On 04/13/14 08:27, Marko Kreen wrote:
On Sat, Apr 12, 2014 at 02:10:13PM -0400, Jan Wieck wrote:
Since it doesn't seem to produce any side effects, I'd think that
making the snapshot unique within txid_current_snapshot() and
filtering duplicates on input should be sufficient and eligible for
backpatching.
Agreed.
The attached patch adds a unique loop to the internal
sort_snapshot() function and skips duplicates on input. The git
commit is here:
https://github.com/wieck/postgres/commit/a88a2b2c25b856478d7e2b012fc718106338fe00
static void
sort_snapshot(TxidSnapshot *snap)
{
+ txid last = 0;
+ int nxip, idx1, idx2;
+
if (snap->nxip > 1)
+ {
qsort(snap->xip, snap->nxip, sizeof(txid), cmp_txid);
+ nxip = snap->nxip;
+ idx1 = idx2 = 0;
+ while (idx1 < nxip)
+ {
+ if (snap->xip[idx1] != last)
+ last = snap->xip[idx2++] = snap->xip[idx1];
+ else
+ snap->nxip--;
+ idx1++;
+ }
+ }
}
I think you need to do SET_VARSIZE also here. Alternative is to
move SET_VARSIZE after sort_snapshot().
And it seems the drop-double-txid logic should be added also to
txid_snapshot_recv(). It seems weird to have it behave differently
from txid_snapshot_in().
Thanks,
yes on both issues. Will create another patch.
Jan
--
Jan Wieck
Senior Software Engineer
http://slony.info
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