On 22 August 2015 at 15:14, Andres Freund <and...@anarazel.de> wrote:
> TransactionIdSetPageStatus() calls TransactionIdSetStatusBit(), which > writes an 8 byte variable (the lsn). That's not safe. > This point was the main sticking point here. It turns out that we don't need to store the LSN (8 bytes). WAL is fsynced every time we finish writing a file, so we only actually need to store the byte position within each file, so no more than 16MB. That fits within a 4 byte value, so can be written atomically. So I have a valid way forward for this approach. Cool. -- Simon Riggs http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
