APP-1086: fix BigQuery nanosecond timestamp cast failure in edr_cast_as_timestamp

[MikaKerman]

Summary

Adds a BigQuery-specific override for edr_cast_as_timestamp that truncates sub-microsecond fractional digits before casting to TIMESTAMP.

BigQuery's TIMESTAMP only supports microsecond precision (6 fractional digits). Some runtimes (e.g. dbt-fusion) write nanosecond-precision strings like 2026-04-03T10:50:50.961498756Z into Elementary's dbt_run_results columns (execute_started_at, execute_completed_at, compile_started_at, compile_completed_at). The default cast(field as timestamp) then fails with Database Error: Invalid timestamp: '...' and blocks edr send-report / edr report until the bad rows age out.

The new bigquery__edr_cast_as_timestamp macro wraps the value in regexp_replace(..., r'(\.\d{6})\d+', r'\1') before the cast, truncating any extra fractional digits to exactly 6. Strings with ≤ 6 fractional digits are unaffected. This follows the same dispatch pattern as the existing dremio__edr_cast_as_timestamp truncation. bigquery__edr_cast_as_date chains through edr_cast_as_timestamp, so the fix applies there transparently as well.

Linear: APP-1086

Review & Testing Checklist for Human

• On a BigQuery target, seed dbt_run_results with at least one row where execute_completed_at has 9 fractional digits (e.g. 2026-04-03T10:50:50.961498756Z) and confirm edr send-report / edr report no longer fails on the days_back filter.
• Confirm existing rows with ≤ 6 fractional digits (or no fractional part) still cast correctly and produce identical results to before this change.
• Run BigQuery integration tests to verify no regression in anomaly detection / monitoring queries that go through edr_cast_as_timestamp.

Notes

• No version bump or release work is included here per the ticket assignee.
• Postgres/Snowflake/Databricks/Spark are unaffected (native nanosecond support or string parsing); Athena/Trino already use try_cast which handles this; Dremio already truncates to millisecond precision.

Link to Devin session: https://app.devin.ai/sessions/3a3eac19b8924571820addc7d6b6a877
Requested by: @MikaKerman

Summary by CodeRabbit

• New Features
  • Improved timestamp precision handling for BigQuery, with enhanced support for truncating sub-microsecond digits before casting to ensure proper data integrity.

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[linear]

APP-1086 Fix BigQuery nanosecond timestamp cast failure in edr_cast_as_timestamp

[github-actions]

👋 @MikaKerman
Thank you for raising your pull request.
Please make sure to add tests and document all user-facing changes.
You can do this by editing the docs files in the elementary repository.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 56ef4698-c008-4fb7-9c6f-f1d47781564e

📥 Commits

Reviewing files that changed from the base of the PR and between 91d04fd and 6b65aa5.

📒 Files selected for processing (1)

• macros/utils/data_types/cast_column.sql

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📝 Walkthrough

Walkthrough

A new BigQuery-specific macro bigquery__edr_cast_as_timestamp is added to truncate sub-microsecond digits from timestamps before casting to the standard timestamp type via string manipulation and regex replacement.

Changes

Timestamp Casting Macro

Layer / File(s)	Summary
BigQuery Timestamp Precision macros/utils/data_types/cast_column.sql	New macro bigquery__edr_cast_as_timestamp(timestamp_field) casts timestamp to string, truncates sub-microsecond precision using regex, and casts back to internal timestamp type to handle BigQuery timestamp precision requirements.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 A macro hops in, swift and clean,
BigQuery timestamps, now pristine!
Sub-microseconds trimmed with care,
Regex magic through the air! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly describes the main change: adding a BigQuery-specific fix for nanosecond timestamp casting in the edr_cast_as_timestamp macro, which is the primary objective of this changeset.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch app-1086-fix-bigquery-nanosecond-timestamp-cast-failure-in

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