update.c

最新的sqlite3.6.2源代码

  /* Begin the database scan
  */
  sqlite3VdbeAddOp2(v, OP_Null, 0, regOldRowid);
  pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0,
                             WHERE_ONEPASS_DESIRED);
  if( pWInfo==0 ) goto update_cleanup;
  okOnePass = pWInfo->okOnePass;

  /* Remember the rowid of every item to be updated.
  */
  sqlite3VdbeAddOp2(v, IsVirtual(pTab)?OP_VRowid:OP_Rowid, iCur, regOldRowid);
  if( !okOnePass ) sqlite3VdbeAddOp2(v, OP_FifoWrite, regOldRowid, 0);

  /* End the database scan loop.
  */
  sqlite3WhereEnd(pWInfo);

  /* Initialize the count of updated rows
  */
  if( db->flags & SQLITE_CountRows && !pParse->trigStack ){
    regRowCount = ++pParse->nMem;
    sqlite3VdbeAddOp2(v, OP_Integer, 0, regRowCount);
  }

  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.
    */
    if( !okOnePass ) 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 || aRegIdx[i]>0 ){
        KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);
        sqlite3VdbeAddOp4(v, OP_OpenWrite, iCur+i+1, pIdx->tnum, iDb,
                       (char*)pKey, P4_KEYINFO_HANDOFF);
        assert( pParse->nTab>iCur+i+1 );
      }
    }
  }
  
  /* Jump back to this point if a trigger encounters an IGNORE constraint. */
  if( triggers_exist ){
    sqlite3VdbeResolveLabel(v, addr);
  }

  /* Top of the update loop */
  if( okOnePass ){
    int a1 = sqlite3VdbeAddOp1(v, OP_NotNull, regOldRowid);
    addr = sqlite3VdbeAddOp0(v, OP_Goto);
    sqlite3VdbeJumpHere(v, a1);
  }else{
    addr = sqlite3VdbeAddOp2(v, OP_FifoRead, regOldRowid, 0);
  }

  if( triggers_exist ){
    int regRowid;
    int regRow;
    int regCols;

    /* Make cursor iCur point to the record that is being updated.
    */
    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addr, regOldRowid);

    /* Generate the OLD table
    */
    regRowid = sqlite3GetTempReg(pParse);
    regRow = sqlite3GetTempReg(pParse);
    sqlite3VdbeAddOp2(v, OP_Rowid, iCur, regRowid);
    if( !old_col_mask ){
      sqlite3VdbeAddOp2(v, OP_Null, 0, regRow);
    }else{
      sqlite3VdbeAddOp2(v, OP_RowData, iCur, regRow);
    }
    sqlite3VdbeAddOp3(v, OP_Insert, oldIdx, regRow, regRowid);

    /* Generate the NEW table
    */
    if( chngRowid ){
      sqlite3ExprCodeAndCache(pParse, pRowidExpr, regRowid);
    }else{
      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, regRowid);
    }
    regCols = sqlite3GetTempRange(pParse, pTab->nCol);
    for(i=0; i<pTab->nCol; i++){
      if( i==pTab->iPKey ){
        sqlite3VdbeAddOp2(v, OP_Null, 0, regCols+i);
        continue;
      }
      j = aXRef[i];
      if( new_col_mask&((u32)1<<i) || new_col_mask==0xffffffff ){
        if( j<0 ){
          sqlite3VdbeAddOp3(v, OP_Column, iCur, i, regCols+i);
          sqlite3ColumnDefault(v, pTab, i);
        }else{
          sqlite3ExprCodeAndCache(pParse, pChanges->a[j].pExpr, regCols+i);
        }
      }else{
        sqlite3VdbeAddOp2(v, OP_Null, 0, regCols+i);
      }
    }
    sqlite3VdbeAddOp3(v, OP_MakeRecord, regCols, pTab->nCol, regRow);
    if( !isView ){
      sqlite3TableAffinityStr(v, pTab);
      sqlite3ExprCacheAffinityChange(pParse, regCols, pTab->nCol);
    }
    sqlite3ReleaseTempRange(pParse, regCols, pTab->nCol);
    /* if( pParse->nErr ) goto update_cleanup; */
    sqlite3VdbeAddOp3(v, OP_Insert, newIdx, regRow, regRowid);
    sqlite3ReleaseTempReg(pParse, regRowid);
    sqlite3ReleaseTempReg(pParse, regRow);

