SQLite

**    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 1.517 2009/05/18 15:46:08 drh Exp $
*/
#include "sqliteInt.h"


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

*/
static u8 minMaxQuery(Select *p){
  Expr *pExpr;
  ExprList *pEList = p->pEList;

  if( pEList->nExpr!=1 ) return WHERE_ORDERBY_NORMAL;
  pExpr = pEList->a[0].pExpr;

  if( ExprHasProperty(pExpr, EP_xIsSelect) ) return 0;
  pEList = pExpr->x.pList;
  if( pExpr->op!=TK_AGG_FUNCTION || pEList==0 || pEList->nExpr!=1 ) return 0;
  if( pEList->a[0].pExpr->op!=TK_AGG_COLUMN ) return WHERE_ORDERBY_NORMAL;
  if( pExpr->token.n!=3 ) return WHERE_ORDERBY_NORMAL;
  if( sqlite3StrNICmp((char*)pExpr->token.z,"min",3)==0 ){
    return WHERE_ORDERBY_MIN;
  }else if( sqlite3StrNICmp((char*)pExpr->token.z,"max",3)==0 ){
    return WHERE_ORDERBY_MAX;
  }

  ExprList *pEList;
  struct SrcList_item *pFrom;
  sqlite3 *db = pParse->db;

  if( db->mallocFailed  ){
    return WRC_Abort;
  }
  if( p->pSrc==0 || (p->selFlags & SF_Expanded)!=0 ){
    return WRC_Prune;
  }
  p->selFlags |= SF_Expanded;
  pTabList = p->pSrc;
  pEList = p->pEList;

  /* Make sure cursor numbers have been assigned to all entries in

        sqlite3LocateTable(pParse,0,pFrom->zName,pFrom->zDatabase);
      if( pTab==0 ) return WRC_Abort;
      pTab->nRef++;
#if !defined(SQLITE_OMIT_VIEW) || !defined (SQLITE_OMIT_VIRTUALTABLE)
      if( pTab->pSelect || IsVirtual(pTab) ){
        /* We reach here if the named table is a really a view */
        if( sqlite3ViewGetColumnNames(pParse, pTab) ) return WRC_Abort;

        /* If pFrom->pSelect!=0 it means we are dealing with a
        ** view within a view.  The SELECT structure has already been
        ** copied by the outer view so we can skip the copy step here
        ** in the inner view.
        */
        if( pFrom->pSelect==0 ){
          pFrom->pSelect = sqlite3SelectDup(db, pTab->pSelect, 0);
          sqlite3WalkSelect(pWalker, pFrom->pSelect);
        }
      }
#endif
    }

    /* Locate the index named by the INDEXED BY clause, if any. */
    if( sqlite3IndexedByLookup(pParse, pFrom) ){
      return WRC_Abort;

  **
  ** The first loop just checks to see if there are any "*" operators
  ** that need expanding.
  */
  for(k=0; k<pEList->nExpr; k++){
    Expr *pE = pEList->a[k].pExpr;
    if( pE->op==TK_ALL ) break;


    if( pE->op==TK_DOT && pE->pRight && pE->pRight->op==TK_ALL
         && pE->pLeft && pE->pLeft->op==TK_ID ) break;
  }
  if( k<pEList->nExpr ){
    /*
    ** If we get here it means the result set contains one or more "*"
    ** operators that need to be expanded.  Loop through each expression
    ** in the result set and expand them one by one.
    */
    struct ExprList_item *a = pEList->a;
    ExprList *pNew = 0;
    int flags = pParse->db->flags;
    int longNames = (flags & SQLITE_FullColNames)!=0
                      && (flags & SQLITE_ShortColNames)==0;

    for(k=0; k<pEList->nExpr; k++){
      Expr *pE = a[k].pExpr;
      if( pE->op!=TK_ALL &&
           (pE->op!=TK_DOT || pE->pRight==0 || pE->pRight->op!=TK_ALL) ){
        /* This particular expression does not need to be expanded.
        */
        pNew = sqlite3ExprListAppend(pParse, pNew, a[k].pExpr, 0);
        if( pNew ){
          pNew->a[pNew->nExpr-1].zName = a[k].zName;
        }
        a[k].pExpr = 0;
        a[k].zName = 0;
      }else{
        /* This expression is a "*" or a "TABLE.*" and needs to be
        ** expanded. */
        int tableSeen = 0;      /* Set to 1 when TABLE matches */
        char *zTName;            /* text of name of TABLE */
        if( pE->op==TK_DOT && pE->pLeft ){

