expr.c

一个小型嵌入式数据库SQLite的源码,C语言

    case TK_EXISTS:
#endif
    case TK_IN: {
      if( pExpr->pSelect ){
        int nRef = pNC->nRef;
#ifndef SQLITE_OMIT_CHECK
        if( pNC->isCheck ){
          sqlite3ErrorMsg(pParse,"subqueries prohibited in CHECK constraints");
        }
#endif
        sqlite3SelectResolve(pParse, pExpr->pSelect, pNC);
        assert( pNC->nRef>=nRef );
        if( nRef!=pNC->nRef ){
          ExprSetProperty(pExpr, EP_VarSelect);
        }
      }
      break;
    }
#ifndef SQLITE_OMIT_CHECK
    case TK_VARIABLE: {
      if( pNC->isCheck ){
        sqlite3ErrorMsg(pParse,"parameters prohibited in CHECK constraints");
      }
      break;
    }
#endif
  }
  return 0;
}

/*
** This routine walks an expression tree and resolves references to
** table columns.  Nodes of the form ID.ID or ID resolve into an
** index to the table in the table list and a column offset.  The 
** Expr.opcode for such nodes is changed to TK_COLUMN.  The Expr.iTable
** value is changed to the index of the referenced table in pTabList
** plus the "base" value.  The base value will ultimately become the
** VDBE cursor number for a cursor that is pointing into the referenced
** table.  The Expr.iColumn value is changed to the index of the column 
** of the referenced table.  The Expr.iColumn value for the special
** ROWID column is -1.  Any INTEGER PRIMARY KEY column is tried as an
** alias for ROWID.
**
** Also resolve function names and check the functions for proper
** usage.  Make sure all function names are recognized and all functions
** have the correct number of arguments.  Leave an error message
** in pParse->zErrMsg if anything is amiss.  Return the number of errors.
**
** If the expression contains aggregate functions then set the EP_Agg
** property on the expression.
*/
int sqlite3ExprResolveNames(
  NameContext *pNC,       /* Namespace to resolve expressions in. */
  Expr *pExpr             /* The expression to be analyzed. */
){
  int savedHasAgg;
  if( pExpr==0 ) return 0;
  savedHasAgg = pNC->hasAgg;
  pNC->hasAgg = 0;
  walkExprTree(pExpr, nameResolverStep, pNC);
  if( pNC->nErr>0 ){
    ExprSetProperty(pExpr, EP_Error);
  }
  if( pNC->hasAgg ){
    ExprSetProperty(pExpr, EP_Agg);
  }else if( savedHasAgg ){
    pNC->hasAgg = 1;
  }
  return ExprHasProperty(pExpr, EP_Error);
}

/*
** A pointer instance of this structure is used to pass information
** through walkExprTree into codeSubqueryStep().
*/
typedef struct QueryCoder QueryCoder;
struct QueryCoder {
  Parse *pParse;       /* The parsing context */
  NameContext *pNC;    /* Namespace of first enclosing query */
};


/*
** Generate code for scalar subqueries used as an expression
** and IN operators.  Examples:
**
**     (SELECT a FROM b)          -- subquery
**     EXISTS (SELECT a FROM b)   -- EXISTS subquery
**     x IN (4,5,11)              -- IN operator with list on right-hand side
**     x IN (SELECT a FROM b)     -- IN operator with subquery on the right
**
** The pExpr parameter describes the expression that contains the IN
** operator or subquery.
*/
#ifndef SQLITE_OMIT_SUBQUERY
void sqlite3CodeSubselect(Parse *pParse, Expr *pExpr){
  int testAddr = 0;                       /* One-time test address */
  Vdbe *v = sqlite3GetVdbe(pParse);
  if( v==0 ) return;

