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CE amcheck: fix multiple problems with TOAST pointer validation · postgrespro/postgres@ec7ffb8 · GitHub
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robertmhaasrobertmhaas
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amcheck: fix multiple problems with TOAST pointer validation
First, don't perform database access while holding a buffer lock. When checking a heap, we can validate that TOAST pointers are sane by performing a scan on the TOAST index and looking up the chunks that correspond to each value ID that appears in a TOAST poiner in the main table. But, to do that while holding a buffer lock at least risks causing other backends to wait uninterruptibly, and probably can cause undetected and uninterruptible deadlocks. So, instead, make a list of checks to perform while holding the lock, and then perform the checks after releasing it. Second, adjust things so that we don't try to follow TOAST pointers for tuples that are already eligible to be pruned. The TOAST tuples become eligible for pruning at the same time that the main tuple does, so trying to check them may lead to spurious reports of corruption, as observed in the buildfarm. The necessary infrastructure to decide whether or not the tuple being checked is prunable was added by commit 3b6c125, but it wasn't actually used for its intended purpose prior to this patch. Mark Dilger, adjusted by me to avoid a memory leak. Discussion: http://postgr.es/m/AC5479E4-6321-473D-AC92-5EC36299FBC2@enterprisedb.com
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