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XPath: Optimize predicate evaluation

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If the requested evaluation mode is not _all, we can use this mode for the
last predicate/filter expression and exit early.

git-svn-id: https://pugixml.googlecode.com/svn/trunk@1073 99668b35-9821-0410-8761-19e4c4f06640
This commit is contained in:
Arseny Kapoulkine 2014-10-22 03:33:37 +00:00
parent 28d24e5b6c
commit 4a7762af9d
1 changed files with 24 additions and 7 deletions
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31
src/pugixml.cpp
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@ -8405,6 +8405,11 @@ PUGI__NS_BEGIN
return false; return false;
} }
static bool eval_once(bool forward, nodeset_eval_t eval)
{
return forward ? eval != nodeset_eval_all : eval == nodeset_eval_any;
}
template <class Comp> static bool compare_rel(xpath_ast_node* lhs, xpath_ast_node* rhs, const xpath_context& c, const xpath_stack& stack, const Comp& comp) template <class Comp> static bool compare_rel(xpath_ast_node* lhs, xpath_ast_node* rhs, const xpath_context& c, const xpath_stack& stack, const Comp& comp)
{ {
xpath_value_type lt = lhs->rettype(), rt = rhs->rettype(); xpath_value_type lt = lhs->rettype(), rt = rhs->rettype();
@ -8476,7 +8481,7 @@ PUGI__NS_BEGIN
} }
} }
static void apply_predicate(xpath_node_set_raw& ns, size_t first, xpath_ast_node* expr, const xpath_stack& stack) static void apply_predicate(xpath_node_set_raw& ns, size_t first, xpath_ast_node* expr, const xpath_stack& stack, bool once)
{ {
assert(ns.size() >= first); assert(ns.size() >= first);
@ -8493,22 +8498,32 @@ PUGI__NS_BEGIN
if (expr->rettype() == xpath_type_number) if (expr->rettype() == xpath_type_number)
{ {
if (expr->eval_number(c, stack) == i) if (expr->eval_number(c, stack) == i)
{
*last++ = *it; *last++ = *it;
if (once) break;
}
} }
else if (expr->eval_boolean(c, stack)) else if (expr->eval_boolean(c, stack))
{
*last++ = *it; *last++ = *it;
if (once) break;
}
} }
ns.truncate(last); ns.truncate(last);
} }
void apply_predicates(xpath_node_set_raw& ns, size_t first, const xpath_stack& stack) void apply_predicates(xpath_node_set_raw& ns, size_t first, const xpath_stack& stack, nodeset_eval_t eval)
{ {
if (ns.size() == first) return; if (ns.size() == first) return;
bool last_once = eval_once(ns.type() == xpath_node_set::type_sorted, eval);
for (xpath_ast_node* pred = _right; pred; pred = pred->_next) for (xpath_ast_node* pred = _right; pred; pred = pred->_next)
{ {
apply_predicate(ns, first, pred->_left, stack); apply_predicate(ns, first, pred->_left, stack, !pred->_next && last_once);
} }
} }
@ -8920,7 +8935,7 @@ PUGI__NS_BEGIN
bool once = bool once =
(axis == axis_attribute && _test == nodetest_name) (axis == axis_attribute && _test == nodetest_name)
? true ? true
: !_right && (axis_reverse ? eval == nodeset_eval_any : eval != nodeset_eval_all); : !_right && eval_once(!axis_reverse, eval);
xpath_node_set_raw ns; xpath_node_set_raw ns;
ns.set_type(axis_reverse ? xpath_node_set::type_sorted_reverse : xpath_node_set::type_sorted); ns.set_type(axis_reverse ? xpath_node_set::type_sorted_reverse : xpath_node_set::type_sorted);
@ -8940,13 +8955,13 @@ PUGI__NS_BEGIN
if (axis != axis_self && size != 0) ns.set_type(xpath_node_set::type_unsorted); if (axis != axis_self && size != 0) ns.set_type(xpath_node_set::type_unsorted);
step_fill(ns, *it, stack.result, once, v); step_fill(ns, *it, stack.result, once, v);
apply_predicates(ns, size, stack); apply_predicates(ns, size, stack, eval);
} }
} }
else else
{ {
step_fill(ns, c.n, stack.result, once, v); step_fill(ns, c.n, stack.result, once, v);
apply_predicates(ns, 0, stack); apply_predicates(ns, 0, stack, eval);
} }
// child, attribute and self axes always generate unique set of nodes // child, attribute and self axes always generate unique set of nodes
@ -9581,7 +9596,9 @@ PUGI__NS_BEGIN
// either expression is a number or it contains position() call; sort by document order // either expression is a number or it contains position() call; sort by document order
if (_type == ast_filter) set.sort_do(); if (_type == ast_filter) set.sort_do();
apply_predicate(set, 0, _right, stack); bool once = eval_once(set.type() == xpath_node_set::type_sorted, eval);
apply_predicate(set, 0, _right, stack, once);
return set; return set;
} }