Added ChartMetaActions Fucntion for Querying by Truncated Timestamps

give it:
- a chart
- a truncation span ("minutes", "hours", "days", etc)
- (optional) time span
- (optional) bbox

and you get aggregated data for the truncated timestamps

Updates #264

lib/plenario/actions/chart_meta_actions.ex

@@ -55,8 +55,7 @@ defmodule Plenario.Actions.ChartMetaActions do
 
   @template_dir "chart-meta-queries"
 
-  def query_time_bucket!(chart, ts_trunc_interval, ts_trunc_span, ts_range \\ nil, bbox \\ nil)
-  do
+  def query_time_bucket!(chart, ts_trunc_interval, ts_trunc_span, ts_range \\ nil, bbox \\ nil) do
     meta = MetaActions.get(chart.meta_id)
 
     data_fields =
@@ -85,6 +84,34 @@ defmodule Plenario.Actions.ChartMetaActions do
     end
   end
 
+  def query_time_trunc!(chart, ts_trunc_span, ts_range \\ nil, bbox \\ nil) do
+    meta = MetaActions.get(chart.meta_id)
+
+    data_fields =
+      chart.data_fields
+      |> Enum.map(&explode_jsonb_path/1)
+
+    filename = Path.join(:code.priv_dir(:plenario), "#{@template_dir}/date_trunc.sql.eex")
+    sql = EEx.eval_file(filename, [
+      chart: chart,
+      table_name: meta.table_name,
+      ts_range: ts_range,
+      bbox: bbox,
+      data_fields: data_fields,
+      ts_trunc_span: ts_trunc_span,
+    ], trim: true)
+
+    case Ecto.Adapters.SQL.query(Repo, sql) do
+      {:ok, res} ->
+        res
+
+      {:error, error} ->
+        Logger.error(error.postgres.message)
+        Logger.error(sql)
+        raise error
+    end
+  end
+
   defp explode_jsonb_path(path) do
     fields = String.split(path, ".")
     {primary, fields} = List.pop_at(fields, 0)

priv/chart-meta-queries/date_trunc.sql.eex

@@ -0,0 +1,24 @@
+SELECT
+  DATE_TRUNC('<%= ts_trunc_span %>', "<%= chart.timestamp_field %>") AS "<%= chart.timestamp_field %>"
+  <%= for {path, field} <- data_fields do %>
+  , <%= chart.data_agg_func %>((<%= field %>)::numeric)::float AS "<%= path %>"
+  <% end %>
+FROM
+  "<%= table_name %>"
+<%= if ts_range != nil or bbox != nil do %>
+WHERE
+  <%= if ts_range != nil do %>
+  '<%= ts_range %>'::tstzrange @> "<%= chart.timestamp_field %>"
+  <%= if bbox != nil do %>
+  AND
+  <% end %>
+  <% end %>
+  <%= if bbox != nil do %>
+  ST_CONTAINS('<%= bbox %>'::geometry, "<%= chart.location_field %>")
+  <% end %>
+<% end %>
+GROUP BY
+  "<%= chart.timestamp_field %>"
+ORDER BY
+  "<%= chart.timestamp_field %>"
+;

test/plenario/chart_meta_actions_test.exs

@@ -155,4 +155,44 @@ defmodule Plenario.Testing.ChartMetaActionsTest do
       ]
     ]
   end
+
+  test :query_time_trunc!, %{meta: meta, vp: vp} do
+    # insert some more stuff
+    insert = """
+    INSERT INTO "#{meta.table_name}"
+      (node_id, timestamp, longitude, latitude, observations)
+    VALUES
+      ('001', '2018-01-01 00:01:00+00:00', -87.71, 42.1, '{"BMP180": {"temperature": -1.64}, "HTU21D": {"humidity": 71.94, "temperature": -0.78}, "TSYS01": {"temperature": -1.1}}'),
+      ('001', '2018-01-01 00:02:30+00:00', -87.71, 42.1, '{"BMP180": {"temperature": -1.66}, "HTU21D": {"temperature": -0.78}, "TSYS01": {"temperature": -1.1}}'),
+      ('002', '2018-01-01 00:33:00+00:00', -87.72, 42.1, '{"BMP180": {"temperature": -1.65}, "HTU21D": {"humidity": 71.94, "temperature": -0.78}}'),
+      ('003', '2018-01-01 00:04:00+00:00', -87.73, 42.1, '{"BMP180": {"temperature": -1.65}, "HTU21D": {"humidity": 71.94, "temperature": -0.78}, "TSYS01": {"temperature": -1.1}}'),
+      ('004', '2018-01-01 00:25:00+00:00', -87.74, 42.1, '{"BMP180": {"temperature": -1.65}, "HTU21D": {"humidity": 71.94, "temperature": -0.78}, "TSYS01": {"temperature": -1.1}}'),
+      ('005', '2018-01-01 00:16:00+00:00', -87.75, 42.1, '{"bananas": 1}')
+    ;
+    """
+    {:ok, _} = Ecto.Adapters.SQL.query(Repo, insert)
+
+
+    {:ok, cm} = ChartMetaActions.create(
+      meta, "name", "description", "timestamp", vp.name,
+      ["observations.BMP180.temperature"], "avg")
+
+    %Postgrex.Result{columns: cols, rows: rows, num_rows: 8} =
+      ChartMetaActions.query_time_trunc!(cm, "minutes")
+
+    assert cols == [
+      "timestamp", "observations.BMP180.temperature"
+    ]
+
+    assert rows == [
+      [{{2018, 1, 1}, {0, 0, 0, 0}}, -1.66],
+      [{{2018, 1, 1}, {0, 0, 0, 0}}, -1.6475],
+      [{{2018, 1, 1}, {0, 1, 0, 0}}, -1.64],
+      [{{2018, 1, 1}, {0, 2, 0, 0}}, -1.66],
+      [{{2018, 1, 1}, {0, 4, 0, 0}}, -1.65],
+      [{{2018, 1, 1}, {0, 16, 0, 0}}, nil],
+      [{{2018, 1, 1}, {0, 25, 0, 0}}, -1.65],
+      [{{2018, 1, 1}, {0, 33, 0, 0}}, -1.65]
+    ]
+  end
 end