Reapply "Have Glean stable views parse datetime metrics as timestamps (bug 1771733) (#3343)" (#3453)

This reverts commit c43bb6c608.

sql/mozfun/glean/parse_datetime/metadata.yaml

@@ -0,0 +1,6 @@
+---
+description: |
+  Parses a Glean datetime metric string value as a BigQuery timestamp.
+
+  See https://mozilla.github.io/glean/book/reference/metrics/datetime.html
+friendly_name: Parse Datetime

sql/mozfun/glean/parse_datetime/udf.sql

@@ -0,0 +1,30 @@
+CREATE OR REPLACE FUNCTION glean.parse_datetime(datetime_string STRING)
+RETURNS TIMESTAMP AS (
+  COALESCE(
+    SAFE.PARSE_TIMESTAMP('%FT%H:%M:%E*S%Ez', datetime_string),
+    SAFE.PARSE_TIMESTAMP('%FT%H:%M%Ez', datetime_string),
+    SAFE.PARSE_TIMESTAMP('%FT%H%Ez', datetime_string),
+    SAFE.PARSE_TIMESTAMP('%F%Ez', datetime_string)
+  )
+);
+
+-- Tests
+SELECT
+  assert.equals(
+    TIMESTAMP '2000-01-02 03:04:05.123456',
+    glean.parse_datetime('2000-01-02T03:04:05.123456789+00:00')
+  ),
+  assert.equals(
+    TIMESTAMP '2000-01-02 03:04:05.123456',
+    glean.parse_datetime('2000-01-02T03:04:05.123456+00:00')
+  ),
+  assert.equals(
+    TIMESTAMP '2000-01-02 03:04:05.123',
+    glean.parse_datetime('2000-01-02T03:04:05.123+00:00')
+  ),
+  assert.equals(TIMESTAMP '2000-01-02 03:04:05', glean.parse_datetime('2000-01-02T03:04:05+00:00')),
+  assert.equals(TIMESTAMP '2000-01-02 09:04:05', glean.parse_datetime('2000-01-02T03:04:05-06:00')),
+  assert.equals(TIMESTAMP '2000-01-02 03:04:00', glean.parse_datetime('2000-01-02T03:04+00:00')),
+  assert.equals(TIMESTAMP '2000-01-02 03:00:00', glean.parse_datetime('2000-01-02T03+00:00')),
+  assert.equals(TIMESTAMP '2000-01-02 00:00:00', glean.parse_datetime('2000-01-02+00:00')),
+  assert.null(glean.parse_datetime('2000-01-02 00:00:00 Z'))

sql_generators/stable_views/__init__.py

@@ -139,11 +139,34 @@ def write_view_if_not_exists(target_project: str, sql_dir: Path, schema: SchemaF
             and schema.bq_table == "metrics_v1"
         ):
             # todo: use mozfun udfs
-            replacements += [
+            metrics_source = (
                 "mozdata.udf.normalize_fenix_metrics"
                 "(client_info.telemetry_sdk_build, metrics)"
-                " AS metrics"
+            )
+        else:
+            metrics_source = "metrics"
+        if metrics_datetime_fields := [
+            metrics_datetime_field["name"]
+            for field in schema.schema
+            if field["name"] == "metrics"
+            for metrics_field in field["fields"]
+            if metrics_field["name"] == "datetime"
+            for metrics_datetime_field in metrics_field["fields"]
+        ]:
+            replacements += [
+                f"(SELECT AS STRUCT {metrics_source}.* REPLACE (STRUCT("
+                + ", ".join(
+                    field_select
+                    for field in metrics_datetime_fields
+                    for field_select in (
+                        f"mozfun.glean.parse_datetime(metrics.datetime.{field}) AS {field}",
+                        f"metrics.datetime.{field} AS raw_{field}",
+                    )
+                )
+                + ") AS datetime)) AS metrics"
             ]
+        elif metrics_source != "metrics":
+            replacements += [f"{metrics_source} AS metrics"]
         if schema.bq_dataset_family == "firefox_desktop":
             # FOG does not provide an app_name, so we inject the one that
             # people already associate with desktop Firefox per bug 1672191.