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 1.348 2008/01/17 17:15:56 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Return the 'affinity' of the expression pExpr if any.
**

      pDef = sqlite3FindFunction(pParse->db, zId, nId, nExpr, enc, 0);
      assert( pDef!=0 );
      if( pList ){
        nExpr = pList->nExpr;
        r1 = sqlite3GetTempRange(pParse, nExpr);
        sqlite3ExprCodeExprList(pParse, pList, r1);
      }else{
        nExpr = r1 = 0;
      }
#ifndef SQLITE_OMIT_VIRTUALTABLE
      /* Possibly overload the function if the first argument is
      ** a virtual table column.
      **
      ** For infix functions (LIKE, GLOB, REGEXP, and MATCH) use the
      ** second argument, not the first, as the argument to test to

**    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 1.405 2008/01/17 17:15:56 drh Exp $
*/
#include "sqliteInt.h"


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

  int distinct,           /* If >=0, make sure results are distinct */
  SelectDest *pDest,      /* How to dispose of the results */
  int iContinue,          /* Jump here to continue with next row */
  int iBreak,             /* Jump here to break out of the inner loop */
  char *aff               /* affinity string if eDest is SRT_Union */
){
  Vdbe *v = pParse->pVdbe;
  int i;
  int hasDistinct;        /* True if the DISTINCT keyword is present */
  int regResult;              /* Start of memory holding result set */
  int eDest = pDest->eDest;   /* How to dispose of results */
  int iParm = pDest->iParm;   /* First argument to disposal method */
  int nResultCol;             /* Number of result columns */
  int nToFree;                /* Number of result columns to release */

  if( v==0 ) return 0;
  assert( pEList!=0 );

  /* If there was a LIMIT clause on the SELECT statement, then do the check
  ** to see if this row should be output.
  */
  hasDistinct = distinct>=0 && pEList->nExpr>0;
  if( pOrderBy==0 && !hasDistinct ){
    codeOffset(v, p, iContinue);
  }

  /* Pull the requested columns.
  */
  if( nColumn>0 ){
    nResultCol = nColumn;
  }else{
    nResultCol = pEList->nExpr;
  }
  if( pDest->iMem>0 ){
    regResult = pDest->iMem;
    nToFree = 0;
  }else{
    pDest->iMem = regResult = sqlite3GetTempRange(pParse, nResultCol);
    nToFree = nResultCol;
  }
  if( nColumn>0 ){
    for(i=0; i<nColumn; i++){
      sqlite3VdbeAddOp3(v, OP_Column, srcTab, i, regResult+i);
    }
  }else if( eDest!=SRT_Exists ){
    /* If the destination is an EXISTS(...) expression, the actual
    ** values returned by the SELECT are not required.
    */
    for(i=0; i<nResultCol; i++){
      sqlite3ExprCode(pParse, pEList->a[i].pExpr, regResult+i);
    }
  }
  nColumn = nResultCol;

  /* If the DISTINCT keyword was present on the SELECT statement
  ** and this row has been seen before, then do not make this row
  ** part of the result.
  */
  if( hasDistinct ){
    assert( pEList!=0 );
    assert( pEList->nExpr==nColumn );
    codeDistinct(pParse, distinct, iContinue, nColumn, regResult);
    if( pOrderBy==0 ){
      codeOffset(v, p, iContinue);
    }
  }

  if( checkForMultiColumnSelectError(pParse, pDest, pEList->nExpr) ){
    return 0;
  }

  switch( eDest ){
    /* In this mode, write each query result to the key of the temporary
    ** table iParm.
    */
#ifndef SQLITE_OMIT_COMPOUND_SELECT
    case SRT_Union: {
      int r1;
      r1 = sqlite3GetTempReg(pParse);
      sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
      if( aff ){
        sqlite3VdbeChangeP4(v, -1, aff, P4_STATIC);
      }
      sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, r1);
      sqlite3ReleaseTempReg(pParse, r1);
      break;
    }

