databse: Modify aggr_availability table

Now aggregating the total count of machines in each state (red, yellow
and green) by school and by month (only the last 6 months). This is a
more general and usable version of the previous aggr_availability.
Signed-off-by: Eduardo L. Buratti <elb09@c3sl.ufpr.br>

database/create/004-aggregates.sql

 CREATE TABLE aggr_availability (
-    base_date       DATE NOT NULL,
-    macaddr         MACADDR NOT NULL,
-    project         project_enum DEFAULT 'proinfo' NOT NULL,
-    sch_inep        CHARACTER VARYING(12) NOT NULL,
-    sch_name        CHARACTER VARYING(150) NOT NULL,
-    city            CHARACTER VARYING(100) NOT NULL,
-    state           CHARACTER VARYING(2) NOT NULL,
-    region          CHARACTER VARYING(12) NOT NULL,
-    is_green        SMALLINT NOT NULL DEFAULT 0,
-    is_yellow       SMALLINT NOT NULL DEFAULT 0,
-    is_red          SMALLINT NOT NULL DEFAULT 0
+    sch_id INTEGER NOT NULL REFERENCES dim_school,
+    cit_id INTEGER NOT NULL REFERENCES dim_city,
+    dat_id DATE NOT NULL REFERENCES dim_date,
+    mac_count BIGINT NOT NULL DEFAULT 0,
+    mac_count_red BIGINT NOT NULL DEFAULT 0,
+    mac_count_yellow BIGINT NOT NULL DEFAULT 0,
+    mac_count_green BIGINT NOT NULL DEFAULT 0,
+    project project_enum DEFAULT 'proinfo' NOT NULL,
+    UNIQUE (sch_id, cit_id, dat_id, project)
 );

database/load/005-aggregates.sql

 CREATE OR REPLACE FUNCTION load_aggr_availability() returns void as $$
 DECLARE
     date_it date;
-    i INTEGER;
     start_ts TIMESTAMP;
     total_rows INTEGER;
     cur_rows INTEGER;
@@ -11,15 +10,14 @@ BEGIN
     start_ts = CLOCK_TIMESTAMP();
     total_rows := 0;
 
-    -- remove the index - later we create it again
-    DROP INDEX IF EXISTS aggr_availability_base_date_idx;
-
     -- remove old data
     TRUNCATE TABLE aggr_availability;
 
     -- iterate over past months
-    FOR i IN 0..5 LOOP
-        date_it := CURRENT_DATE - (i *  interval '1 month');
+    FOR date_it IN SELECT (date_trunc('month', generate_series(
+                current_date - interval '4 months',
+                current_date,
+                interval '1 month')) - interval '1 day')::date UNION select current_date LOOP
 
         INSERT INTO aggr_availability
         SELECT
@@ -62,9 +60,6 @@ BEGIN
 
     END LOOP;
 
-    -- creating index to speed-up per-date queries, and it speeds up a lot..
-    CREATE INDEX aggr_availability_base_date_idx ON aggr_availability(base_date);
-
     -- logging
     INSERT INTO control (name, start_time, end_time, total)
         VALUES ('loading aggr_availability', start_ts, CLOCK_TIMESTAMP(), total_rows);