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In VACUUM FULL, an interrupt after the initial transaction has been recorded as committed can cause postmaster to restart with the following error message: PANIC: cannot abort transaction NNNN, it was already committed This problem has been reported many times. In lazy VACUUM, an interrupt after the table has been truncated by lazy_truncate_heap causes other backends' relcache to still point to the removed pages; this can cause future INSERT and UPDATE queries to error out with the following error message: could not read block XX of relation 1663/NNN/MMMM: read only 0 of 8192 bytes The window to this race condition is extremely narrow, but it has been seen in the wild involving a cancelled autovacuum process. The solution for both problems is to inhibit interrupts in both operations until after the respective transactions have been committed. It's not a complete solution, because the transaction could theoretically be aborted by some other error, but at least fixes the most common causes of both problems.