          zTName = sqlite3NameFromToken(db, &pE->pLeft->token);
        }else{
          zTName = 0;
        }
        for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
          Table *pTab = pFrom->pTab;
          char *zTabName = pFrom->zAlias;
          if( zTabName==0 || zTabName[0]==0 ){ 
            zTabName = pTab->zName;
          }
          if( db->mallocFailed ) break;
          if( zTName && sqlite3StrICmp(zTName, zTabName)!=0 ){
            continue;
          }
          tableSeen = 1;

static int selectAddSubqueryTypeInfo(Walker *pWalker, Select *p){
  Parse *pParse;
  int i;
  SrcList *pTabList;
  struct SrcList_item *pFrom;

  assert( p->selFlags & SF_Resolved );
  if( (p->selFlags & SF_HasTypeInfo)==0 ){
    p->selFlags |= SF_HasTypeInfo;
    pParse = pWalker->pParse;
    pTabList = p->pSrc;
    for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
      Table *pTab = pFrom->pTab;
      if( pTab && (pTab->tabFlags & TF_Ephemeral)!=0 ){
        /* A sub-query in the FROM clause of a SELECT */
        Select *pSel = pFrom->pSelect;
        assert( pSel );
        while( pSel->pPrior ) pSel = pSel->pPrior;
        selectAddColumnTypeAndCollation(pParse, pTab->nCol, pTab->aCol, pSel);
      }
    }
  }
  return WRC_Continue;
}
#endif

*/
void sqlite3SelectPrep(
  Parse *pParse,         /* The parser context */
  Select *p,             /* The SELECT statement being coded. */
  NameContext *pOuterNC  /* Name context for container */
){
  sqlite3 *db;
  if( p==0 ) return;
  db = pParse->db;
  if( p->selFlags & SF_HasTypeInfo ) return;
  if( pParse->nErr || db->mallocFailed ) return;
  sqlite3SelectExpand(pParse, p);
  if( pParse->nErr || db->mallocFailed ) return;
  sqlite3ResolveSelectNames(pParse, p, pOuterNC);
  if( pParse->nErr || db->mallocFailed ) return;
  sqlite3SelectAddTypeInfo(pParse, p);
}

  pOrderBy = p->pOrderBy;
  pTabList = p->pSrc;
  pEList = p->pEList;
  if( pParse->nErr || db->mallocFailed ){
    goto select_end;
  }
  isAgg = (p->selFlags & SF_Aggregate)!=0;
  if( pEList==0 ) goto select_end;

  /* 
  ** Do not even attempt to generate any code if we have already seen
  ** errors before this routine starts.
  */
  if( pParse->nErr>0 ) goto select_end;

  /* Begin generating code.
  */
  v = sqlite3GetVdbe(pParse);
  if( v==0 ) goto select_end;

  /* Generate code for all sub-queries in the FROM clause

      i = -1;
    }else{
      sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
      assert( pItem->isPopulated==0 );
      sqlite3Select(pParse, pSub, &dest);
      pItem->isPopulated = 1;
    }
    if( pParse->nErr || db->mallocFailed ){
      goto select_end;
    }
    pParse->nHeight -= sqlite3SelectExprHeight(p);
    pTabList = p->pSrc;
    if( !IgnorableOrderby(pDest) ){
      pOrderBy = p->pOrderBy;
    }

    goto select_end;
  }
#endif

  /* If possible, rewrite the query to use GROUP BY instead of DISTINCT.
  ** GROUP BY might use an index, DISTINCT never does.
  */

  if( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct && !p->pGroupBy ){
    p->pGroupBy = sqlite3ExprListDup(db, p->pEList, 0);
    pGroupBy = p->pGroupBy;
    p->selFlags &= ~SF_Distinct;
    isDistinct = 0;
  }

  /* If there is an ORDER BY clause, then this sorting

      /* Generate a subroutine that will reset the group-by accumulator
      */
      sqlite3VdbeResolveLabel(v, addrReset);
      resetAccumulator(pParse, &sAggInfo);
      sqlite3VdbeAddOp1(v, OP_Return, regReset);
     
    } /* endif pGroupBy */
    else {
      ExprList *pDel = 0;
#ifndef SQLITE_OMIT_BTREECOUNT
      Table *pTab;
      if( (pTab = isSimpleCount(p, &sAggInfo))!=0 ){
        /* If isSimpleCount() returns a pointer to a Table structure, then
        ** the SQL statement is of the form: