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Overview
Comment:Simplify the interface to the subst() routines that are part of the query flattener by collecting common parameters into the SubstContext object and passing around a pointer to that object.
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SHA3-256: e651074be28b2077b8a298f513e2e699ceca99164ace9869ea50873c0637fd2e
User & Date: drh 2017-04-14 12:39:37
Context
2017-04-14
14:02
Enhance the sqlite3TreeView() display for Expr objects so that it shows the iRightJoinTable value for Expr nodes that have the EP_FromJoin property. check-in: 5159cb8f user: drh tags: trunk
12:39
Simplify the interface to the subst() routines that are part of the query flattener by collecting common parameters into the SubstContext object and passing around a pointer to that object. check-in: e651074b user: drh tags: trunk
12:27
Remove an incorrect ALWAYS(). check-in: f956f6ae user: drh tags: trunk
Changes
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Changes to src/select.c.

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  **** subqueries ****/
  explainComposite(pParse, p->op, iSub1, iSub2, 0);
  return pParse->nErr!=0;
}
#endif

#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)













/* Forward Declarations */
static void substExprList(Parse*, ExprList*, int, ExprList*);
static void substSelect(Parse*, Select *, int, ExprList*, int);

/*
** Scan through the expression pExpr.  Replace every reference to
** a column in table number iTable with a copy of the iColumn-th
** entry in pEList.  (But leave references to the ROWID column 
** unchanged.)
**
................................................................................
** whose result set is defined by pEList appears as entry in the
** FROM clause of a SELECT such that the VDBE cursor assigned to that
** FORM clause entry is iTable.  This routine makes the necessary 
** changes to pExpr so that it refers directly to the source table
** of the subquery rather the result set of the subquery.
*/
static Expr *substExpr(
  Parse *pParse,      /* Report errors here */
  Expr *pExpr,        /* Expr in which substitution occurs */
  int iTable,         /* Table to be substituted */
  ExprList *pEList    /* Substitute expressions */
){
  sqlite3 *db = pParse->db;
  if( pExpr==0 ) return 0;
  if( pExpr->op==TK_COLUMN && pExpr->iTable==iTable ){
    if( pExpr->iColumn<0 ){
      pExpr->op = TK_NULL;
    }else{
      Expr *pNew;
      Expr *pCopy = pEList->a[pExpr->iColumn].pExpr;
      assert( pEList!=0 && pExpr->iColumn<pEList->nExpr );
      assert( pExpr->pLeft==0 && pExpr->pRight==0 );
      if( sqlite3ExprIsVector(pCopy) ){
        sqlite3VectorErrorMsg(pParse, pCopy);
      }else{

        pNew = sqlite3ExprDup(db, pCopy, 0);
        if( pNew && (pExpr->flags & EP_FromJoin) ){
          pNew->iRightJoinTable = pExpr->iRightJoinTable;
          pNew->flags |= EP_FromJoin;
        }
        sqlite3ExprDelete(db, pExpr);
        pExpr = pNew;
      }
    }
  }else{
    pExpr->pLeft = substExpr(pParse, pExpr->pLeft, iTable, pEList);
    pExpr->pRight = substExpr(pParse, pExpr->pRight, iTable, pEList);
    if( ExprHasProperty(pExpr, EP_xIsSelect) ){
      substSelect(pParse, pExpr->x.pSelect, iTable, pEList, 1);
    }else{
      substExprList(pParse, pExpr->x.pList, iTable, pEList);
    }
  }
  return pExpr;
}
static void substExprList(
  Parse *pParse,       /* Report errors here */
  ExprList *pList,     /* List to scan and in which to make substitutes */
  int iTable,          /* Table to be substituted */
  ExprList *pEList     /* Substitute values */
){
  int i;
  if( pList==0 ) return;
  for(i=0; i<pList->nExpr; i++){
    pList->a[i].pExpr = substExpr(pParse, pList->a[i].pExpr, iTable, pEList);
  }
}
static void substSelect(
  Parse *pParse,       /* Report errors here */
  Select *p,           /* SELECT statement in which to make substitutions */
  int iTable,          /* Table to be replaced */
  ExprList *pEList,    /* Substitute values */
  int doPrior          /* Do substitutes on p->pPrior too */
){
  SrcList *pSrc;
  struct SrcList_item *pItem;
  int i;
  if( !p ) return;
  do{
    substExprList(pParse, p->pEList, iTable, pEList);
    substExprList(pParse, p->pGroupBy, iTable, pEList);
    substExprList(pParse, p->pOrderBy, iTable, pEList);
    p->pHaving = substExpr(pParse, p->pHaving, iTable, pEList);
    p->pWhere = substExpr(pParse, p->pWhere, iTable, pEList);
    pSrc = p->pSrc;
    assert( pSrc!=0 );
    for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
      substSelect(pParse, pItem->pSelect, iTable, pEList, 1);
      if( pItem->fg.isTabFunc ){
        substExprList(pParse, pItem->u1.pFuncArg, iTable, pEList);
      }
    }
  }while( doPrior && (p = p->pPrior)!=0 );
}
#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */

