On 01.03.2012 18:40, Simon Riggs wrote:
On Sun, Feb 26, 2012 at 7:16 PM, Heikki Linnakangas
<heikki.linnakan...@enterprisedb.com> wrote:
On 24.02.2012 22:55, Simon Riggs wrote:
What exactly does it do? Previously, we optimised COPY when it was
loading data into a newly created table or a freshly truncated table.
This patch extends that and actually sets the tuple header flag as
HEAP_XMIN_COMMITTED during the load. Doing so is simple 2 lines of
code. The patch also adds some tests for corner cases that would make
that action break MVCC - though those cases are minor and typical data
loads will benefit fully from this.
This doesn't work with subtransactions:
...
The query should return the row copied in the same subtransaction.
Thanks for pointing that out.
New patch with corrected logic and test case attached.
It's still broken:
-- create test table and file
create table a as select 1 as id;
copy a to '/tmp/a';
-- start test
postgres=# begin;
BEGIN
postgres=# truncate a;
TRUNCATE TABLE
postgres=# savepoint sp1;
SAVEPOINT
postgres=# copy a from '/tmp/a';
COPY 1
postgres=# select * from a;
id
----
1
(1 row)
postgres=# rollback to savepoint sp1;
ROLLBACK
postgres=# select * from a;
id
----
1
(1 row)
That last select should not have seen the tuple.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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