4 Byte PK support by sm745052 · Pull Request #4010 · GoogleCloudPlatform/DataflowTemplates

sm745052 · 2026-07-10T05:55:17Z

No description provided.

gemini-code-assist · 2026-07-10T05:55:27Z

Summary of Changes

Hello, 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 introduces support for 4-byte character sets (such as emojis) in primary keys during source database to Spanner migrations. The changes involve refining the collation order logic for both MySQL and PostgreSQL to ensure these characters are correctly processed and validated, alongside new integration tests to validate the end-to-end migration flow.

Highlights

4-Byte Character Support: Updated SQL collation queries for MySQL and PostgreSQL to correctly handle 4-byte UTF-8 characters (like emojis) in primary keys.
Integration Testing: Added new integration tests for both MySQL and PostgreSQL to verify the migration of tables containing 4-byte string primary keys.

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gemini-code-assist

Code Review

This pull request updates the collation order queries for MySQL and PostgreSQL to support 4-byte UTF-8 characters and adds corresponding integration tests. Feedback highlights a significant performance concern in the MySQL query due to the massive increase in rows (to over 1.1 million) processed during 4-byte codepoint generation, which could cause high CPU/IO load and disk sorting. Additionally, the new integration tests should be refactored to use instance fields instead of static fields for resource managers and to declare the Dataflow job info as a local variable.

gemini-code-assist · 2026-07-10T05:58:40Z

+  'WHERE t1.h BETWEEN ''00'' AND ''7f'''
 );

+SET @all_utf8_hex = CONCAT(@four_byte_codepoints, ' UNION ALL ', @three_byte_codepoints, ' UNION ALL ', @two_byte_codepoints, ' UNION ALL ', @one_byte_codepoints);


Performance Concern: Scale of 4-Byte Codepoints

Including 4-byte codepoints increases the number of rows processed by this query from ~65,000 (for 1, 2, and 3-byte characters) to over 1.1 million (a ~17x increase).

Since the query performs 6 FIRST_VALUE and 2 DENSE_RANK window functions, MySQL will have to perform multiple large-scale sorts. With 1.1 million rows, this is highly likely to exceed the default MySQL sort_buffer_size (typically 256KB) and tmp_table_size, forcing MySQL to write large temporary files to disk.

This can cause:

Significant CPU and I/O load on the source database during pipeline initialization.

Query execution time to increase from < 60 seconds to several minutes, potentially causing timeouts.

Recommendations:

Benchmark this query on a standard MySQL instance with default configuration to measure the performance impact.

Consider if we can optimize the 4-byte range or if we can increase the session-level sort_buffer_size and join_buffer_size before running this query (e.g., SET SESSION sort_buffer_size = ...).

gemini-code-assist · 2026-07-10T05:58:40Z

+import org.apache.beam.it.gcp.spanner.SpannerResourceManager;
+import org.apache.beam.it.gcp.spanner.matchers.SpannerAsserts;
+import org.apache.beam.it.jdbc.JDBCResourceManager;
+import org.apache.beam.it.jdbc.MySQLResourceManager;


The jobInfo field is only used within the testMySqlToSpanner method and does not need to be a class field. Additionally, the resource managers do not need to be static since they are initialized in the non-static @Before method. Making them instance fields prevents potential issues if tests are run in parallel or if multiple test methods are added in the future.

Suggested change

import org.apache.beam.it.gcp.spanner.SpannerResourceManager;

import org.apache.beam.it.gcp.spanner.matchers.SpannerAsserts;

import org.apache.beam.it.jdbc.JDBCResourceManager;

import org.apache.beam.it.jdbc.MySQLResourceManager;

private MySQLResourceManager mySQLResourceManager;

private SpannerResourceManager spannerResourceManager;

gemini-code-assist · 2026-07-10T05:58:40Z

+    spannerResourceManager = setUpSpannerResourceManager();
+  }


Declare jobInfo as a local variable since it is only used within this test method.

