/*
** Walk all expressions associated with SELECT statement p. Do
** not invoke the SELECT callback on p, but do (of course) invoke
** any expr callbacks and SELECT callbacks that come from subqueries.
** Return WRC_Abort or WRC_Continue.
*/
int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){
if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort;
if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort;
if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort;
if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort;
if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort;
if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort;
if( sqlite3WalkExpr(pWalker, p->pOffset) ) return WRC_Abort;
return WRC_Continue;
}
/*
** Walk an expression tree. Invoke the callback once for each node
** of the expression, while decending. (In other words, the callback
** is invoked before visiting children.)
**
** The return value from the callback should be one of the WRC_*
** constants to specify how to proceed with the walk.
**
** WRC_Continue Continue descending down the tree.
**
** WRC_Prune Do not descend into child nodes. But allow
** the walk to continue with sibling nodes.
**
** WRC_Abort Do no more callbacks. Unwind the stack and
** return the top-level walk call.
**
** The return value from this routine is WRC_Abort to abandon the tree walk
** and WRC_Continue to continue.
*/
int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){
int rc;
if( pExpr==0 ) return WRC_Continue;
rc = pWalker->xExprCallback(pWalker, pExpr);
if( rc==WRC_Continue ){
if( sqlite3WalkExpr(pWalker, pExpr->pLeft) ) return WRC_Abort;
if( sqlite3WalkExpr(pWalker, pExpr->pRight) ) return WRC_Abort;
if( sqlite3WalkExprList(pWalker, pExpr->pList) ) return WRC_Abort;
if( sqlite3WalkSelect(pWalker, pExpr->pSelect) ){
return WRC_Abort;
}
}
return rc & WRC_Abort;
}
static void incrAggFunctionDepth(Expr *pExpr, int N){
if( N>0 ){
Walker w;
memset(&w, 0, sizeof(w));
w.xExprCallback = incrAggDepth;
w.u.i = N;
sqlite3WalkExpr(&w, pExpr);
}
}
int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){
int rc;
if( pExpr==0 ) return WRC_Continue;
testcase( ExprHasProperty(pExpr, EP_TokenOnly) );
testcase( ExprHasProperty(pExpr, EP_Reduced) );
rc = pWalker->xExprCallback(pWalker, pExpr);
if( rc==WRC_Continue
&& !ExprHasAnyProperty(pExpr,EP_TokenOnly) ){
if( sqlite3WalkExpr(pWalker, pExpr->pLeft) ) return WRC_Abort;
if( sqlite3WalkExpr(pWalker, pExpr->pRight) ) return WRC_Abort;
if( ExprHasProperty(pExpr, EP_xIsSelect) ){
if( sqlite3WalkSelect(pWalker, pExpr->x.pSelect) ) return WRC_Abort;
}else{
if( sqlite3WalkExprList(pWalker, pExpr->x.pList) ) return WRC_Abort;
}
}
return rc & WRC_Abort;
}
/*
** Call sqlite3WalkExpr() for every expression in list p or until
** an abort request is seen.
*/
int sqlite3WalkExprList(Walker *pWalker, ExprList *p){
int i, rc = WRC_Continue;
struct ExprList_item *pItem;
if( p ){
for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){
if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort;
}
}
return rc & WRC_Continue;
}
/*
** 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 NC_HasAgg flag 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. */
){
u8 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->ncFlags & NC_HasAgg;
pNC->ncFlags &= ~NC_HasAgg;
memset(&w, 0, sizeof(w));
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 || w.pParse->nErr>0 ){
ExprSetProperty(pExpr, EP_Error);
}
if( pNC->ncFlags & NC_HasAgg ){
ExprSetProperty(pExpr, EP_Agg);
}else if( savedHasAgg ){
pNC->ncFlags |= NC_HasAgg;
}
return ExprHasProperty(pExpr, EP_Error);
}
