/*+
−
** 2001 September 15+
−
**+
−
** The author disclaims copyright to this source code.  In place of+
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** a legal notice, here is a blessing:+
−
**+
−
**    May you do good and not evil.+
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**    May you find forgiveness for yourself and forgive others.+
−
**    May you share freely, never taking more than you give.+
−
**+
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*************************************************************************+
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** This file contains C code routines that are called by the parser+
−
** in order to generate code for DELETE FROM statements.+
−
**+
−
** $Id: delete.cpp 1282 2008-11-13 09:31:33Z LarsPson $+
−
*/+
−
#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;+
−
  SrcList::SrcList_item *pItem;+
−
  for(i=0, pItem=pSrc->a; i<pSrc->nSrc; i++, pItem++){+
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    pTab = sqlite3LocateTable(pParse, pItem->zName, pItem->zDatabase);+
−
    sqlite3DeleteTable(pItem->pTab);+
−
    pItem->pTab = pTab;+
−
    if( pTab ){+
−
      pTab->nRef++;+
−
    }+
−
  }+
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  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+
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      || (pTab->pMod && pTab->pMod->pModule->xUpdate==0)+
−
#endif+
−
  ){+
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    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);+
−
  sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);+
−
  VdbeComment((v, "# %s", pTab->zName));+
−
  sqlite3VdbeAddOp(v, opcode, iCur, pTab->tnum);+
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  sqlite3VdbeAddOp(v, OP_SetNumColumns, iCur, pTab->nCol);+
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}+
−
+
−
+
−
/*+
−
** Generate code for a DELETE FROM statement.+
−
**+
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**     DELETE FROM table_wxyz WHERE a<5 AND b NOT NULL;+
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**                 \________/       \________________/+
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**                  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 */+
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  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+
−
+
−
  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++;+
−
  }+
−
+
−
  /* 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(db, pTab->pSelect);+
−
    sqlite3Select(pParse, pView, SRT_EphemTab, 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 ){+
−
    memCnt = pParse->nMem++;+
−
    sqlite3VdbeAddOp(v, OP_MemInt, 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);+
−
      }+
−
      sqlite3VdbeAddOp(v, OP_Rewind, iCur, sqlite3VdbeCurrentAddr(v)+2);+
−
      addr2 = sqlite3VdbeAddOp(v, OP_MemIncr, 1, memCnt);+
−
      sqlite3VdbeAddOp(v, OP_Next, iCur, addr2);+
−
      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, IsVirtual(pTab) ? OP_VRowid : OP_Rowid, iCur, 0);+
−
    sqlite3VdbeAddOp(v, OP_FifoWrite, 0, 0);+
−
    if( db->flags & SQLITE_CountRows ){+
−
      sqlite3VdbeAddOp(v, OP_MemIncr, 1, memCnt);+
−
    }+
−
+
−
    /* 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 ){+
−
      int mem1 = pParse->nMem++;+
−
      addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, end);+
−
      sqlite3VdbeAddOp(v, OP_StackDepth, -1, 0);+
−
      sqlite3VdbeAddOp(v, OP_MemStore, mem1, 0);+
−
      if( !isView ){+
−
        sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);+
−
      }+
−
      sqlite3VdbeAddOp(v, OP_NotExists, iCur, addr);+
−
      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 ){+
−
        sqlite3VdbeAddOp(v, OP_MemLoad, mem1, 0);+
−
      }+
−
    }+
−
+
−
    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);+
−
        sqlite3VdbeAddOp(v, OP_StackDepth, -1, 0);+
−
      }+
−
+
−
      /* Delete the row */+
−
#ifndef SQLITE_OMIT_VIRTUALTABLE+
−
      if( IsVirtual(pTab) ){+
−
        pParse->pVirtualLock = pTab;+
−
        sqlite3VdbeOp3(v, OP_VUpdate, 0, 1, (const char*)pTab->pVtab, P3_VTAB);+
−
      }else+
−
#endif+
−
      {+
−
        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 && !IsVirtual(pTab) ){+
−
      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_MemLoad, memCnt, 0);+
−
    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);+
−
}+
−