Bug #3563
closed
Pattern schema-element(ITEM)/AUTHOR is not motionless
Applies to branch:
9.8, trunk
Fix Committed on Branch:
9.8, trunk
Fixed in Maintenance Release:
Description
In a streamable schema-aware stylesheet, use of a pattern such as
match="schema-element(ITEM)/AUTHOR"
passes static analysis as a motionless pattern, but fails at execution time saying:
java.lang.UnsupportedOperationException: net.sf.saxon.trans.XPathException: Navigation using child axis is not supported from a streamed input node
It appears to have been compiled as a GeneralNodePattern rather than as an AncestorQualifiedExpression.
It seems that the schema-aware optimization has recognized that there can only be one AUTHOR in an ITEM, and has helpfully rewritten the expression as @schema-element(ITEM)/AUTHOR[1]@, In fact it seems to have done this twice, and changed it to @schema-element(ITEM)/AUTHOR[1][1]@. Adding the [1] is useful for XPath expressions, because it stops searching after finding one AUTHOR, and establishes a more accurate type for the expression; but it's counter-productive for XSLT patterns.
The creation of a FirstItemExpression happens in AxisExpression.checkPlausibility(), line 509.
We can prevent the redundant first(first(X)) by changing this code to special-case the situation where the parent of the AxisExpression is already a FirstItemExpression.
With this change we now get an AncestorQualifiedPattern, but it is still non-streamable because of the [1] predicate.
To suppress the rewrite completely within a pattern, we introduce a switch ExpressionVisitor.optimizeForPatternMatching.
- Priority changed from Low to Normal
- Applies to branch 9.8, trunk added
- Fix Committed on Branch trunk added
Fixed on the development branch.
Test case si-apply-templates-007 added (not yet working)
- Status changed from New to Resolved
- Fix Committed on Branch 9.8 added
Fixed on 9.8 branch and trunk.
New test case is now passing - but on 9.8 it passes when run from the command line, but not from the test driver, because the test driver doesn't handle validation on streamed source documents.
- % Done changed from 0 to 100
Bug fix applied in the Saxon 9.8.0.7 maintenance release.
- Status changed from Resolved to Closed
- Fixed in Maintenance Release 9.8.0.7 added
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