fix: truncate nanosecond-precision timestamps for BigQuery before casting

[devin-ai-integration]

Summary

Adds a bigquery__edr_cast_as_timestamp dispatch macro that truncates fractional seconds beyond microsecond precision (6 digits) before casting string values to TIMESTAMP.

Problem: Starting with dbt-bigquery >= 1.11, nanosecond-precision timestamps (9 fractional digits, e.g. 2026-04-03T10:50:50.961498756Z) began appearing in string columns like execute_completed_at in dbt_run_results. BigQuery's TIMESTAMP type only supports microsecond precision (6 digits), so CAST(... AS TIMESTAMP) fails with Invalid timestamp errors — completely blocking edr report and edr send-report. Reported by multiple users in the community Slack.

Fix: Uses regexp_replace to truncate to 6 fractional digits before casting, following the same pattern as the existing Dremio override. Timestamps with ≤6 fractional digits or no fractional seconds pass through unchanged. The existing bigquery__edr_cast_as_date macro already calls edr_cast_as_timestamp internally, so it also benefits.

Review & Testing Checklist for Human

• Verify BigQuery regex syntax: confirm r'(\.\d{6})\d+' with '\\1' backreference is valid BigQuery REGEXP_REPLACE usage
• Test against a real BigQuery instance with nanosecond-precision timestamps in dbt_run_results — CI likely does not cover BigQuery-specific behavior
• Verify edge cases: timestamps with exactly 6 fractional digits, no fractional seconds, and NULL values should all cast correctly without errors

Recommended test plan: Run edr report or edr send-report against a BigQuery project that has nanosecond-precision timestamps in the dbt_run_results table (or manually insert a row with e.g. 2026-04-03T10:50:50.961498756Z in execute_completed_at) and confirm the report generates successfully.

Notes

• This only affects BigQuery; all other adapters continue using the default cast(... as timestamp) path
• The regex is a no-op for timestamps that already have ≤6 fractional digits, so there is no behavioral change for well-formed data

Link to Devin session: https://app.devin.ai/sessions/8841375f9b774c8088e1bff6c8e44f52
Requested by: @MikaKerman

Summary by CodeRabbit

• Bug Fixes
  • Resolved timestamp casting issues for BigQuery when handling high-precision values with fractional seconds, ensuring accurate data type conversions.

[devin-ai-integration]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 33843bd0-d2f7-4df9-909a-2fc8ff7f9037

📥 Commits

Reviewing files that changed from the base of the PR and between 9f32d47 and 760e97a.

📒 Files selected for processing (1)

• macros/utils/data_types/cast_column.sql

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📝 Walkthrough

Walkthrough

A BigQuery-specific macro override is added to cast_column.sql that handles timestamp casting by converting to string, truncating fractional seconds to 6 digits using regex, and casting to the elementary timestamp type.

Changes

Cohort / File(s)	Summary
BigQuery Timestamp Casting macros/utils/data_types/cast_column.sql	Added bigquery__edr_cast_as_timestamp macro that converts timestamps to strings, truncates fractional seconds to 6 digits via regexp_replace, and casts to the appropriate type.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 In BigQuery's grand temporal halls,
A macro hops through fractional walls,
Six digits we keep, the rest we discard,
Truncating precision—no task is too hard!
Timestamps now dance in elastic delight. ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding a BigQuery-specific macro that truncates nanosecond-precision timestamps before casting. It directly reflects the core fix in the changeset.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch devin/1776323745-fix-bigquery-nanosecond-timestamp

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