The suggested fix and the currently applied fix differ in one important
aspect: The --update option has been dropped.

tldr: Unless --update is broken (and it doesn't appear to be), it should
be included in the fix as it reduces run time quite significantly.

To estimate the effect of --update I tried installing a number of small
apps (e.g. htop) and running the command: update-apt-xapian-index
--update (with default niceness). The time required to perform this
update varied from about 40 seconds to almost 3 times that. The update
process appears to be split into three main components:

- Reading translations for all ubuntu repos in use (security_universe, 
updates_restricted, main, universe, partner, multiverse, etc).
- Reading xapian index.
- Updating xapian index.

When a complete rebuild is performed, the index doesn't need to be read
(and isn't).

In terms of time, the first and second steps are fairly constant, while
the updating bit varies wildly with no pattern I was able to determine
(from about 10 to 60 seconds).

Reading the index was quick, about 5 seconds.

The translations part, which I assume is basically fetching complete
descriptions of all packages installed, is rather slow even on a fast
internet connection. On my system, it took a consistent 25 seconds.

Without debating the merits of the index and its use, there are
certainly a number of optimizations that could be made. Even without
touching the process itself, just using the incremental update feature
cuts run time significantly with no apparent downside.

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https://bugs.launchpad.net/bugs/363695

Title:
  update-apt-xapian-index uses too much CPU and memory

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