resolve.c

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** then convert that term into a copy of the corresponding result set
** column.
**
** If any errors are detected, add an error message to pParse and
** return non-zero.  Return zero if no errors are seen.
*/
int sqlite3ResolveOrderGroupBy(
  Parse *pParse,        /* Parsing context.  Leave error messages here */
  Select *pSelect,      /* The SELECT statement containing the clause */
  ExprList *pOrderBy,   /* The ORDER BY or GROUP BY clause to be processed */
  const char *zType     /* "ORDER" or "GROUP" */
){
  int i;
  sqlite3 *db = pParse->db;
  ExprList *pEList;
  struct ExprList_item *pItem;

  if( pOrderBy==0 || pParse->db->mallocFailed ) return 0;
#if SQLITE_MAX_COLUMN
  if( pOrderBy->nExpr>db->aLimit[SQLITE_LIMIT_COLUMN] ){
    sqlite3ErrorMsg(pParse, "too many terms in %s BY clause", zType);
    return 1;
  }
#endif
  pEList = pSelect->pEList;
  assert( pEList!=0 );  /* sqlite3SelectNew() guarantees this */
  for(i=0, pItem=pOrderBy->a; i<pOrderBy->nExpr; i++, pItem++){
    if( pItem->iCol ){
      if( pItem->iCol>pEList->nExpr ){
        resolveOutOfRangeError(pParse, zType, i+1, pEList->nExpr);
        return 1;
      }
      resolveAlias(pParse, pEList, pItem->iCol-1, pItem->pExpr, zType);
    }
  }
  return 0;
}

/*
** pOrderBy is an ORDER BY or GROUP BY clause in SELECT statement pSelect.
** The Name context of the SELECT statement is pNC.  zType is either
** "ORDER" or "GROUP" depending on which type of clause pOrderBy is.
**
** This routine resolves each term of the clause into an expression.
** If the order-by term is an integer I between 1 and N (where N is the
** number of columns in the result set of the SELECT) then the expression
** in the resolution is a copy of the I-th result-set expression.  If
** the order-by term is an identify that corresponds to the AS-name of
** a result-set expression, then the term resolves to a copy of the
** result-set expression.  Otherwise, the expression is resolved in
** the usual way - using sqlite3ResolveExprNames().
**
** This routine returns the number of errors.  If errors occur, then
** an appropriate error message might be left in pParse.  (OOM errors
** excepted.)
*/
static int resolveOrderGroupBy(
  NameContext *pNC,     /* The name context of the SELECT statement */
  Select *pSelect,      /* The SELECT statement holding pOrderBy */
  ExprList *pOrderBy,   /* An ORDER BY or GROUP BY clause to resolve */
  const char *zType     /* Either "ORDER" or "GROUP", as appropriate */
){
  int i;                         /* Loop counter */
  int iCol;                      /* Column number */
  struct ExprList_item *pItem;   /* A term of the ORDER BY clause */
  Parse *pParse;                 /* Parsing context */
  int nResult;                   /* Number of terms in the result set */

  if( pOrderBy==0 ) return 0;
  nResult = pSelect->pEList->nExpr;
  pParse = pNC->pParse;
  for(i=0, pItem=pOrderBy->a; i<pOrderBy->nExpr; i++, pItem++){
    Expr *pE = pItem->pExpr;
    iCol = resolveAsName(pParse, pSelect->pEList, pE);
    if( iCol<0 ){
      return 1;  /* OOM error */
    }
    if( iCol>0 ){
      /* If an AS-name match is found, mark this ORDER BY column as being
      ** a copy of the iCol-th result-set column.  The subsequent call to
      ** sqlite3ResolveOrderGroupBy() will convert the expression to a
      ** copy of the iCol-th result-set expression. */
      pItem->iCol = iCol;
      continue;
    }
    if( sqlite3ExprIsInteger(pE, &iCol) ){
      /* The ORDER BY term is an integer constant.  Again, set the column
      ** number so that sqlite3ResolveOrderGroupBy() will convert the
      ** order-by term to a copy of the result-set expression */
      if( iCol<1 ){
        resolveOutOfRangeError(pParse, zType, i+1, nResult);
        return 1;
      }
      pItem->iCol = iCol;
      continue;
    }

    /* Otherwise, treat the ORDER BY term as an ordinary expression */
    pItem->iCol = 0;
    if( sqlite3ResolveExprNames(pNC, pE) ){
      return 1;
    }
  }
  return sqlite3ResolveOrderGroupBy(pParse, pSelect, pOrderBy, zType);
}