  /* This code must be run in its entirety every time it is encountered
  ** if any of the following is true:
  **
  **    *  The right-hand side is a correlated subquery
  **    *  The right-hand side is an expression list containing variables
  **    *  We are inside a trigger
  **
  ** If all of the above are false, then we can run this code just once
  ** save the results, and reuse the same result on subsequent invocations.
  */
  if( !ExprHasAnyProperty(pExpr, EP_VarSelect) && !pParse->trigStack ){
    int mem = pParse->nMem++;
    sqlite3VdbeAddOp(v, OP_MemLoad, mem, 0);
    testAddr = sqlite3VdbeAddOp(v, OP_If, 0, 0);
    assert( testAddr>0 || sqlite3MallocFailed() );
    sqlite3VdbeAddOp(v, OP_MemInt, 1, mem);
  }

  switch( pExpr->op ){
    case TK_IN: {
      char affinity;
      KeyInfo keyInfo;
      int addr;        /* Address of OP_OpenEphemeral instruction */

      affinity = sqlite3ExprAffinity(pExpr->pLeft);

      /* Whether this is an 'x IN(SELECT...)' or an 'x IN(<exprlist>)'
      ** expression it is handled the same way. A virtual table is 
      ** filled with single-field index keys representing the results
      ** from the SELECT or the <exprlist>.
      **
      ** If the 'x' expression is a column value, or the SELECT...
      ** statement returns a column value, then the affinity of that
      ** column is used to build the index keys. If both 'x' and the
      ** SELECT... statement are columns, then numeric affinity is used
      ** if either column has NUMERIC or INTEGER affinity. If neither
      ** 'x' nor the SELECT... statement are columns, then numeric affinity
      ** is used.
      */
      pExpr->iTable = pParse->nTab++;
      addr = sqlite3VdbeAddOp(v, OP_OpenEphemeral, pExpr->iTable, 0);
      memset(&keyInfo, 0, sizeof(keyInfo));
      keyInfo.nField = 1;
      sqlite3VdbeAddOp(v, OP_SetNumColumns, pExpr->iTable, 1);

      if( pExpr->pSelect ){
        /* Case 1:     expr IN (SELECT ...)
        **
        ** Generate code to write the results of the select into the temporary
        ** table allocated and opened above.
        */
        int iParm = pExpr->iTable +  (((int)affinity)<<16);
        ExprList *pEList;
        assert( (pExpr->iTable&0x0000FFFF)==pExpr->iTable );
        sqlite3Select(pParse, pExpr->pSelect, SRT_Set, iParm, 0, 0, 0, 0);
        pEList = pExpr->pSelect->pEList;
        if( pEList && pEList->nExpr>0 ){ 
          keyInfo.aColl[0] = binaryCompareCollSeq(pParse, pExpr->pLeft,
              pEList->a[0].pExpr);
        }
      }else if( pExpr->pList ){
        /* Case 2:     expr IN (exprlist)
        **
	** For each expression, build an index key from the evaluation and
        ** store it in the temporary table. If <expr> is a column, then use
        ** that columns affinity when building index keys. If <expr> is not
        ** a column, use numeric affinity.
        */
        int i;
        ExprList *pList = pExpr->pList;
        struct ExprList_item *pItem;

        if( !affinity ){
          affinity = SQLITE_AFF_NONE;
        }
        keyInfo.aColl[0] = pExpr->pLeft->pColl;

        /* Loop through each expression in <exprlist>. */
        for(i=pList->nExpr, pItem=pList->a; i>0; i--, pItem++){
          Expr *pE2 = pItem->pExpr;

          /* If the expression is not constant then we will need to
          ** disable the test that was generated above that makes sure
          ** this code only executes once.  Because for a non-constant
          ** expression we need to rerun this code each time.
          */
          if( testAddr>0 && !sqlite3ExprIsConstant(pE2) ){
            sqlite3VdbeChangeToNoop(v, testAddr-1, 3);
            testAddr = 0;
          }

          /* Evaluate the expression and insert it into the temp table */
          sqlite3ExprCode(pParse, pE2);
          sqlite3VdbeOp3(v, OP_MakeRecord, 1, 0, &affinity, 1);
          sqlite3VdbeAddOp(v, OP_IdxInsert, pExpr->iTable, 0);
        }
      }
      sqlite3VdbeChangeP3(v, addr, (void *)&keyInfo, P3_KEYINFO);
      break;
    }

    case TK_EXISTS:
    case TK_SELECT: {
      /* This has to be a scalar SELECT.  Generate code to put the
      ** value of this select in a memory cell and record the number
      ** of the memory cell in iColumn.
      */
      static const Token one = { (u8*)"1", 0, 1 };
      Select *pSel;
      int iMem;
      int sop;

      pExpr->iColumn = iMem = pParse->nMem++;
      pSel = pExpr->pSelect;
      if( pExpr->op==TK_SELECT ){
        sop = SRT_Mem;
        sqlite3VdbeAddOp(v, OP_MemNull, iMem, 0);
        VdbeComment((v, "# Init subquery result"));
      }else{
        sop = SRT_Exists;
        sqlite3VdbeAddOp(v, OP_MemInt, 0, iMem);
        VdbeComment((v, "# Init EXISTS result"));
      }
      sqlite3ExprDelete(pSel->pLimit);
      pSel->pLimit = sqlite3Expr(TK_INTEGER, 0, 0, &one);
      sqlite3Select(pParse, pSel, sop, iMem, 0, 0, 0, 0);
      break;
    }
  }

  if( testAddr ){
    sqlite3VdbeJumpHere(v, testAddr);
  }
  return;
}
#endif /* SQLITE_OMIT_SUBQUERY */

/*
** Generate an instruction that will put the integer describe by
** text z[0..n-1] on the stack.
*/
static void codeInteger(Vdbe *v, const char *z, int n){
  int i;
  if( sqlite3GetInt32(z, &i) ){
    sqlite3VdbeAddOp(v, OP_Integer, i, 0);
  }else if( sqlite3FitsIn64Bits(z) ){
    sqlite3VdbeOp3(v, OP_Int64, 0, 0, z, n);
  }else{
    sqlite3VdbeOp3(v, OP_Real, 0, 0, z, n);
  }
}

/*
** Generate code into the current Vdbe to evaluate the given
** expression and leave the result on the top of stack.
**
** This code depends on the fact that certain token values (ex: TK_EQ)
** are the same as opcode values (ex: OP_Eq) that implement the corresponding
** operation.  Special comments in vdbe.c and the mkopcodeh.awk script in
** the make process cause these values to align.  Assert()s in the code
** below verify that the numbers are aligned correctly.
*/
void sqlite3ExprCode(Parse *pParse, Expr *pExpr){
  Vdbe *v = pParse->pVdbe;
  int op;
  int stackChng = 1;    /* Amount of change to stack depth */

  if( v==0 ) return;
  if( pExpr==0 ){
    sqlite3VdbeAddOp(v, OP_Null, 0, 0);
    return;
  }
  op = pExpr->op;
  switch( op ){
    case TK_AGG_COLUMN: {
      AggInfo *pAggInfo = pExpr->pAggInfo;
      struct AggInfo_col *pCol = &pAggInfo->aCol[pExpr->iAgg];
      if( !pAggInfo->directMode ){
        sqlite3VdbeAddOp(v, OP_MemLoad, pCol->iMem, 0);
        break;
      }else if( pAggInfo->useSortingIdx ){
        sqlite3VdbeAddOp(v, OP_Column, pAggInfo->sortingIdx,
                              pCol->iSorterColumn);
        break;
      }
      /* Otherwise, fall thru into the TK_COLUMN case */
    }
    case TK_COLUMN: {
      if( pExpr->iTable<0 ){
        /* This only happens when coding check constraints */
        assert( pParse->ckOffset>0 );
        sqlite3VdbeAddOp(v, OP_Dup, pParse->ckOffset-pExpr->iColumn-1, 1);
      }else if( pExpr->iColumn>=0 ){
        Table *pTab = pExpr->pTab;
        int iCol = pExpr->iColumn;
        int op = (pTab && IsVirtual(pTab)) ? OP_VColumn : OP_Column;
        sqlite3VdbeAddOp(v, op, pExpr->iTable, iCol);
        sqlite3ColumnDefault(v, pTab, iCol);
#ifndef SQLITE_OMIT_FLOATING_POINT
        if( pTab && pTab->aCol[iCol].affinity==SQLITE_AFF_REAL ){
          sqlite3VdbeAddOp(v, OP_RealAffinity, 0, 0);
        }
#endif
      }else{
        Table *pTab = pExpr->pTab;
        int op = (pTab && IsVirtual(pTab)) ? OP_VRowid : OP_Rowid;
        sqlite3VdbeAddOp(v, op, pExpr->iTable, 0);
      }
      break;
    }
    case TK_INTEGER: {
      codeInteger(v, (char*)pExpr->token.z, pExpr->token.n);
      break;
    }
    case TK_FLOAT:
    case TK_STRING: {
      assert( TK_FLOAT==OP_Real );
      assert( TK_STRING==OP_String8 );
      sqlite3DequoteExpr(pExpr);
      sqlite3VdbeOp3(v, op, 0, 0, (char*)pExpr->token.z, pExpr->token.n);
      break;
    }
    case TK_NULL: {
      sqlite3VdbeAddOp(v, OP_Null, 0, 0);
      break;
    }
#ifndef SQLITE_OMIT_BLOB_LITERAL
    case TK_BLOB: {
      int n;
      const char *z;
      assert( TK_BLOB==OP_HexBlob );
      n = pExpr->token.n - 3;
      z = (char*)pExpr->token.z + 2;
      assert( n>=0 );
      if( n==0 ){
        z = "";
      }
      sqlite3VdbeOp3(v, op, 0, 0, z, n);
      break;
    }
#endif
    case TK_VARIABLE: {
      sqlite3VdbeAddOp(v, OP_Variable, pExpr->iTable, 0);
      if( pExpr->token.n>1 ){
        sqlite3VdbeChangeP3(v, -1, (char*)pExpr->token.z, pExpr->token.n);
      }
      break;
    }
    case TK_REGISTER: {
      sqlite3VdbeAddOp(v, OP_MemLoad, pExpr->iTable, 0);
      break;
    }
#ifndef SQLITE_OMIT_CAST
    case TK_CAST: {
      /* Expressions of the form:   CAST(pLeft AS token) */
      int aff, to_op;
      sqlite3ExprCode(pParse, pExpr->pLeft);
      aff = sqlite3AffinityType(&pExpr->token);
      to_op = aff - SQLITE_AFF_TEXT + OP_ToText;
      assert( to_op==OP_ToText    || aff!=SQLITE_AFF_TEXT    );
      assert( to_op==OP_ToBlob    || aff!=SQLITE_AFF_NONE    );
      assert( to_op==OP_ToNumeric || aff!=SQLITE_AFF_NUMERIC );
      assert( to_op==OP_ToInt     || aff!=SQLITE_AFF_INTEGER );
      assert( to_op==OP_ToReal    || aff!=SQLITE_AFF_REAL    );
      sqlite3VdbeAddOp(v, to_op, 0, 0);
      stackChng = 0;
      break;
    }
#endif /* SQLITE_OMIT_CAST */
    case TK_LT:
    case TK_LE:
    case TK_GT:
    case TK_GE:
    case TK_NE:
    case TK_EQ: {
      assert( TK_LT==OP_Lt );
      assert( TK_LE==OP_Le );
      assert( TK_GT==OP_Gt );
      assert( TK_GE==OP_Ge );
      assert( TK_EQ==OP_Eq );
      assert( TK_NE==OP_Ne );
      sqlite3ExprCode(pParse, pExpr->pLeft);
      sqlite3ExprCode(pParse, pExpr->pRight);
      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op, 0, 0);
      stackChng = -1;
      break;
    }
    case TK_AND:
    case TK_OR:
    case TK_PLUS:
    case TK_STAR:
    case TK_MINUS:
    case TK_REM:
    case TK_BITAND:
    case TK_BITOR:
    case TK_SLASH:
    case TK_LSHIFT:
    case TK_RSHIFT: 
    case TK_CONCAT: {
      assert( TK_AND==OP_And );
      assert( TK_OR==OP_Or );
      assert( TK_PLUS==OP_Add );
      assert( TK_MINUS==OP_Subtract );
      assert( TK_REM==OP_Remainder );
      assert( TK_BITAND==OP_BitAnd );
      assert( TK_BITOR==OP_BitOr );
      assert( TK_SLASH==OP_Divide );
      assert( TK_LSHIFT==OP_ShiftLeft );