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Bug #1740
closed
Performance regression for $x[$i]
Start date:
2013-04-24
Due date:
% Done:
100%
Estimated time:
Legacy ID:
Applies to branch:
Fix Committed on Branch:
Fixed in Maintenance Release:
Platforms:
Description
Saxon 9.5 shows a performance regression when evaluating an expression such as
for $i in 1 to $n return $x[$i]
The cause is that the subscript expression is evaluated using a TailIterator, whose strategy depends on whether the iterator for $x is "grounded" or not. In this case the iterator is a ProgressiveIterator, which 9.4 decides is grounded, and 9.5 decides is not. In this instance the 9.4 strategy works better, despite forcing $x to be eagerly evaluated.
Reported by Gunther Rademacher on saxon-help list. See also MHK response on list.
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