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That is so new to me. So > 1. if log wrap around happens and some Wal-Files containing uncomitted l= og records are being overwritten, No, they are deleted (well, perhaps recycled, but that amounts to the same)= . > 2. AND iin the mean time some data updates pertaining to these uncomitte= d transactions have been flushed from the data buffers to disk > 3. AND after the data buffers have been flushed the transaction fails ( a= nd I assume releases all the locks )=20 >=20 > how does postgres know that a particular unlocked row it finds in the di= sk ( or even the bufferpool > for that matter ) is not in a valid state even though it physically exis= ts in the table? > How can it decode this information?