# %s", pTab->zName));  sqlite3VdbeAddOp(v, opcode, iCur, pTab->tnum);  sqlite3VdbeAddOp(v, OP_SetNumColumns, iCur, pTab->nCol);}/*** 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;#ifndef SQLITE_OMIT_TRIGGER  int isView;                  /* True if attempting to delete from a view */  int triggers_exist = 0;      /* True if any triggers exist */#endif  sContext.pParse = 0;  if( pParse->nErr || sqlite3MallocFailed() ){    goto delete_from_cleanup;  }  db = pParse->db;  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( isView && 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++;  }  /* Resolve the column names in the WHERE clause.  */  assert( pTabList->nSrc==1 );  iCur = pTabList->a[0].iCursor = pParse->nTab++;  memset(&sNC, 0, sizeof(sNC));  sNC.pParse = pParse;  sNC.pSrcList = pTabList;  if( sqlite3ExprResolveNames(&sNC, pWhere) ){    goto delete_from_cleanup;  }  /* 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 we are trying to delete from a view, realize that view into  ** a ephemeral table.  */  if( isView ){    Select *pView = sqlite3SelectDup(pTab->pSelect);    sqlite3Select(pParse, pView, SRT_VirtualTab, iCur, 0, 0, 0, 0);    sqlite3SelectDelete(pView);  }  /* Initialize the counter of the number of rows deleted, if  ** we are counting rows.  */  if( db->flags & SQLITE_CountRows ){    sqlite3VdbeAddOp(v, OP_Integer, 0, 0);  }  /* 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 ){    if( db->flags & SQLITE_CountRows ){      /* If counting rows deleted, just count the total number of      ** entries in the table. */      int endOfLoop = sqlite3VdbeMakeLabel(v);      int addr2;      if( !isView ){        sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);      }      sqlite3VdbeAddOp(v, OP_Rewind, iCur, sqlite3VdbeCurrentAddr(v)+2);      addr2 = sqlite3VdbeAddOp(v, OP_AddImm, 1, 0);      sqlite3VdbeAddOp(v, OP_Next, iCur, addr2);      sqlite3VdbeResolveLabel(v, endOfLoop);      sqlite3VdbeAddOp(v, OP_Close, iCur, 0);    }    if( !isView ){      sqlite3VdbeAddOp(v, OP_Clear, pTab->tnum, iDb);      if( !pParse->nested ){        sqlite3VdbeChangeP3(v, -1, pTab->zName, P3_STATIC);      }      for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){        assert( pIdx->pSchema==pTab->pSchema );        sqlite3VdbeAddOp(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{    /* Begin the database scan    */    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0);    if( pWInfo==0 ) goto delete_from_cleanup;    /* Remember the rowid of every item to be deleted.    */    sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);    sqlite3VdbeAddOp(v, OP_FifoWrite, 0, 0);    if( db->flags & SQLITE_CountRows ){      sqlite3VdbeAddOp(v, OP_AddImm, 1, 0);    }    /* End the database scan loop.    */    sqlite3WhereEnd(pWInfo);    /* Open the pseudo-table used to store OLD if there are triggers.    */    if( triggers_exist ){      sqlite3VdbeAddOp(v, OP_OpenPseudo, oldIdx, 0);      sqlite3VdbeAddOp(v, OP_SetNumColumns, oldIdx, pTab->nCol);    }    /* 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);    /* This is the beginning of the delete loop when there are    ** row triggers.    */    if( triggers_exist ){      addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, end);      if( !isView ){        sqlite3VdbeAddOp(v, OP_Dup, 0, 0);        sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);      }      sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);      sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);      sqlite3VdbeAddOp(v, OP_RowData, iCur, 0);      sqlite3VdbeAddOp(v, OP_Insert, oldIdx, 0);      if( !isView ){        sqlite3VdbeAddOp(v, OP_Close, iCur, 0);      }      (void)sqlite3CodeRowTrigger(pParse, TK_DELETE, 0, TRIGGER_BEFORE, pTab,          -1, oldIdx, (pParse->trigStack)?pParse->trigStack->orconf:OE_Default,          addr);    }    if( !isView ){      /* Open cursors for the table we are deleting from and all its      ** indices.  