Optimized xmlXPathNodeCollectAndTest() and xmlXPathNodeCollectAndTestNth()
* xpath.c: Optimized xmlXPathNodeCollectAndTest() and
xmlXPathNodeCollectAndTestNth() to evaluate a compound
traversal of 2 axes when we have a "//foo" expression.
This is done with a rewrite of the XPath AST in
xmlXPathRewriteDOSExpression(); I added an additional field
to xmlXPathStepOp for this (but the field's name should be
changed). The mechanism: the embracing descendant-or-self
axis traversal (also optimized to return only nodes which
can hold elements), will produce context nodes for the
inner traversal of the child axis. This way we avoid a full
node-collecting traversal of the descendant-or-self axis.
Some tests indicate that this can reduce execution time of
"//foo" to 50%. Together with the XPath object cache this
all significantly speeds up libxslt.
2 files changed