The connection that is executing the SELECT 1 are generally open for 1-5
hours before they are killed. The specific connection only executes
SELECT 1. The transaction is simply BEGIN, and then SELECT 1's, no
other query is executed.
The updates we make to the primary database are quiet large, usually
several megabytes.
Alex
On 4/2/2012 11:49 PM, Heikki Linnakangas wrote:
On 03.04.2012 02:23, amatzin...@experts-exchange.com wrote:
On a hot standby database, while the primary is being updated,
Postgres will
randomly kill a process which is performing a "Select 1" command.
The error is this:
2012-04-02 13:36:13.269
PDT,"smxuser","smxprd1",39523,"127.0.0.1:57893",4f79ffad.9a63,1,"",2012-04-02
12:36:13 PDT,3/32,0,FATAL,40001,"terminating connection due to
conflict with
recovery","User query might have needed to see row versions that must be
removed.","In a moment you should be able to reconnect to the
database and
repeat your command.",,,,,,,""
We have 5 hot standby's set up, which all preform this SELECT 1, and
postgres kills them across all standby's.
There should never be a situation that SELECT 1 is in conflict with
data, as
it it never using any table in the database.
The system doesn't make a difference between queries like "SELECT 1"
that don't access any tables, and those that do. Even if "SELECT 1"
doesn't access any tables, a subsequent statement in the same
transaction might.
I'm assuming that those "SELECT 1"s were issued in transactions that
had been open for a long time, because you shouldn't get recovery
conflicts with very short transactions, in practice anyway.
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