Since page size can be customized let's do a special validation check for
compact encoding. Right now it's redundant since page size is limited by
64k in alloc_string, but that may change in the future.
This allows us to add pi value to restore target support for PI nodes without
increasing the memory usage for other nodes.
Right now the PI node has a separate header that's used for allocated bit;
this allows us to reduce header bitcount in the future.
Previously setting a large page size (i.e. 1M) would cause dynamic string
allocation to assert spuriously. A page size of 64K guarantees that all
offsets fit into 16 bits.
Split number/boolean filtering logic into two functions. This creates an
extra copy of a remove_if-like algorithm, but moves the type check out of
the loop and results in better organized filtering code.
Consolidate test-based dispatch into apply_predicate (which is now a member
function).
This lets us do fewer null pointer checks (making printing 2% faster with -O3)
and removes a lot of function calls (making printing 20% faster with -O0).
To get more benefits from constant predicate/filter optimization we rewrite
[position()=expr] predicates into [expr] for numeric expressions. Right now
the rewrite is only for entire expressions - it may be beneficial to split
complex expressions like [position()=constant and expr] into [constant][expr]
but that is more complicated.
last() does not depend on the node set contents so is "constant" as far as
our optimization is concerned so we can evaluate it once.
Numeric and boolean constant expressions in filters are different in that
to evaluate numeric expressions we need a sorted order, but to evaluate
boolean expressions we don't. The previously implemented optimization adds
an extra sorting step for constant boolean filters that will be more expensive
than redundant computations.
Since constant booleans are sort of an edge case, don't do this optimization.
This allows us to simplify apply_predicate_const to only handle numbers.
Now expression is always _right for filter/predicate nodes to make optimize()
simpler. Additionally we now use predicate metadata to make is_posinv_step()
faster.
This introduces a weak ordering dependency in rewrite rules to optimize() -
classification has to be performed before other optimizations.
If a filter/predicate expression is a constant, we don't need to evaluate it
for every nodeset element - we can evaluate it once and pick the right element
or keep/discard the entire collection.
If the expression is 1, we can early out on first node when evaluating the
node set - queries like following::item[1] are now significantly faster.
Additionally this change refactors filters/predicates to have additional
metadata describing the expression type in _test field that is filled during
optimization.
Note that predicate_constant selection right now is very simple (but captures
most common use cases except for maybe [last()]).
A page can fail to allocate during attribute creation; this case was not
previously handled.
git-svn-id: https://pugixml.googlecode.com/svn/trunk@1080 99668b35-9821-0410-8761-19e4c4f06640
When removing a node or attribute, we know that the parent has at least one
node/attribute so a null pointer check is redundant.
git-svn-id: https://pugixml.googlecode.com/svn/trunk@1078 99668b35-9821-0410-8761-19e4c4f06640
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
Using pointers instead of node/attribute objects allows us to use knowledge
about the tree to guarantee that pointers are not null. This results in
less null checks (10-20% speedup with optimizations enabled) and less
function calls (5x speedup with optimizations disabled).
git-svn-id: https://pugixml.googlecode.com/svn/trunk@1072 99668b35-9821-0410-8761-19e4c4f06640
This should never happen but can improve debugging experience for
work-in-progress changes since that avoids memcpy() into negative memory
space (debugger can't backtrace from failed memcpy since it does not set
up the stack frame).
git-svn-id: https://pugixml.googlecode.com/svn/trunk@1070 99668b35-9821-0410-8761-19e4c4f06640
Some steps relied on step_push rejecting null inputs; this is no longer
the case. Additionally stepping now more rigorously filters null inputs.
git-svn-id: https://pugixml.googlecode.com/svn/trunk@1069 99668b35-9821-0410-8761-19e4c4f06640
Sometimes when evaluating the node set we don't need the entire set and
only need the first element in docorder or any element. In the absence of
iterator support we can still use this information to short-circuit
traversals.
This does not have any effect on straightforward node collection queries,
but frequently improves performance of complex queries with predicates
etc. XMark benchmark gets 15x faster with some queries enjoying 100x
speedup on 10 Mb dataset due to a significant complexity improvement.
git-svn-id: https://pugixml.googlecode.com/svn/trunk@1067 99668b35-9821-0410-8761-19e4c4f06640
Add documentation for xpath_query::evaluate_node and change
select_single_node to select_node in documentation and samples.
git-svn-id: https://pugixml.googlecode.com/svn/trunk@1066 99668b35-9821-0410-8761-19e4c4f06640
select_node is shorter and mistyping nodes as node or vice versa should
not lead to any issues since return types are substantially different.
select_single_node method still works and will be deprecated with an
attribute and removed at some point.
git-svn-id: https://pugixml.googlecode.com/svn/trunk@1065 99668b35-9821-0410-8761-19e4c4f06640
This method is equivalent to xml_node::select_single_node. This makes
select_single_node faster in certain cases by avoiding an allocation and -
more importantly - paves the way for future step optimizations.
git-svn-id: https://pugixml.googlecode.com/svn/trunk@1064 99668b35-9821-0410-8761-19e4c4f06640
