Troubleshooting CockroachDB Test Failure TestCCLLogic_fk_read_committed

by Sharif Sakr 72 views

It appears that the TestCCLLogic_fk_read_committed test within CockroachDB's pkg/ccl/logictestccl/tests/fakedist-vec-off/fakedist-vec-off_test package has failed on the release-25.2.3-rc branch. This failure occurred at commit adfe5601ff6cb72c0f65090995978ca9ebbdc647. Let's dive into the details, understand the potential causes, and explore how to address this issue.

Decoding the Error Log

First, let's break down the provided error log. The stack trace points to a series of function calls within CockroachDB's SQL execution engine. Key areas to focus on include:

  • pkg/sql/rowexec.(*noopProcessor).Next: This suggests an issue during row processing, possibly an unexpected state or error while iterating through results.
  • pkg/sql.(*rowSourceToPlanNode).Next: Indicates a problem in converting a row source (the data source) to a plan node (part of the execution plan).
  • pkg/sql.(*updateNode).BatchedNext: Points to a failure during an UPDATE operation, specifically when processing updates in batches.
  • pkg/sql.(*rowCountNode).startExec: This implicates the row count node, which is responsible for tracking the number of rows affected by a statement.
  • pkg/sql.(*DistSQLPlanner).Run and pkg/sql.(*DistSQLPlanner).PlanAndRun: These methods are part of the distributed SQL execution engine, suggesting the issue might be related to how the query is planned and executed across multiple nodes.
  • pkg/sql.(*connExecutor).execStmt: This is the connection executor, which handles the execution of SQL statements. Errors here can stem from various issues during the statement lifecycle.

Keywords: CockroachDB, TestCCLLogic_fk_read_committed, SQL execution engine, distributed SQL execution, error log analysis

Potential Root Causes

Based on the stack trace, several potential root causes could be at play. To effectively troubleshoot, it's important to consider these possibilities and narrow them down through further investigation:

  1. Foreign Key Constraint Violation: The test name fk_read_committed strongly suggests that foreign key constraints are involved. A violation of these constraints, such as attempting to insert a row with a foreign key that doesn't exist in the referenced table, could lead to this failure. The read-committed isolation level guarantees that a transaction only sees committed data, so if a concurrent transaction modifies the referenced table, it could lead to inconsistencies.
  2. Concurrency Issues: CockroachDB is a distributed database, and concurrency is a key consideration. Race conditions or deadlocks during concurrent transactions, particularly those involving foreign key relationships, could trigger this error. The stack trace's mention of distributed planning and execution reinforces this possibility.
  3. Data Inconsistency: The fakedist-vec-off part of the test path suggests that this test is designed to simulate a distributed environment with certain features disabled (likely vectorized execution). This might expose edge cases related to data consistency across nodes. If data is not properly synchronized or if there are inconsistencies in the data seen by different nodes, foreign key checks could fail.
  4. Bug in Distributed Query Planning: The distributed SQL planner is responsible for optimizing and distributing queries across the cluster. A bug in the planner could lead to an incorrect execution plan that violates foreign key constraints or introduces other errors. The stack trace points to the planner, making this a plausible cause.
  5. Serialization Errors: When data is moved between different parts of the system, it needs to be serialized and deserialized. Errors during these processes can lead to data corruption or incorrect state, potentially triggering foreign key violations.

Keywords: Foreign Key Constraint, Concurrency Issues, Data Inconsistency, Distributed Query Planning, Serialization Errors

Steps to Investigate and Resolve the Failure

To effectively resolve this TestCCLLogic_fk_read_committed failure, a systematic approach is required. Here's a breakdown of the steps:

  1. Reproduce the Failure Locally: The first step is to try and reproduce the failure in a local development environment. This allows for easier debugging and experimentation. Use the provided commit hash (adfe5601ff6cb72c0f65090995978ca9ebbdc647) to check out the specific version of CockroachDB and run the test (pkg/ccl/logictestccl/tests/fakedist-vec-off/fakedist-vec-off_test.TestCCLLogic_fk_read_committed).
  2. Examine the Test Logic: Carefully review the test code to understand the specific SQL operations being performed, the data being inserted, and the foreign key relationships involved. Pay close attention to any concurrency-related aspects of the test. Understanding the test's intent is crucial for identifying the root cause.
  3. Analyze the SQL Logs: Enable detailed SQL logging to capture the exact SQL statements being executed by the test. This can provide valuable insights into the sequence of operations and any potential errors occurring at the SQL level. Look for any unusual query plans or unexpected behavior.
  4. Use Debugging Tools: Utilize Go's debugging tools (e.g., Delve) to step through the code and inspect the state of variables at different points in the execution. This can help pinpoint the exact location where the failure occurs and identify the underlying cause. Focus on the areas highlighted in the stack trace, such as the updateNode and the distributed SQL planner.
  5. Inspect Data: Inspecting the data involved in the test, both before and after the failing operation, can reveal inconsistencies or unexpected values that might be triggering the failure. This is especially important when dealing with foreign key constraints.
  6. Simplify the Test Case: If the test case is complex, try to simplify it by removing unnecessary operations or data. This can help isolate the specific scenario that's causing the failure and make it easier to debug.
  7. Consider Recent Changes: Review the recent changes made to the code in the areas highlighted by the stack trace, particularly those related to foreign key constraints, distributed query planning, and concurrency control. It's possible that a recent change introduced a bug that's causing the failure.
  8. Consult CockroachDB Community and Resources: If you're still stuck, reach out to the CockroachDB community for help. The CockroachDB forums, Slack channel, and GitHub issues are excellent resources for getting assistance from experienced developers and users. Share the error log, your investigation steps, and any relevant code snippets to get the most effective help.

Keywords: Reproduce Failure Locally, Examine Test Logic, Analyze SQL Logs, Use Debugging Tools, Inspect Data, Simplify Test Case, Consider Recent Changes, CockroachDB Community

Focus on Foreign Key Constraints and Read Committed Isolation

Given the test name and the potential causes discussed earlier, it's highly likely that the issue is related to the interaction between foreign key constraints and the read-committed isolation level. Here's a deeper dive into these concepts:

  • Foreign Key Constraints: These constraints enforce referential integrity between tables. They ensure that relationships between data in different tables are maintained. When a row is inserted or updated in a table with a foreign key, the database checks if the corresponding value exists in the referenced table. If not, the operation fails. This mechanism is crucial for data consistency.
  • Read Committed Isolation: This is a common transaction isolation level in databases. It guarantees that a transaction only sees committed data from other transactions. This prevents