when start a new backend or restart the DB, agg operation will get a null value at first time

[junfenglu2016]

[pgrel@centos01 ~]$ psql -h /pgreltmp/ postgres
psql (9.6.2)
Type "help" for help.

postgres=# select sum(review_rating) from vops_customer_reviews ;
sum

(1 row)

postgres=# select sum(review_rating) from vops_customer_reviews ;
sum

2602248
(1 row)

[knizhnik]

I think that first result was produced when vops extension is not yet loaded. This problems is explained in VOPS documentation. Two possible workarounds:

1. Add VOPS to shared_preload_libraries list/.
2. Call vops_initialize() before any access to table with VOPS tiles.