delete.c

最新的sqlite3.6.2源代码

  */
  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