Subject: RE: [xsl] How to efficiently remove "a" nodes with no "b" descend ants From: "FINLEY, Mike" <Mike.FINLEY@xxxxxxxxxx> Date: Fri, 9 Mar 2001 11:35:58 -0000 |
thanks! Its useful to know what we can realistically expect an optimiser to do, and how to help one along. mike -----Original Message----- From: Michael Kay [mailto:mhkay@xxxxxxxxxxxx] Sent: 09 March 2001 10:33 To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx Subject: RE: [xsl] How to efficiently remove "a" nodes with no "b" descend ants > If I say > > > <xsl:template match="a[not(.//b)]"/> > > then all the descendants of "a" are checked for "b" elements. Let's > have a closer look at the input structure. > This presupposes that the XSLT processor you are using does > no optimisation, which may or may not be true. > Optimizers look for "quick wins", constructs that are used sufficiently often to be worth treating specially, and I suspect this isn't one of them. Generally, it's bad news to put a complex test like this into a match pattern, because there is little alternative to testing each node selected by <apply-templates> against this pattern; there is more scope to optimise a node-set expression than a pattern. ... Mike Kay XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list ___________________________________________________________________________ This email is confidential and intended solely for the use of the individual to whom it is addressed. Any views or opinions presented are solely those of the author and do not necessarily represent those of Sema. If you are not the intended recipient, be advised that you have received this email in error and that any use, dissemination, forwarding, printing, or copying of this email is strictly prohibited. If you have received this email in error please notify the Sema UK Helpdesk by telephone on +44 (0) 121 627 5600. ___________________________________________________________________________ XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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