Add test suite for IPC:ParallelFinish hang reproduction #1
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Adds comprehensive test suite to reproduce Theory 1 (shared memory queue saturation) for the recurring IPC:ParallelFinish hang issue. Test files: - test_parallel_queue_saturation.sql: Main reproduction test with 250K dead tuples and flood_error_queue() function to saturate 16KB error queues - monitor_parallel_hang.sql: Monitoring script to observe wait events - test_parallel_hang_alternative.sql: 7 alternative test approaches - run_reproduction_test.sh: Automated setup and execution script - test_parallel_hang_README.md: Complete documentation Theory being tested: Workers block indefinitely when error queues fill up, creating circular dependency where workers need leader to drain queue but leader only drains when ParallelMessagePending flag is set, which requires successful worker message send (impossible when queue full). Note: Tests target PostgreSQL 16.3 specifically per production environment.
Analyzes two critical commits merged after PostgreSQL 16.3: - 6f6521d (16.4): Don't enter parallel mode when holding interrupts - 06424e9 (16.5): Improved fix for interrupt handling These commits directly address the IPC:ParallelFinish hang issue by preventing parallel worker launch when leader cannot process interrupts, which eliminates the deadlock scenario where workers block on full error queues while leader cannot drain them. Recommendation: Upgrade to PostgreSQL 16.5+ to resolve production issue.
NikolayS
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Dec 23, 2025
truncate_useless_pathkeys() seems to have neglected to account for PathKeys that might be useful for WindowClause evaluation. Modify it so that it properly accounts for that. Making this work required adjusting two things: 1. Change from checking query_pathkeys to check sort_pathkeys instead. 2. Add explicit check for window_pathkeys For #1, query_pathkeys gets set in standard_qp_callback() according to the sort order requirements for the first operation to be applied after the join planner is finished, so this changes depending on which upper planner operations a particular query needs. If the query has window functions and no GROUP BY, then query_pathkeys gets set to window_pathkeys. Before this change, this meant PathKeys useful for the ORDER BY were not accounted for in queries with window functions. Because of #1, #2 is now required so that we explicitly check to ensure we don't truncate away PathKeys useful for window functions. Author: David Rowley <dgrowleyml@gmail.com> Discussion: https://postgr.es/m/CAApHDvrj3HTKmXoLMbUjTO=_MNMxM=cnuCSyBKidAVibmYPnrg@mail.gmail.com
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Adds comprehensive test suite to reproduce Theory 1 (shared memory queue saturation) for the recurring IPC:ParallelFinish hang issue.
Test files:
Theory being tested: Workers block indefinitely when error queues fill up, creating circular dependency where workers need leader to drain queue but leader only drains when ParallelMessagePending flag is set, which requires successful worker message send (impossible when queue full).
Note: Tests target PostgreSQL 16.3 specifically per production environment.