Bq timestamp schema conversion #36986

claudevdm · 2025-12-03T22:14:22Z

Adds ability to map BQ TIMESTAMP(12) columns to either Timestamp.MILLIS, Timestamp.MICROS, Timestamp.NANOS or string for picosecond precision. This is used in the direct read path where a user specifies the precision of the timestamp that the read API returns. E.g. if a user reads with nanosecond precision, TIMESTAMP(12) columns will be mapped to beam LogicalTypes.Timestamp.NANOS etc.
Adds conversion from BQ TableRow timestamps (formatted as UTC strings) to beam rows (where timestamp is a Timestamp logical type

Note: A TimestampPrecision.java enum is added because it will be reused for future PR's (e.g. specifying the desired read precision).

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gemini-code-assist · 2025-12-03T22:14:41Z

Summary of Changes

Hello @claudevdm, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances Apache Beam's integration with BigQuery by providing more granular control over how high-precision timestamp data is handled. It allows users to define the desired precision when converting BigQuery's TIMESTAMP(12) columns into Beam's schema types, ensuring data integrity and flexibility for applications requiring specific timestamp resolutions. The changes also refine the internal mechanisms for parsing and formatting timestamp values between BigQuery and Beam's data models.

Highlights

BigQuery TIMESTAMP(12) Mapping: Adds the capability to map BigQuery TIMESTAMP(12) columns, which offer picosecond precision, to various Beam logical timestamp types: Timestamp.MILLIS, Timestamp.MICROS, Timestamp.NANOS, or as a STRING type to preserve full precision.
Timestamp Conversion: Introduces improved conversion logic for timestamps, allowing BigQuery TableRow timestamps (formatted as UTC strings) to be accurately mapped to Beam rows with the appropriate Timestamp logical type.
Configurable Precision: A new TimestampPrecision enum and a picosecondTimestampMapping option have been added to BigQueryUtils.SchemaConversionOptions, enabling users to specify the desired precision for TIMESTAMP(12) columns, defaulting to nanoseconds.
Variable Precision Formatter: A new VAR_PRECISION_FORMATTER is introduced to handle parsing of timestamp strings with varying numbers of decimal places for nanoseconds, ensuring robust conversion from BigQuery string representations to Java Instant objects.

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claudevdm · 2025-12-03T22:16:01Z

/gemini review

gemini-code-assist

Code Review

This pull request introduces the ability to map BigQuery TIMESTAMP(12) columns to various Beam timestamp precisions or to a string, which is a valuable enhancement for handling high-precision timestamps. The changes also include converting BigQuery TableRow timestamps to Beam rows. The implementation is solid and is accompanied by a good set of tests.

I have a couple of minor suggestions:

In BigQueryUtils.java, there's an opportunity to make a Long comparison more robust.
In TimestampPrecision.java, there's a small typo in the Javadoc.

Overall, this is a great contribution.

...o/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigquery/BigQueryUtils.java

...gle-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigquery/TimestampPrecision.java

claudevdm · 2025-12-03T22:24:51Z

R: @Abacn

claudevdm · 2025-12-03T22:24:57Z

R: @ahmedabu98

github-actions · 2025-12-03T22:25:56Z

Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control. If you'd like to restart, comment assign set of reviewers

github-actions · 2025-12-03T22:26:02Z

Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control. If you'd like to restart, comment assign set of reviewers

Abacn · 2025-12-05T21:32:12Z

...o/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigquery/BigQueryUtils.java

-        return FieldType.DATETIME;
+        // Timestamp columns can only have 6 or 12 precision.
+        if ((schema.getTimestampPrecision() == null)
+            || Long.valueOf(6L).equals(schema.getTimestampPrecision())) {


I saw a test "testFromTableSchema_timestampNullPrecision_defaultsToDatetime" noted that null getTimestampPrecision was for backward compatibility. Is this also the case for schema.getTimestampPrecision() == 6? Sounds confusing anyways (FieldType.DATETIME only has millis precision)

Any chance to maintain maximum compatibility while respect schema.getTimestampPrecision (e.g. upgrade_compatibility flag etc)?

Abacn · 2025-12-05T21:42:49Z

...o/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigquery/BigQueryUtils.java

   * @param nestedFields Nested fields for the given type (eg. RECORD type)
   * @return Corresponding Beam {@link FieldType}
   */
  private static FieldType fromTableFieldSchemaType(


We now pass the whole TableFieldSchema. It also contains nestedFields (schema.getFields()). To avoid potential mixed use of two sources of nestedFields, either remove the second parameter, or add a overload method fromTableFieldSchemaType(TableFieldSchema schema, SchemaConversionOptions options)

Abacn · 2025-12-05T21:46:03Z

...gle-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigquery/TimestampPrecision.java

+package org.apache.beam.sdk.io.gcp.bigquery;
+
+/** Specifies Timestamp precision. */
+public enum TimestampPrecision {


Consider point to BigQuery API's TableFieldSchema.getTimestampPrecision documentation

claudevdm and others added 3 commits December 3, 2025 21:16

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github-actions bot added java io gcp labels Dec 3, 2025

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...gle-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigquery/TimestampPrecision.java Outdated Show resolved Hide resolved

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Bq timestamp schema conversion #36986

Bq timestamp schema conversion #36986

claudevdm commented Dec 3, 2025 •

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claudevdm commented Dec 3, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Note: A TimestampPrecision.java enum is added because it will be reused for future PR's (e.g. specifying the desired read precision).

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claudevdm commented Dec 3, 2025 •

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