If there are row triggers, this happens inside the      ** OP_FifoRead loop because the cursor have to all be closed      ** before the trigger fires.  If there are no row triggers, the      ** cursors are opened only once on the outside the loop.      */      sqlite3OpenTableAndIndices(pParse, pTab, iCur, OP_OpenWrite);      /* This is the beginning of the delete loop when there are no      ** row triggers */      if( !triggers_exist ){         addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, end);      }      /* Delete the row */      sqlite3GenerateRowDelete(db, v, pTab, iCur, pParse->nested==0);    }    /* If there are row triggers, close all cursors then invoke    ** the AFTER triggers    */    if( triggers_exist ){      if( !isView ){        for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){          sqlite3VdbeAddOp(v, OP_Close, iCur + i, pIdx->tnum);        }        sqlite3VdbeAddOp(v, OP_Close, iCur, 0);      }      (void)sqlite3CodeRowTrigger(pParse, TK_DELETE, 0, TRIGGER_AFTER, pTab, -1,          oldIdx, (pParse->trigStack)?pParse->trigStack->orconf:OE_Default,          addr);    }    /* End of the delete loop */    sqlite3VdbeAddOp(v, OP_Goto, 0, addr);    sqlite3VdbeResolveLabel(v, end);    /* Close the cursors after the loop if there are no row triggers */    if( !triggers_exist ){      for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){        sqlite3VdbeAddOp(v, OP_Close, iCur + i, pIdx->tnum);      }      sqlite3VdbeAddOp(v, OP_Close, iCur, 0);    }  }  /*  ** 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 ){    sqlite3VdbeAddOp(v, OP_Callback, 1, 0);    sqlite3VdbeSetNumCols(v, 1);    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows deleted", P3_STATIC);  }delete_from_cleanup:  sqlite3AuthContextPop(&sContext);  sqlite3SrcListDelete(pTabList);  sqlite3ExprDelete(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 on the top**       of the stack.**** 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(  sqlite3 *db,       /* The database containing the index */  Vdbe *v,           /* Generate code into this VDBE */  Table *pTab,       /* Table containing the row to be deleted */  int iCur,          /* Cursor number for the table */  int count          /* Increment the row change counter */){  int addr;  addr = sqlite3VdbeAddOp(v, OP_NotExists, iCur, 0);  sqlite3GenerateRowIndexDelete(v, pTab, iCur, 0);  sqlite3VdbeAddOp(v, OP_Delete, iCur, (count?OPFLAG_NCHANGE:0));  if( count ){    sqlite3VdbeChangeP3(v, -1, pTab->zName, P3_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(  Vdbe *v,           /* Generate code into this VDBE */  Table *pTab,       /* Table containing the row to be deleted */  int iCur,          /* Cursor number for the table */  char *aIdxUsed     /* Only delete if aIdxUsed!=0 && aIdxUsed[i]!=0 */){  int i;  Index *pIdx;  for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){    if( aIdxUsed!=0 && aIdxUsed[i-1]==0 ) continue;    sqlite3GenerateIndexKey(v, pIdx, iCur);    sqlite3VdbeAddOp(v, OP_IdxDelete, iCur+i, 0);  }}/*** Generate code that will assemble an index key and put it on the top** of the tack.  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.*/void sqlite3GenerateIndexKey(  Vdbe *v,           /* Generate code into this VDBE */  Index *pIdx,       /* The index for which to generate a key */  int iCur           /* Cursor number for the pIdx->pTable table */){  int j;  Table *pTab = pIdx->pTable;  sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);  for(j=0; j<pIdx->nColumn; j++){    int idx = pIdx->aiColumn[j];    if( idx==pTab->iPKey ){      sqlite3VdbeAddOp(v, OP_Dup, j, 0);    }else{      sqlite3VdbeAddOp(v, OP_Column, iCur, idx);      sqlite3ColumnDefault(v, pTab, idx);    }  }  sqlite3VdbeAddOp(v, OP_MakeIdxRec, pIdx->nColumn, 0);  sqlite3IndexAffinityStr(v, pIdx);}