/*
** Resolve names in the SELECT statement p and all of its descendents.
*/
static int resolveSelectStep(Walker *pWalker, Select *p){
  NameContext *pOuterNC;  /* Context that contains this SELECT */
  NameContext sNC;        /* Name context of this SELECT */
  int isCompound;         /* True if p is a compound select */
  int nCompound;          /* Number of compound terms processed so far */
  Parse *pParse;          /* Parsing context */
  ExprList *pEList;       /* Result set expression list */
  int i;                  /* Loop counter */
  ExprList *pGroupBy;     /* The GROUP BY clause */
  Select *pLeftmost;      /* Left-most of SELECT of a compound */
  sqlite3 *db;            /* Database connection */
  

  assert( p!=0 );
  if( p->selFlags & SF_Resolved ){
    return WRC_Prune;
  }
  pOuterNC = pWalker->u.pNC;
  pParse = pWalker->pParse;
  db = pParse->db;

  /* Normally sqlite3SelectExpand() will be called first and will have
  ** already expanded this SELECT.  However, if this is a subquery within
  ** an expression, sqlite3ResolveExprNames() will be called without a
  ** prior call to sqlite3SelectExpand().  When that happens, let
  ** sqlite3SelectPrep() do all of the processing for this SELECT.
  ** sqlite3SelectPrep() will invoke both sqlite3SelectExpand() and
  ** this routine in the correct order.
  */
  if( (p->selFlags & SF_Expanded)==0 ){
    sqlite3SelectPrep(pParse, p, pOuterNC);
    return (pParse->nErr || db->mallocFailed) ? WRC_Abort : WRC_Prune;
  }

  isCompound = p->pPrior!=0;
  nCompound = 0;
  pLeftmost = p;
  while( p ){
    assert( (p->selFlags & SF_Expanded)!=0 );
    assert( (p->selFlags & SF_Resolved)==0 );
    p->selFlags |= SF_Resolved;

    /* Resolve the expressions in the LIMIT and OFFSET clauses. These
    ** are not allowed to refer to any names, so pass an empty NameContext.
    */
    memset(&sNC, 0, sizeof(sNC));
    sNC.pParse = pParse;
    if( sqlite3ResolveExprNames(&sNC, p->pLimit) ||
        sqlite3ResolveExprNames(&sNC, p->pOffset) ){
      return WRC_Abort;
    }
  
    /* Set up the local name-context to pass to sqlite3ResolveExprNames() to
    ** resolve the result-set expression list.
    */
    sNC.allowAgg = 1;
    sNC.pSrcList = p->pSrc;
    sNC.pNext = pOuterNC;
  
    /* Resolve names in the result set. */
    pEList = p->pEList;
    assert( pEList!=0 );
    for(i=0; i<pEList->nExpr; i++){
      Expr *pX = pEList->a[i].pExpr;
      if( sqlite3ResolveExprNames(&sNC, pX) ){
        return WRC_Abort;
      }
    }
  
    /* Recursively resolve names in all subqueries
    */
    for(i=0; i<p->pSrc->nSrc; i++){
      struct SrcList_item *pItem = &p->pSrc->a[i];
      if( pItem->pSelect ){
        const char *zSavedContext = pParse->zAuthContext;
        if( pItem->zName ) pParse->zAuthContext = pItem->zName;
        sqlite3ResolveSelectNames(pParse, pItem->pSelect, &sNC);
        pParse->zAuthContext = zSavedContext;
        if( pParse->nErr || db->mallocFailed ) return WRC_Abort;
      }
    }
  
    /* If there are no aggregate functions in the result-set, and no GROUP BY 
    ** expression, do not allow aggregates in any of the other expressions.
    */
    assert( (p->selFlags & SF_Aggregate)==0 );
    pGroupBy = p->pGroupBy;
    if( pGroupBy || sNC.hasAgg ){
      p->selFlags |= SF_Aggregate;
    }else{
      sNC.allowAgg = 0;
    }
  
    /* If a HAVING clause is present, then there must be a GROUP BY clause.
    */
    if( p->pHaving && !pGroupBy ){
      sqlite3ErrorMsg(pParse, "a GROUP BY clause is required before HAVING");
      return WRC_Abort;
    }
  
    /* Add the expression list to the name-context before parsing the
    ** other expressions in the SELECT statement. This is so that
    ** expressions in the WHERE clause (etc.) can refer to expressions by
    ** aliases in the result set.
    **
    ** Minor point: If this is the case, then the expression will be
    ** re-evaluated for each reference to it.
    */
    sNC.pEList = p->pEList;
    if( sqlite3ResolveExprNames(&sNC, p->pWhere) ||
       sqlite3ResolveExprNames(&sNC, p->pHaving)
    ){
      return WRC_Abort;
    }

    /* The ORDER BY and GROUP BY clauses may not refer to terms in
    ** outer queries 
    */
    sNC.pNext = 0;
    sNC.allowAgg = 1;

    /* Process the ORDER BY clause for singleton SELECT statements.
    ** The ORDER BY clause for compounds SELECT statements is handled
    ** below, after all of the result-sets for all of the elements of
    ** the compound have been resolved.
    */
    if( !isCompound && resolveOrderGroupBy(&sNC, p, p->pOrderBy, "ORDER") ){
      return WRC_Abort;
    }
    if( db->mallocFailed ){
      return WRC_Abort;
    }
  
