I'm dealing with a Postgres table (called "lives") that contains records with columns for time_stamp, usr_id, transaction_id, and lives_remaining. I need a query that will give me the most recent lives_remaining total for each usr_id There are multiple users (distinct usr_id's) time_stamp is not a unique identifier: sometimes user even...
I'm using a query which generally executes in under a second, but sometimes takes between 10-40 seconds to finish. I'm actually not totally clear on how the subquery works, I just know that it works, in that it gives me 15 rows for each faverprofileid. I'm logging slow queries and it's telling me 5823244 rows were examined, which is odd...
It seems that on some of the servers that we have, the cost of hash joins, group by's and order by's is too low compared to the actual cost. I.e. often execution plans with index range scans outperform the former, but on explain plan the cost shows up as higher. Some further notes: I already set *optimizer_index_cost_adj* to 20 and it...