Re: Any optimizations using oracle_fdw with oracle tables that have clob columns?

On Thu, 2020-06-18 at 09:54 -0600, Hotmail wrote:
> We are moving a table (with almost a billion rows) to Postgres from Oracle using oracle_fdw.
> We have discovered that there is a single row fetch limitation in oracle when pulling a row
> that contains a clob column into Postgres.
>
> My question is, other than running multiple oracle_fdw parallel threads to speed up the data
> load are there any other optimizations that we may be unaware for oracle_fdw when working
> with Oracle clob columns?

No, this is a limitation of Oracle:

https://docs.oracle.com/en/database/oracle/oracle-database/19/lnoci/using-sql_statements-in-oci.html#GUID-7AE9DBE2-5316-4802-99D1-969B72823F02
"Prefetching is not in effect if LONG, LOB or Opaque Type columns (such as XMLType) are part of the query."

I could change the code to *not* use automatic prefetching and rather explicitly fetch
rows in bundles, but so far I have been too lazy to complicate the code with that.

Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com