Re: [xslt] XSLT compilation is slow for big XSLTs

[Nick Wellnhofer <wellnhofer aevum de>]

On 20/08/2015 19:21, Christian Ceelen wrote:
> Ok. I think i found the answer by trial and error myself. I was not able to
> look up the named templates in the hash table for the (pre-) compiled templates.
>
> So i followed Nick's suggest and came up with this first draft:
> https://github.com/GNOME/libxslt/pull/1

Some quick comments:

- It's nice that you create the hash lazily.
- The helper function xsltHasNamedTemplate doesn't seem to be
  necessary since it's used only once.
- xmlHashCreate(1024) creates a hash table with 1024 initial slots.
  This value should be reduced to something sensible like 4.

I think reordering structs in xsltInternals.h doesn't break ABI compatibility. 
So `namedTemplatesHash` could be moved to the other template fields. But I'm 
not 100% sure.

> I tested locally and didn't get any surprises. I also created a simple test
> with 2 named templates that have the same name to test for collision
> detection. The new code behaves in that case as the previous one. But so far I
> have no idea yet where and how to add it to the tests in the test suite as
> this is a test for failure detection.

Put your test files in:

- tests/REC/test-6-2.xml
- tests/REC/test-6-2.xsl

Then run `make tests`. This will create files

- tests/REC/test-6-2.out
- tests/REC/test-6-2.err (if there's stderr output)

Inspect the contents of the `.out` and `.err` files. If everything's OK, add 
them to version control.

> Looking at a second glance at the imports.c and xsltFindTemplate i think it
> would be worthwhile to add the new function i created for lookup in the hash
> table in the file imports.c and try to encapsulate the behavior there. Do you
> think i should refactor the code in that direction?

I don't think it's necessary to add any helper functions. But please change 
the lookup code in imports.c to make use of the named templates hash.

Nick