On 2015-05-12 06:06, Craig Ringer wrote:
On 11 May 2015 at 21:10, Peter Mogensen <apm@xxxxxxx> wrote:
So ... I can easily get the current txid of the SELECT transaction by
calling txid_current().
Note that by doing so, you force txid allocation for a read-only query that
might otherwise not need one, which increases your txid burn rate and
decreases time until you need to do wraparound-protection vacuuming.
The same is not true for txid_snapshot_xmin() is it?
I mean ... I really don't need the actual txid of a SELECT statement.
Only to ensure that it's never than any invalidation event.
So it's enough to just use txid_snapshot_xmin() ... at the cost of
possibly not caching new values in a small window after invalidation.
/Peter
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