On 18.06.2012 21:00, Robert Haas wrote:
On Thu, Jun 14, 2012 at 5:58 PM, Andres Freund<and...@2ndquadrant.com> wrote:
1. Use a 64-bit segment number, instead of the log/seg combination. And
don't waste the last segment on each logical 4 GB log file. The concept
of a "logical log file" is now completely gone. XLogRecPtr is unchanged,
but it should now be understood as a plain 64-bit value, just split into
two 32-bit integers for historical reasons. On disk, this means that
there will be log files ending in FF, those were skipped before.
Whats the reason for keeping that awkward split now? There aren't that many
users of xlogid/xcrecoff and many of those would be better served by using
helper macros.
I wondered that, too. There may be a good reason for keeping it split
up that way, but we at least oughta think about it a bit.
The page header contains an XLogRecPtr (LSN), so if we change it we'll
have to deal with pg_upgrade. I guess we could still keep XLogRecPtr
around as the on-disk representation, and convert between the 64-bit
integer and XLogRecPtr in PageGetLSN/PageSetLSN. I can try that out -
many xlog calculations would admittedly be simpler if it was an uint64.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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