    /* Resolve the GROUP BY clause.  At the same time, make sure 
    ** the GROUP BY clause does not contain aggregate functions.
    */
    if( pGroupBy ){
      struct ExprList_item *pItem;
    
      if( resolveOrderGroupBy(&sNC, p, pGroupBy, "GROUP") || db->mallocFailed ){
        return WRC_Abort;
      }
      for(i=0, pItem=pGroupBy->a; i<pGroupBy->nExpr; i++, pItem++){
        if( ExprHasProperty(pItem->pExpr, EP_Agg) ){
          sqlite3ErrorMsg(pParse, "aggregate functions are not allowed in "
              "the GROUP BY clause");
          return WRC_Abort;
        }
      }
    }

    /* Advance to the next term of the compound
    */
    p = p->pPrior;
    nCompound++;
  }

  /* Resolve the ORDER BY on a compound SELECT after all terms of
  ** the compound have been resolved.
  */
  if( isCompound && resolveCompoundOrderBy(pParse, pLeftmost) ){
    return WRC_Abort;
  }

  return WRC_Prune;
}

/*
** This routine walks an expression tree and resolves references to
** table columns and result-set columns.  At the same time, do error
** checking on function usage and set a flag if any aggregate functions
** are seen.
**
** To resolve table columns references we look for nodes (or subtrees) of the 
** form X.Y.Z or Y.Z or just Z where
**
**      X:   The name of a database.  Ex:  "main" or "temp" or
**           the symbolic name assigned to an ATTACH-ed database.
**
**      Y:   The name of a table in a FROM clause.  Or in a trigger
**           one of the special names "old" or "new".
**
**      Z:   The name of a column in table Y.
**
** The node at the root of the subtree is modified as follows:
**
**    Expr.op        Changed to TK_COLUMN
**    Expr.pTab      Points to the Table object for X.Y
**    Expr.iColumn   The column index in X.Y.  -1 for the rowid.
**    Expr.iTable    The VDBE cursor number for X.Y
**
**
** To resolve result-set references, look for expression nodes of the
** form Z (with no X and Y prefix) where the Z matches the right-hand
** size of an AS clause in the result-set of a SELECT.  The Z expression
** is replaced by a copy of the left-hand side of the result-set expression.
** Table-name and function resolution occurs on the substituted expression
** tree.  For example, in:
**
**      SELECT a+b AS x, c+d AS y FROM t1 ORDER BY x;
**
** The "x" term of the order by is replaced by "a+b" to render:
**
**      SELECT a+b AS x, c+d AS y FROM t1 ORDER BY a+b;
**
** Function calls are checked to make sure that the function is 
** defined and that the correct number of arguments are specified.
** If the function is an aggregate function, then the pNC->hasAgg is
** set and the opcode is changed from TK_FUNCTION to TK_AGG_FUNCTION.
** If an expression contains aggregate functions then the EP_Agg
** property on the expression is set.
**
** An error message is left in pParse if anything is amiss.  The number
** if errors is returned.
*/
int sqlite3ResolveExprNames( 
  NameContext *pNC,       /* Namespace to resolve expressions in. */
  Expr *pExpr             /* The expression to be analyzed. */
){
  int savedHasAgg;
  Walker w;

  if( pExpr==0 ) return 0;
#if SQLITE_MAX_EXPR_DEPTH>0
  {
    Parse *pParse = pNC->pParse;
    if( sqlite3ExprCheckHeight(pParse, pExpr->nHeight+pNC->pParse->nHeight) ){
      return 1;
    }
    pParse->nHeight += pExpr->nHeight;
  }
#endif
  savedHasAgg = pNC->hasAgg;
  pNC->hasAgg = 0;
  w.xExprCallback = resolveExprStep;
  w.xSelectCallback = resolveSelectStep;
  w.pParse = pNC->pParse;
  w.u.pNC = pNC;
  sqlite3WalkExpr(&w, pExpr);
#if SQLITE_MAX_EXPR_DEPTH>0
  pNC->pParse->nHeight -= pExpr->nHeight;
#endif
  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);
}


/*
** Resolve all names in all expressions of a SELECT and in all
** decendents of the SELECT, including compounds off of p->pPrior,
** subqueries in expressions, and subqueries used as FROM clause
** terms.
**
** See sqlite3ResolveExprNames() for a description of the kinds of
** transformations that occur.
**
** All SELECT statements should have been expanded using
** sqlite3SelectExpand() prior to invoking this routine.
*/
void sqlite3ResolveSelectNames(
  Parse *pParse,         /* The parser context */
  Select *p,             /* The SELECT statement being coded. */
  NameContext *pOuterNC  /* Name context for parent SELECT statement */
){
  Walker w;

  assert( p!=0 );
  w.xExprCallback = resolveExprStep;
  w.xSelectCallback = resolveSelectStep;
  w.pParse = pParse;
  w.u.pNC = pOuterNC;
  sqlite3WalkSelect(&w, p);
}