SQLite

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.443 2009/05/30 20:49:20 drh Exp $
*/
#include "sqliteInt.h"

/*
** Return the 'affinity' of the expression pExpr if any.
**
** If pExpr is a column, a reference to a column via an 'AS' alias,

    ** exprssion is NULL.
    ** Ei is in pExpr->pList->a[i*2] and Ri is pExpr->pList->a[i*2+1].
    **
    ** The result of the expression is the Ri for the first matching Ei,
    ** or if there is no matching Ei, the ELSE term Y, or if there is
    ** no ELSE term, NULL.
    */
    default: assert( op==TK_CASE ); {
      int endLabel;                     /* GOTO label for end of CASE stmt */
      int nextCase;                     /* GOTO label for next WHEN clause */
      int nExpr;                        /* 2x number of WHEN terms */
      int i;                            /* Loop counter */
      ExprList *pEList;                 /* List of WHEN terms */
      struct ExprList_item *aListelem;  /* Array of WHEN terms */
      Expr opCompare;                   /* The X==Ei expression */

      assert(pExpr->x.pList->nExpr > 0);
      pEList = pExpr->x.pList;
      aListelem = pEList->a;
      nExpr = pEList->nExpr;
      endLabel = sqlite3VdbeMakeLabel(v);
      if( (pX = pExpr->pLeft)!=0 ){
        cacheX = *pX;
        testcase( pX->op==TK_COLUMN );
        testcase( pX->op==TK_REGISTER );
        cacheX.iTable = sqlite3ExprCodeTemp(pParse, pX, &regFree1);
        testcase( regFree1==0 );
        cacheX.op = TK_REGISTER;
        opCompare.op = TK_EQ;
        opCompare.pLeft = &cacheX;
        pTest = &opCompare;
      }
      for(i=0; i<nExpr; i=i+2){
        sqlite3ExprCachePush(pParse);
        if( pX ){
          assert( pTest!=0 );
          opCompare.pRight = aListelem[i].pExpr;
        }else{
          pTest = aListelem[i].pExpr;
        }
        nextCase = sqlite3VdbeMakeLabel(v);
        testcase( pTest->op==TK_COLUMN );
        testcase( pTest->op==TK_COLUMN );
        sqlite3ExprIfFalse(pParse, pTest, nextCase, SQLITE_JUMPIFNULL);
        testcase( aListelem[i+1].pExpr->op==TK_COLUMN );
        testcase( aListelem[i+1].pExpr->op==TK_REGISTER );
        sqlite3ExprCode(pParse, aListelem[i+1].pExpr, target);
        sqlite3VdbeAddOp2(v, OP_Goto, 0, endLabel);
        sqlite3ExprCachePop(pParse, 1);
        sqlite3VdbeResolveLabel(v, nextCase);

** into a register and convert the expression into a TK_REGISTER
** expression.
*/
static int evalConstExpr(Walker *pWalker, Expr *pExpr){
  Parse *pParse = pWalker->pParse;
  switch( pExpr->op ){
    case TK_REGISTER: {
      return WRC_Prune;
    }
    case TK_FUNCTION:
    case TK_AGG_FUNCTION:
    case TK_CONST_FUNC: {
      /* The arguments to a function have a fixed destination.
      ** Mark them this way to avoid generated unneeded OP_SCopy
      ** instructions. 
      */
      ExprList *pList = pExpr->x.pList;
      assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
      if( pList ){
        int i = pList->nExpr;
        struct ExprList_item *pItem = pList->a;
        for(; i>0; i--, pItem++){
          if( ALWAYS(pItem->pExpr) ) pItem->pExpr->flags |= EP_FixedDest;
        }
      }
      break;
    }
  }
  if( isAppropriateForFactoring(pExpr) ){
    int r1 = ++pParse->nMem;
    int r2;
    r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);
    if( NEVER(r1!=r2) ) sqlite3ReleaseTempReg(pParse, r1);
    pExpr->op = TK_REGISTER;
    pExpr->iTable = r2;
    return WRC_Prune;
  }
  return WRC_Continue;
}

  Vdbe *v = pParse->pVdbe;
  int op = 0;
  int regFree1 = 0;
  int regFree2 = 0;
  int r1, r2;

  assert( jumpIfNull==SQLITE_JUMPIFNULL || jumpIfNull==0 );
  if( NEVER(v==0) )     return;  /* Existance of VDBE checked by caller */
  if( NEVER(pExpr==0) ) return;  /* No way this can happen */
  op = pExpr->op;
  switch( op ){
    case TK_AND: {
      int d2 = sqlite3VdbeMakeLabel(v);
      testcase( jumpIfNull==0 );
      sqlite3ExprCachePush(pParse);
      sqlite3ExprIfFalse(pParse, pExpr->pLeft, d2,jumpIfNull^SQLITE_JUMPIFNULL);

  Vdbe *v = pParse->pVdbe;
  int op = 0;
  int regFree1 = 0;
  int regFree2 = 0;
  int r1, r2;

  assert( jumpIfNull==SQLITE_JUMPIFNULL || jumpIfNull==0 );
  if( NEVER(v==0) ) return; /* Existance of VDBE checked by caller */
  if( pExpr==0 )    return;

  /* The value of pExpr->op and op are related as follows:
  **
  **       pExpr->op            op
  **       ---------          ----------
  **       TK_ISNULL          OP_NotNull
  **       TK_NOTNULL         OP_IsNull

**    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
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.521 2009/05/30 20:49:20 drh Exp $
*/
#include "sqliteInt.h"


/*
** Delete all the content of a Select structure but do not deallocate
** the select structure itself.

      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
      sqlite3VdbeResolveLabel(v, addrOutputRow);
      addrOutputRow = sqlite3VdbeCurrentAddr(v);
      sqlite3VdbeAddOp2(v, OP_IfPos, iUseFlag, addrOutputRow+2);
      VdbeComment((v, "Groupby result generator entry point"));
      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
      finalizeAggFunctions(pParse, &sAggInfo);

      sqlite3ExprIfFalse(pParse, pHaving, addrOutputRow+1, SQLITE_JUMPIFNULL);

      selectInnerLoop(pParse, p, p->pEList, 0, 0, pOrderBy,
                      distinct, pDest,
                      addrOutputRow+1, addrSetAbort);
      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
      VdbeComment((v, "end groupby result generator"));

      /* Generate a subroutine that will reset the group-by accumulator

                (flag==WHERE_ORDERBY_MIN?"min":"max")));
        }
        sqlite3WhereEnd(pWInfo);
        finalizeAggFunctions(pParse, &sAggInfo);
      }

      pOrderBy = 0;

      sqlite3ExprIfFalse(pParse, pHaving, addrEnd, SQLITE_JUMPIFNULL);

      selectInnerLoop(pParse, p, p->pEList, 0, 0, 0, -1, 
                      pDest, addrEnd, addrEnd);
      sqlite3ExprListDelete(db, pDel);
    }
    sqlite3VdbeResolveLabel(v, addrEnd);
    
  } /* endif aggregate query */