Optimize xml_path and xml_find_all for large node sets#478
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Closes #477
This PR improves performance for large node sets in two places:
xml_path()now caches reusable ancestor paths while processing anxml_nodeset, avoiding repeated parent walks and repeated construction of shared path prefixes.xml_find_all.xml_node()avoids an unnecessary duplicate pass for single-context XPath node sets and materializesxml_noderesults with less per-node overhead.The intended semantics are unchanged.
Tests added:
xml_path()output is identical to callingxml_path()on each node individuallyxml_find_all()XPath node sets remain unique even for union expressionsImplementation note:
Some repetition in the path occurrence logic is intentional. I tested a more compact shared abstraction for sibling occurrence counting, but it made the hot loop noticeably slower for large node sets. The current version keeps those cases explicit to preserve the performance gain while matching
xmlGetNodePath()semantics.Local checks:
testthat::test_dir("tests/testthat"): PASSR CMD build --no-manual --no-build-vignettes .: OK_R_CHECK_FORCE_SUGGESTS_=false R CMD check --no-manual --no-build-vignettes xml2_1.5.2.tar.gz: OK, with only vignette warnings due to--no-build-vignettes