Suggested change

spannerResourceManager = setUpSpannerResourceManager();

}

PipelineLauncher.LaunchInfo jobInfo =

launchDataflowJob(

gemini-code-assist · 2026-07-10T05:58:40Z

+import org.apache.beam.it.gcp.spanner.SpannerResourceManager;
+import org.apache.beam.it.gcp.spanner.matchers.SpannerAsserts;
+import org.apache.beam.it.jdbc.JDBCResourceManager;
+import org.apache.beam.it.jdbc.PostgresResourceManager;


The jobInfo field is only used within the testPostgreSQLToSpanner method and does not need to be a class field. Additionally, the resource managers do not need to be static since they are initialized in the non-static @Before method. Making them instance fields prevents potential issues if tests are run in parallel or if multiple test methods are added in the future.

Suggested change

import org.apache.beam.it.gcp.spanner.SpannerResourceManager;

import org.apache.beam.it.gcp.spanner.matchers.SpannerAsserts;

import org.apache.beam.it.jdbc.JDBCResourceManager;

import org.apache.beam.it.jdbc.PostgresResourceManager;

private PostgresResourceManager postgreSQLResourceManager;

private SpannerResourceManager spannerResourceManager;

gemini-code-assist · 2026-07-10T05:58:40Z

+    spannerResourceManager = setUpSpannerResourceManager();
+  }


Declare jobInfo as a local variable since it is only used within this test method.

Suggested change

spannerResourceManager = setUpSpannerResourceManager();

}

PipelineLauncher.LaunchInfo jobInfo =

launchDataflowJob(

codecov · 2026-07-10T06:09:02Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 63.48%. Comparing base (3f0e4bb) to head (0fcc113).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #4010      +/-   ##
============================================
+ Coverage     55.69%   63.48%   +7.78%     
+ Complexity     6772     2498    -4274     
============================================
  Files          1125      536     -589     
  Lines         68437    30710   -37727     
  Branches       7719     3418    -4301     
============================================
- Hits          38118    19497   -18621     
+ Misses        27843    10200   -17643     
+ Partials       2476     1013    -1463

Components	Coverage Δ
spanner-templates	`88.08% <ø> (+0.40%)`	⬆️
spanner-import-export	`∅ <ø> (∅)`
spanner-live-forward-migration	`89.19% <ø> (-0.10%)`	⬇️
spanner-live-reverse-replication	`83.39% <ø> (-0.08%)`	⬇️
spanner-bulk-migration	`92.44% <ø> (-0.06%)`	⬇️
gcs-spanner-dv	`89.96% <ø> (+1.41%)`	⬆️
see 613 files with indirect coverage changes

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
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sm745052 requested a review from a team as a code owner July 10, 2026 05:55

sm745052 requested review from dhwanilpatel and manitgupta July 10, 2026 05:55

pull-request-size Bot added the size/L label Jul 10, 2026

sm745052 marked this pull request as draft July 10, 2026 05:55

initial 4 byte supoty with ITs

0fcc113

sm745052 force-pushed the 4b_support branch from e4de4aa to 0fcc113 Compare July 10, 2026 05:56

gemini-code-assist Bot reviewed Jul 10, 2026

View reviewed changes

sm745052 added 5 commits July 10, 2026 07:05

upadte

05c93b6

upadte

ef8ba60

upadte

da70af0

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d0fe3fb

sm745052 force-pushed the 4b_support branch 8 times, most recently from 88454e5 to 5c85c66 Compare July 10, 2026 07:44

upadte

d5e4e86

sm745052 force-pushed the 4b_support branch from 5c85c66 to d5e4e86 Compare July 10, 2026 07:52

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4 Byte PK support#4010

4 Byte PK support#4010
sm745052 wants to merge 7 commits into
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4b_support

sm745052 commented Jul 10, 2026

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-    spannerResourceManager = setUpSpannerResourceManager();
-  }
+    PipelineLauncher.LaunchInfo jobInfo =
+        launchDataflowJob(

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sm745052 commented Jul 10, 2026

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gemini-code-assist Bot commented Jul 10, 2026

Summary of Changes

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Code Review

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Performance Concern: Scale of 4-Byte Codepoints

Recommendations:

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codecov Bot commented Jul 10, 2026

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