First select a period on Documents view.

       Then compute a graph chosing one distance (distributional or
       conditional).

       Then in Graph Explorer view (TinaWebJS), user can get colors of
       node with growth attributes.

       Red nodes are increasing.
       Yellow nodes are decreasing.

       Growth computed with previous period which is equal to the
       selected period in duration (but before).

       TODO: make some tests with Users to validate the fact that
       previous period is not all the corpus but the selected period.

    - [OLD] Performance regression
        -> lengthening and slowing the toolchain queue
        -> 2 secondes on 21 Europresse, documents is too much for instance)
    - [OLD] Some ngrams included whereas there are not in the corpus
    + [NEW] Clarity in the query
    + [NEW] Improved: 2000 ms before less than 500 ms after (factor 4
    optimization on a very small corpus); should be ok in bigger corpora

New behavior of the query tested with real corpus and this simple
example; copy paste these lines in test.sql and run it in a test
database (createdb test).

-- let be:

drop table nodes_ngrams;
drop table synonyms;
drop table ngrams;
drop table nodes;

create table nodes (
    id serial PRIMARY KEY not null
);

create table ngrams (
    id serial PRIMARY KEY not null,
    text varchar(50)
);

create table synonyms (
    id serial PRIMARY KEY not null,
    node_id INTEGER not null,
    ngram1_id INTEGER not null references ngrams(id),
    ngram2_id INTEGER not null references ngrams(id)
);

create table nodes_ngrams (
    id serial PRIMARY KEY not null,
    node_id INTEGER not null references nodes(id),
    ngram_id INTEGER not null references ngrams(id)
);

insert into nodes (id) values(1);
insert into nodes (id) values(2);
insert into nodes (id) values(3);

insert into ngrams (text) values('object');
insert into ngrams (text) values('table');
insert into ngrams (text) values('animal');
insert into ngrams (text) values('cat');
insert into ngrams (text) values('dog');
insert into ngrams (text) values('other');
insert into ngrams (text) values('abc');
insert into ngrams (text) values('xyz');
--select * from ngrams;
---- id |  text
--------+--------
----  1 | object
----  2 | table
----  3 | animal
----  4 | cat
----  5 | dog
----  6 | other
----  7 | abc
----  8 | xyz

insert into synonyms (node_id,ngram1_id,ngram2_id) values(1,1,2);
insert into synonyms (node_id,ngram1_id,ngram2_id) values(1,3,4);
insert into synonyms (node_id,ngram1_id,ngram2_id) values(1,3,5);
--select * from synonyms;
-- id | node_id | ngram1_id | ngram2_id
------+---------+-----------+-----------
--  1 |       1 |         1 |         2
--  2 |       1 |         3 |         4
--  3 |       1 |         3 |         5

insert into nodes_ngrams (node_id, ngram_id) values(1,1);
insert into nodes_ngrams (node_id, ngram_id) values(1,6);
insert into nodes_ngrams (node_id, ngram_id) values(1,2);
insert into nodes_ngrams (node_id, ngram_id) values(2,4);
insert into nodes_ngrams (node_id, ngram_id) values(2,5);
insert into nodes_ngrams (node_id, ngram_id) values(3,4);
insert into nodes_ngrams (node_id, ngram_id) values(3,5);
insert into nodes_ngrams (node_id, ngram_id) values(3,6);
--select * from nodes_ngrams;
-- id | node_id | ngram_id
------+---------+----------
--  1 |       1 |        1
--  2 |       1 |        6
--  3 |       1 |        2
--  4 |       2 |        4
--  5 |       2 |        5
--  6 |       3 |        4
--  7 |       3 |        5
--  8 |       3 |        6

select n1.ngram_id, n2.ngram_id, count(*)
from nodes n
INNER JOIN nodes_ngrams n1 ON n1.node_id = n.id
INNER JOIN nodes_ngrams n2 ON n2.node_id = n.id
where
n1.ngram_id <= n2.ngram_id
--AND
--n1.node_id = n2.node_id
group by 1,2
order BY n1.ngram_id ASC
;
-- ngram_id | ngram_id | count
------------+----------+-------
--        5 |        6 |     1
--        1 |        6 |     1
--        4 |        6 |     1
--        2 |        2 |     1
--        4 |        4 |     2
--        1 |        1 |     1
--        1 |        2 |     1
--        6 |        6 |     2
--        2 |        6 |     1
--        4 |        5 |     2
--        5 |        5 |     2
--(11 lignes)

select coalesce(n11.id, n1.ngram_id), coalesce(n22.id,n2.ngram_id), count(*)
from nodes n
INNER JOIN nodes_ngrams n1 ON n1.node_id = n.id
LEFT JOIN synonyms s1 on n1.ngram_id = s1.ngram2_id AND s1.node_id=1
LEFT JOIN ngrams n11 on s1.ngram1_id = n11.id

INNER JOIN nodes_ngrams n2 ON n2.node_id = n.id
LEFT JOIN synonyms s2 on n2.ngram_id = s2.ngram2_id AND s2.node_id=1
LEFT JOIN ngrams n22 on s2.ngram1_id = n22.id
where
n1.ngram_id <= n2.ngram_id
AND
n1.node_id = n2.node_id
group by 1,2
;
-- coalesce | coalesce | count
------------+----------+-------
--        1 |        6 |     2
--        3 |        3 |     6
--        1 |        1 |     3
--        3 |        6 |     2
--        6 |        6 |     2
--(5 lignes)
--> les sommes comptées correspondent

[COMMUNITY] Adding code of Conduct (each developer participating to the development has to sign it).