pinned projection checkpoint_epoch
I'm configuring some ETL into vertica and I want to give a try to pinned projections with global temp tables as it pointed out here
The code as follows:
CREATE GLOBAL TEMP TABLE test (
) NO PROJECTION;
CREATE PROJECTION test_pinned AS select * from test order by _id PINNED ;
The flow is like to load data into such table, transform data into another (regular not temporary) table, close session and discard changes on global temp table.
And it looks like everything works fine
But after all I figured out that checkpoint epoch is like freezes for such projection. I hzve created that table yesterday and now I have pinned projection with checkpoint_epoch 120K behind checkpoint_epoch of every other projection in database
projection_schema projection_id projection_name is_up_to_date checkpoint_epoch would_recover is_behind_ahm public 103582793949956170 test_pinned_b1 true 113399719 true true public 103582793949956038 test_pinned_b0 true 113399719 true true
current epoch,last good epoch and ahm are
current_epoch ahm_epoch last_good_epoch 113521540 113521264 113521454
Looks like low pinned projection epoch does not effect ahm.
Is it bad that pinned projection is too far behind? Does it lead to something bad?