Fix VLE queries failing on read-only replicas (#2160)#2345
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jrgemignani merged 1 commit intoapache:masterfrom Feb 27, 2026
Merged
Fix VLE queries failing on read-only replicas (#2160)#2345jrgemignani merged 1 commit intoapache:masterfrom
jrgemignani merged 1 commit intoapache:masterfrom
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@gregfelice Again, ty! Three things -
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apologies - fixing
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The global graph cache used by VLE acquired ShareLock when scanning vertex and edge label tables to populate in-memory hashtables. On read-only replicas (standby servers in recovery), PostgreSQL only allows RowExclusiveLock or less, so VLE queries would fail with: "cannot acquire lock mode ShareLock on database objects while recovery is in progress" Change all three functions in age_global_graph.c to use AccessShareLock instead, which is sufficient for read-only table scans and is consistent with the existing ag_cache.c code that performs identical operations. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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@jrgemignani Thanks for the review! Rebased onto master (on top of the merged VLE PR) and retarget the PR base branch. AI (Claude, Anthropic) was used to assist in developing this fix. |
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Looks like I have to close and reopen the PR to get the CI to run. Don't panic! |
jrgemignani
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Feb 27, 2026
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Summary
Fixes #2160.
VLE queries fail on read-only replicas (standby servers) with:
Root Cause
The VLE global graph cache (
age_global_graph.c) acquiresShareLockwhen scanning vertex and edge label tables to populate in-memory hashtables. On standby servers in recovery mode, PostgreSQL restricts locks toRowExclusiveLockor lower.ShareLockexceeds this threshold.The three affected functions are:
get_ag_labels_names()— scansag_labelcatalog tableload_vertex_hashtable()— scans vertex label tablesload_edge_hashtable()— scans edge label tablesAll three perform read-only sequential scans to populate caches — no writes.
Fix
Change
ShareLocktoAccessShareLockin all three functions (6 call sites: 3table_open+ 3table_close).AccessShareLockis:ag_cache.ccode, which performs identical catalog scan operations usingAccessShareLock(18 call sites)Test Plan