    sqlite3VdbeAddOp2(v, OP_Goto, 0, iBeginBeforeTrigger);
    sqlite3VdbeJumpHere(v, iEndBeforeTrigger);
  }

  if( !isView && !IsVirtual(pTab) ){
    /* 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.
    */
    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addr, regOldRowid);

    /* 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, regNewRowid);
      sqlite3VdbeAddOp1(v, OP_MustBeInt, regNewRowid);
    }

    /* Compute new data for this record.  
    */
    for(i=0; i<pTab->nCol; i++){
      if( i==pTab->iPKey ){
        sqlite3VdbeAddOp2(v, OP_Null, 0, regData+i);
        continue;
      }
      j = aXRef[i];
      if( j<0 ){
        sqlite3VdbeAddOp3(v, OP_Column, iCur, i, regData+i);
        sqlite3ColumnDefault(v, pTab, i);
      }else{
        sqlite3ExprCode(pParse, pChanges->a[j].pExpr, regData+i);
      }
    }

    /* Do constraint checks
    */
    sqlite3GenerateConstraintChecks(pParse, pTab, iCur, regNewRowid,
                                    aRegIdx, chngRowid, 1,
                                    onError, addr);

    /* Delete the old indices for the current record.
    */
    j1 = sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, regOldRowid);
    sqlite3GenerateRowIndexDelete(pParse, pTab, iCur, aRegIdx);

    /* If changing the record number, delete the old record.
    */
    if( chngRowid ){
      sqlite3VdbeAddOp2(v, OP_Delete, iCur, 0);
    }
    sqlite3VdbeJumpHere(v, j1);

    /* Create the new index entries and the new record.
    */
    sqlite3CompleteInsertion(pParse, pTab, iCur, regNewRowid, 
                             aRegIdx, chngRowid, 1, -1, 0);
  }

  /* Increment the row counter 
  */
  if( db->flags & SQLITE_CountRows && !pParse->trigStack){
    sqlite3VdbeAddOp2(v, OP_AddImm, regRowCount, 1);
  }

  /* If there are triggers, close all the cursors after each iteration
  ** through the loop.  The fire the after triggers.
  */
  if( triggers_exist ){
    sqlite3VdbeAddOp2(v, OP_Goto, 0, iBeginAfterTrigger);
    sqlite3VdbeJumpHere(v, iEndAfterTrigger);
  }

  /* Repeat the above with the next record to be updated, until
  ** all record selected by the WHERE clause have been updated.
  */
  sqlite3VdbeAddOp2(v, OP_Goto, 0, addr);
  sqlite3VdbeJumpHere(v, addr);

  /* Close all tables */
  for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
    if( openAll || aRegIdx[i]>0 ){
      sqlite3VdbeAddOp2(v, OP_Close, iCur+i+1, 0);
    }
  }
  sqlite3VdbeAddOp2(v, OP_Close, iCur, 0);
  if( triggers_exist ){
    sqlite3VdbeAddOp2(v, OP_Close, newIdx, 0);
    sqlite3VdbeAddOp2(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 ){
    sqlite3VdbeAddOp2(v, OP_ResultRow, regRowCount, 1);
    sqlite3VdbeSetNumCols(v, 1);
    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows updated", P4_STATIC);
  }

update_cleanup:
  sqlite3AuthContextPop(&sContext);
  sqlite3DbFree(db, aRegIdx);
  sqlite3DbFree(db, aXRef);
  sqlite3SrcListDelete(db, pTabList);
  sqlite3ExprListDelete(db, pChanges);
  sqlite3ExprDelete(db, pWhere);
  return;
}

