feat: add an aggregated velocity statistics view

alembic/versions/589113bd8e5e_add_materialized_view_siri_agg_velocity_.py

@@ -0,0 +1,57 @@
+"""Add materialized view siri_agg_velocity_stats
+
+Revision ID: 589113bd8e5e
+Revises: eb501cf9f471
+Create Date: 2024-12-16 18:05:19.088109+00:00
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+import open_bus_stride_db
+
+
+# revision identifiers, used by Alembic.
+revision = '589113bd8e5e'
+down_revision = 'eb501cf9f471'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.execute("DROP MATERIALIZED VIEW IF EXISTS siri_agg_velocity_stats")
+    op.execute("""
+        create materialized view siri_agg_velocity_stats as
+        WITH HourlyAverages AS (
+            SELECT
+                trunc(lon * 500 + .5)/500 AS lonRound,
+                trunc(lat * 500 + .5)/500 AS latRound,
+                DATE(recorded_at_time) AS date,
+                DATE_PART('hour', recorded_at_time) AS hour,
+                AVG(velocity) AS hourly_avg,
+                COUNT(1) as sample_number
+            FROM siri_vehicle_location svl
+            WHERE velocity > 0 AND velocity < 200 AND lon > 0 and lat > 0
+            GROUP BY lonRound, latRound, date, hour
+            having COUNT(1) > 5
+        )
+        SELECT
+            lonRound,
+            latRound,
+            date,
+            STDDEV(hourly_avg) AS stddev_hourly_avg,
+            AVG(hourly_avg) AS avg_hourly_avg,
+            SUM(sample_number) as sample_number,
+            PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY hourly_avg) AS median_hourly_avg
+        FROM HourlyAverages
+        GROUP BY lonRound, latRound, date;
+    """)
+    op.execute("create index idx_siri_agg_velocity_stats_lonRound_latRound on siri_agg_velocity_stats (lonRound, latRound)")
+    op.execute("create index idx_siri_agg_velocity_stats_date on siri_agg_velocity_stats (date)")
+    op.execute("REFRESH MATERIALIZED VIEW siri_agg_velocity_stats")
+    # This unique index allows to refresh the materialized view concurrently (it was created manually)
+    op.execute("create unique index siri_agg_velocity_stats_uniq_idx on siri_agg_velocity_stats (lonRound, latRound, date);")
+
+def downgrade():
+    op.execute("drop materialized view if exists siri_agg_velocity_stats")