Postgresql is very bad at creating statistics for jsonb
columns. The result is that the query planer tends to
use JIT for queries with a where over 'info' even when
there is an index.
The BDD tests cannot make assumptions about the structure of the
word table anymore because it depends on the tokenizer. Use more
abstract descriptions instead that ask for specific kinds of
tokens.
Requires a second wrapper class for the word table with the new
layout. This class is interface-compatible, so that later when
the ICU tokenizer becomes the default, all tests that depend on
behaviour of the default tokenizer can be switched to the other
wrapper.
The table now directly reflects the different token types.
Extra information is saved in a json structure that may be
dynamically extended in the future without affecting the
table layout.
Moving the logic for extending the SearchDescription into the
token classes splits up the code and makes it more readable.
More importantly: it allows tokenizer to define custom token
classes in the future.
The token string is only required by the PartialToken type, so
it can simply save the token string internally. No need to pass
it to every type.
Also moves the check for multi-word partials to the token loader
code in the tokenizer. Multi-word partials can only happen with
the legacy tokenizer and when the database was loaded with an
older version of Nominatim. No need to keep the check for
everybody.
Moves token and phrase position and phrase type into a separate
class that is handed in when assembling the search description.
This drastically reduces the number of parameters for the function
to extend the search descriptions and gives us more flexibility
in the future for more complex positional analysis.
Full-word tokens are no longer marked by a space at the
beginning of the token. Use the new Partial token category
instead. This removes a couple of special casing, we don't
really need.
The word table still has the space for compatibility reasons,
so the tokenizer code needs to get rid of it when loading the
tokens.
