Raymond Hill adabb56dc9

Do not store impossible to match filters in HNTrie ...

Consider the two following filters:

    example.com
    www.example.com

This commit make it so that if the first filter is
already present in a given HNTrie, the second filter
will not be stored, since HNTrie will _always_
return the first filter as a match whenever the
hostname to match is example.com or any subdomain
of example.com.

The detection of such pointless filters is
virtually free when adding a hostname to an HNTrie
instance (given how data is stored in the trie), so
in practice no overhead is incurred to detect such
pointless filters.

The ability to ignore impossible to match filters
in HNTrie instances will _especially_ benefit those
using large hosts files.

Examples of how this helps using real configurations:

- Default lists:
  444 filters out of 100,382 were ignored as a result
  of this commit.

- Default lists + "Energized Ultimate Protection":
  283,669 filters out of 903,235 were ignored as a
  result of this commit.

Side note: There was no measurable difference between
the two configurations above in the performance of
the matching algorithm as reported by the built-in
benchmark tool.

2019-04-29 13:15:16 -04:00

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