[Gramps-devel] Performance issue with try/except

[Kees B. <kee...@xs...>]

Hi,

A few days ago I reported problems with scrolling in the people view.
Don pointed at src/DisplayModels/_PeopleModel.py where LRU is used
to speed up certain database lookups. Despite what Don was saying
it is implemented as follows:

    def column_name(self, data, node):
        try:
            name = self.lru_name[node]
        except:
            name = NameDisplay.displayer.raw_sorted_name(data[PeopleModel._NAME_COL])
            self.lru_name[node] = name
        return name

(There are four data items handled this way. One of them slightly more complex.)

Today I read some notes about performance issue with try-except. And I've done
a bit of testing with a small test program. The thing is (just as it is in C++)
try-except is not cheap wrt performance. The following code is (for this snippet)
almost 10 times faster. (Depends a lot on the hit-rate, of course.)

    def column_name(self, data, node):
        if node in self.lru_name:
            name = self.lru_name[node]
        else:
            name = NameDisplay.displayer.raw_sorted_name(data[PeopleModel._NAME_COL])
            self.lru_name[node] = name
        return name

(And this is more or less what Don wrote in his email.)

Now, what does this all mean? Unfortunately not a whole lot. I've changed the code
as described above, but I couldn't see any performance change. Bummer. Then I
tried a version without LRU and even that did not make a change. Just to verify that
my modification were use I placed logging, and the logging was there.

Needless to say I'm puzzled and I wanted to let you know :-)

- Kees