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fix: deadlock in table lock #16632
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fix: deadlock in table lock #16632
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zhyass
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fixsplit parse and plan
fix: table locked if max_running_queries = 1
Oct 17, 2024
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fix: table locked if max_running_queries = 1
fix: deadlock in table lock
Oct 20, 2024
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I hereby agree to the terms of the CLA available at: https://docs.databend.com/dev/policies/cla/
Summary
Problem Overview
This PR addresses a deadlock issue that occurs when
max_running_queries
is set to 1 in Databend, resulting in errors like "table locked by other session." The root cause of the deadlock is the inconsistent timing of acquiring table locks during query execution, which leads to conflicts in acquiring the necessary locks.Root Cause
The deadlock happens because queries acquire table locks at different stages of query processing:
This inconsistency creates a situation where:
Conditions That Trigger the Issue
max_running_queries
setting is set to 1.Solution
To resolve the deadlock, this PR introduces a new lock acquisition strategy for queries that need require a table lock(merge into, recluster, update, delete, compact, truncate, replace, ..):
This change ensures a more consistent and deadlock-free process of table lock acquisition across different types of queries.
Impact of the Fix
Tests
Type of change
This change is