#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
................................................................................
      );
      assert( pParent->pGroupBy==0 );
      pParent->pGroupBy = sqlite3ExprListDup(db, pSub->pGroupBy, 0);
    }else{
      pParent->pWhere = sqlite3ExprAnd(db, pWhere, pParent->pWhere);
    }
    if( db->mallocFailed==0 ){
      substSelect(pParse, pParent, iParent, pSub->pEList, 0);




    }
  
    /* The flattened query is distinct if either the inner or the
    ** outer query is distinct. 
    */
    pParent->selFlags |= pSub->selFlags & SF_Distinct;
  
................................................................................
    nChng += pushDownWhereTerms(pParse, pSubq, pWhere->pRight, iCursor);
    pWhere = pWhere->pLeft;
  }
  if( ExprHasProperty(pWhere,EP_FromJoin) ) return 0; /* restriction 5 */
  if( sqlite3ExprIsTableConstant(pWhere, iCursor) ){
    nChng++;
    while( pSubq ){

      pNew = sqlite3ExprDup(pParse->db, pWhere, 0);



      pNew = substExpr(pParse, pNew, iCursor, pSubq->pEList);
      pSubq->pWhere = sqlite3ExprAnd(pParse->db, pSubq->pWhere, pNew);
      pSubq = pSubq->pPrior;
    }
  }
  return nChng;
}
#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */







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  **** subqueries ****/
  explainComposite(pParse, p->op, iSub1, iSub2, 0);
  return pParse->nErr!=0;
}
#endif

#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)

/* An instance of the SubstContext object describes an substitution edit
** to be performed on a parse tree.
**
** All references to columns in table iTable are to be replaced by corresponding
** expressions in pEList.
*/
typedef struct SubstContext {
  Parse *pParse;            /* The parsing context */
  int iTable;               /* Replace references to this table */
  ExprList *pEList;         /* Replacement expressions */
} SubstContext;

/* Forward Declarations */
static void substExprList(SubstContext*, ExprList*);
static void substSelect(SubstContext*, Select*, int);

/*
** Scan through the expression pExpr.  Replace every reference to
** a column in table number iTable with a copy of the iColumn-th
** entry in pEList.  (But leave references to the ROWID column 
** unchanged.)
**
................................................................................
** whose result set is defined by pEList appears as entry in the
** FROM clause of a SELECT such that the VDBE cursor assigned to that
** FORM clause entry is iTable.  This routine makes the necessary 
** changes to pExpr so that it refers directly to the source table
** of the subquery rather the result set of the subquery.
*/
static Expr *substExpr(
  SubstContext *pSubst,  /* Description of the substitution */
  Expr *pExpr            /* Expr in which substitution occurs */