    /* Construct a record from the query result, but instead of
    ** saving that record, use it as a key to delete elements from
    ** the temporary table iParm.
    */
    case SRT_Except: {
      int addr, r1;
      r1 = sqlite3GetTempReg(pParse);
      addr = sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
      sqlite3VdbeChangeP4(v, -1, aff, P4_STATIC);
      sqlite3VdbeAddOp3(v, OP_NotFound, iParm, addr+3, r1);
      sqlite3VdbeAddOp1(v, OP_Delete, iParm);
      sqlite3ReleaseTempReg(pParse, r1);
      break;
    }
#endif

    /* Store the result as data using a unique key.
    */
    case SRT_Table:
    case SRT_EphemTab: {
      int r1 = sqlite3GetTempReg(pParse);
      sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
      if( pOrderBy ){
        pushOntoSorter(pParse, pOrderBy, p, r1);
      }else{
        int r2 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, r2);
        sqlite3VdbeAddOp3(v, OP_Insert, iParm, r1, r2);
        sqlite3VdbeChangeP5(v, OPFLAG_APPEND);

    ** then there should be a single item on the stack.  Write this
    ** item into the set table with bogus data.
    */
    case SRT_Set: {
      int addr2;

      assert( nColumn==1 );
      addr2 = sqlite3VdbeAddOp1(v, OP_IsNull, regResult);
      p->affinity = sqlite3CompareAffinity(pEList->a[0].pExpr, pDest->affinity);
      if( pOrderBy ){
        /* At first glance you would think we could optimize out the
        ** ORDER BY in this case since the order of entries in the set
        ** does not matter.  But there might be a LIMIT clause, in which
        ** case the order does matter */
        pushOntoSorter(pParse, pOrderBy, p, regResult);
      }else{
        int r1 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp4(v, OP_MakeRecord, regResult, 1, r1, &p->affinity, 1);
        sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, r1);
        sqlite3ReleaseTempReg(pParse, r1);
      }
      sqlite3VdbeJumpHere(v, addr2);
      break;
    }

    /* If this is a scalar select that is part of an expression, then
    ** store the results in the appropriate memory cell and break out
    ** of the scan loop.
    */
    case SRT_Mem: {
      assert( nColumn==1 );
      if( pOrderBy ){
        pushOntoSorter(pParse, pOrderBy, p, regResult);
      }else{
        sqlite3VdbeAddOp2(v, OP_Move, regResult, iParm);
        /* The LIMIT clause will jump out of the loop for us */
      }
      break;
    }
#endif /* #ifndef SQLITE_OMIT_SUBQUERY */

    /* Send the data to the callback function or to a subroutine.  In the
    ** case of a subroutine, the subroutine itself is responsible for
    ** popping the data from the stack.
    */
    case SRT_Subroutine:
    case SRT_Callback: {
      if( pOrderBy ){
        int r1 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
        pushOntoSorter(pParse, pOrderBy, p, r1);
        sqlite3ReleaseTempReg(pParse, r1);
      }else if( eDest==SRT_Subroutine ){
        nToFree = 0;  /* Preserve registers. Subroutine will need them. */
        sqlite3VdbeAddOp2(v, OP_Gosub, 0, iParm);
      }else{
        sqlite3VdbeAddOp2(v, OP_ResultRow, regResult, nColumn);
      }
      break;
    }

#if !defined(SQLITE_OMIT_TRIGGER)
    /* Discard the results.  This is used for SELECT statements inside
    ** the body of a TRIGGER.  The purpose of such selects is to call

  /* Jump to the end of the loop if the LIMIT is reached.
  */
  if( p->iLimit>=0 && pOrderBy==0 ){
    sqlite3VdbeAddOp2(v, OP_AddImm, p->iLimit, -1);
    sqlite3VdbeAddOp2(v, OP_IfZero, p->iLimit, iBreak);
  }
  sqlite3ReleaseTempRange(pParse, regResult, nToFree);
  return 0;
}

/*
** Given an expression list, generate a KeyInfo structure that records
** the collating sequence for each expression in that expression list.
**