#ifndef SQLITE_OMIT_VIRTUALTABLE
/*
** Generate code for an UPDATE of a virtual table.
**
** The strategy is that we create an ephemerial table that contains
** for each row to be changed:
**
**   (A)  The original rowid of that row.
**   (B)  The revised rowid for the row. (note1)
**   (C)  The content of every column in the row.
**
** Then we loop over this ephemeral table and for each row in
** the ephermeral table call VUpdate.
**
** When finished, drop the ephemeral table.
**
** (note1) Actually, if we know in advance that (A) is always the same
** as (B) we only store (A), then duplicate (A) when pulling
** it out of the ephemeral table before calling VUpdate.
*/
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 *pRowid,        /* 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 */
){
  Vdbe *v = pParse->pVdbe;  /* Virtual machine under construction */
  ExprList *pEList = 0;     /* The result set of the SELECT statement */
  Select *pSelect = 0;      /* The SELECT statement */
  Expr *pExpr;              /* Temporary expression */
  int ephemTab;             /* Table holding the result of the SELECT */
  int i;                    /* Loop counter */
  int addr;                 /* Address of top of loop */
  int iReg;                 /* First register in set passed to OP_VUpdate */
  sqlite3 *db = pParse->db; /* Database connection */
  const char *pVtab = (const char*)pTab->pVtab;
  SelectDest dest;

  /* Construct the SELECT statement that will find the new values for
  ** all updated rows. 
  */
  pEList = sqlite3ExprListAppend(pParse, 0, 
                                 sqlite3CreateIdExpr(pParse, "_rowid_"), 0);
  if( pRowid ){
    pEList = sqlite3ExprListAppend(pParse, pEList,
                                   sqlite3ExprDup(db, pRowid), 0);
  }
  assert( pTab->iPKey<0 );
  for(i=0; i<pTab->nCol; i++){
    if( aXRef[i]>=0 ){
      pExpr = sqlite3ExprDup(db, pChanges->a[aXRef[i]].pExpr);
    }else{
      pExpr = sqlite3CreateIdExpr(pParse, pTab->aCol[i].zName);
    }
    pEList = sqlite3ExprListAppend(pParse, pEList, pExpr, 0);
  }
  pSelect = sqlite3SelectNew(pParse, pEList, pSrc, pWhere, 0, 0, 0, 0, 0, 0);
  
  /* Create the ephemeral table into which the update results will
  ** be stored.
  */
  assert( v );
  ephemTab = pParse->nTab++;
  sqlite3VdbeAddOp2(v, OP_OpenEphemeral, ephemTab, pTab->nCol+1+(pRowid!=0));

  /* fill the ephemeral table 
  */
  sqlite3SelectDestInit(&dest, SRT_Table, ephemTab);
  sqlite3Select(pParse, pSelect, &dest);

  /* Generate code to scan the ephemeral table and call VUpdate. */
  iReg = ++pParse->nMem;
  pParse->nMem += pTab->nCol+1;
  sqlite3VdbeAddOp2(v, OP_Rewind, ephemTab, 0);
  addr = sqlite3VdbeCurrentAddr(v);
  sqlite3VdbeAddOp3(v, OP_Column,  ephemTab, 0, iReg);
  sqlite3VdbeAddOp3(v, OP_Column, ephemTab, (pRowid?1:0), iReg+1);
  for(i=0; i<pTab->nCol; i++){
    sqlite3VdbeAddOp3(v, OP_Column, ephemTab, i+1+(pRowid!=0), iReg+2+i);
  }
  sqlite3VtabMakeWritable(pParse, pTab);
  sqlite3VdbeAddOp4(v, OP_VUpdate, 0, pTab->nCol+2, iReg, pVtab, P4_VTAB);
  sqlite3VdbeAddOp2(v, OP_Next, ephemTab, addr);
  sqlite3VdbeJumpHere(v, addr-1);
  sqlite3VdbeAddOp2(v, OP_Close, ephemTab, 0);

  /* Cleanup */
  sqlite3SelectDelete(db, pSelect);  
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */

/* 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