){

  if( pExpr==0 ) return 0;
  if( pExpr->op==TK_COLUMN && pExpr->iTable==pSubst->iTable ){
    if( pExpr->iColumn<0 ){
      pExpr->op = TK_NULL;
    }else{
      Expr *pNew;
      Expr *pCopy = pSubst->pEList->a[pExpr->iColumn].pExpr;
      assert( pSubst->pEList!=0 && pExpr->iColumn<pSubst->pEList->nExpr );
      assert( pExpr->pLeft==0 && pExpr->pRight==0 );
      if( sqlite3ExprIsVector(pCopy) ){
        sqlite3VectorErrorMsg(pSubst->pParse, pCopy);
      }else{
        sqlite3 *db = pSubst->pParse->db;
        pNew = sqlite3ExprDup(db, pCopy, 0);
        if( pNew && (pExpr->flags & EP_FromJoin) ){
          pNew->iRightJoinTable = pExpr->iRightJoinTable;
          pNew->flags |= EP_FromJoin;
        }
        sqlite3ExprDelete(db, pExpr);
        pExpr = pNew;
      }
    }
  }else{
    pExpr->pLeft = substExpr(pSubst, pExpr->pLeft);
    pExpr->pRight = substExpr(pSubst, pExpr->pRight);
    if( ExprHasProperty(pExpr, EP_xIsSelect) ){
      substSelect(pSubst, pExpr->x.pSelect, 1);
    }else{
      substExprList(pSubst, pExpr->x.pList);
    }
  }
  return pExpr;
}
static void substExprList(
  SubstContext *pSubst, /* Description of the substitution */
  ExprList *pList       /* List to scan and in which to make substitutes */


){
  int i;
  if( pList==0 ) return;
  for(i=0; i<pList->nExpr; i++){
    pList->a[i].pExpr = substExpr(pSubst, pList->a[i].pExpr);
  }
}
static void substSelect(
  SubstContext *pSubst, /* Description of the substitution */
  Select *p,            /* SELECT statement in which to make substitutions */


  int doPrior           /* Do substitutes on p->pPrior too */
){
  SrcList *pSrc;
  struct SrcList_item *pItem;
  int i;
  if( !p ) return;
  do{
    substExprList(pSubst, p->pEList);
    substExprList(pSubst, p->pGroupBy);
    substExprList(pSubst, p->pOrderBy);
    p->pHaving = substExpr(pSubst, p->pHaving);
    p->pWhere = substExpr(pSubst, p->pWhere);
    pSrc = p->pSrc;
    assert( pSrc!=0 );
    for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
      substSelect(pSubst, pItem->pSelect, 1);
      if( pItem->fg.isTabFunc ){
        substExprList(pSubst, pItem->u1.pFuncArg);
      }
    }
  }while( doPrior && (p = p->pPrior)!=0 );
}
#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */

#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
................................................................................
      );
      assert( pParent->pGroupBy==0 );
      pParent->pGroupBy = sqlite3ExprListDup(db, pSub->pGroupBy, 0);
    }else{
      pParent->pWhere = sqlite3ExprAnd(db, pWhere, pParent->pWhere);
    }
    if( db->mallocFailed==0 ){
      SubstContext x;
      x.pParse = pParse;
      x.iTable = iParent;
      x.pEList = pSub->pEList;
      substSelect(&x, pParent, 0);
    }
  
    /* The flattened query is distinct if either the inner or the
    ** outer query is distinct. 
    */
    pParent->selFlags |= pSub->selFlags & SF_Distinct;
  
................................................................................
    nChng += pushDownWhereTerms(pParse, pSubq, pWhere->pRight, iCursor);
    pWhere = pWhere->pLeft;
  }
  if( ExprHasProperty(pWhere,EP_FromJoin) ) return 0; /* restriction 5 */
  if( sqlite3ExprIsTableConstant(pWhere, iCursor) ){
    nChng++;
    while( pSubq ){
      SubstContext x;
      pNew = sqlite3ExprDup(pParse->db, pWhere, 0);
      x.pParse = pParse;
      x.iTable = iCursor;
      x.pEList = pSubq->pEList;
      pNew = substExpr(&x, pNew);
      pSubq->pWhere = sqlite3ExprAnd(pParse->db, pSubq->pWhere, pNew);
      pSubq = pSubq->pPrior;
    }
  }
  return nChng;
}
#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */