问题
I created multiple posts in the forum about the performance problem that I have but now after i made some tests and gathered all the info that is needed I'm creating this post.
I have performance issues with two big tables. Those tables are located on an oracle remote database. I'm running the quert :
insert into local_postgresql_table select * from oracle_remote_table.
The first table has 45M records and its size is 23G. The import of the data from the oracle remote database is taking 1 hour and 38 minutes. After that I create 13 regular indexes on the table and it takes 10 minutes per table ->2 hours and 10 minutes in total.
The second table has 29M records and its size is 26G. The import of the data from the oracle remote database is taking 2 hours and 30 minutes. The creation of the indexes takes 1 hours and 30 minutes (some are indexes on one column and the creation takes 5 min and some are indexes on multiples column and it takes 11 min.
Those operation are very problematic for me and I'm searching for a solution to improve the performance. The parameters I assigned :
min_parallel_relation_size = 200MB
max_parallel_workers_per_gather = 5
max_worker_processes = 8
effective_cache_size = 2500MB
work_mem = 16MB
maintenance_work_mem = 1500MB
shared_buffers = 2000MB
RAM : 5G
CPU CORES : 8
-I tried running select count(*) from table in oracle and in postgresql the running time is almost equal.
-Before importing the data I drop the indexes and the constraints.
-I tried to copy a 23G file from the oracle server to the postgresql server and it took me 12 minutes.
Please advice how can I continue ? How can I improve something in this operation ?
来源：https://stackoverflow.com/questions/45669697/slow-cross-loading-from-oracle-oracle-fdw-into-postgresql