Re: Oracle data to PG

On 7/28/22 04:55, Dischner, Anton wrote:
>
> Hi Team,
>
> we are searching for a way to import a dump from an Oracle
> Installation into PostgreSQL.
>
> Ist not administrated by us, so foreing table or connect as an user
> (as ora2pg seems to need) is not an option.
>
> We had a look into
> https://www.enterprisedb.com/blog/the-complete-oracle-to-postgresql-migration-guide-tutorial-move-convert-database-oracle-alternative
>
> especially:
>
> * Ora2pg <http://ora2pg.darold.net/>—a robust migration tool that
> connects to an Oracle database, extracts schemas and tables and
> generates SQL scripts that can be loaded into Postgres.
> * Ora_migrator—an extension that  uses  an oracle_fdw foreign data
> wrapper to extract data from an Oracle database.
> * Orafce—this extension allows you to implement a number of Oracle
> functions in Postgres.  It also provides support for Oracle date
> formatting and additional Oracle data types.
> * EDB Migration Portal
> <https://www.enterprisedb.com/products/free-oracle-postgres-migration-tool>—a
> web-based service for migrating from Oracle to EDB Postgres
> Advanced Server
> <https://www.enterprisedb.com/products/edb-postgres-advanced-server-secure-ha-oracle-compatible>
> that features Assessment, Schema conversion and Compatibility
> reporting.
>
> we have to import data only.
>
> No indexes, PL/SQL or other stuff.
>
> Maybe it makes sense to install an Oracle Instance, import the data
> and then connect as a user and do the conversion.
>
> What are you hints and experiences to plan and accomplish this task?
>
> best
>
> Anton
>
Hi Anton,

Long time no see. Ora2pg can produce just the "CREATE TABLE/INDEX/VIEW"
statements from Oracle, translated to PgSQL vernacular. You will have to
be able to log onto the original Oracle instance, albeit as an
application owner.

Furthermore, Oracle has a free ODBC gateway which can be used to connect
to Postgres. What you need is an Oracle listener, not an entire
instance. Another thing that can be exceedingly useful is this:
https://osalvador.github.io/ReplicaDB/

You can extract Oracle data into CSV files and do COPY in PgSQL. I know
it works with Snowflake. There is no reason for it not to work witg
PgSQL as well. You will need some scripting, but it can be done.

Be aware of some key differences: Oracle doesn't store NULL values in
indexes. PostgreSQL does. The corollary is different behavior with the
unique, multi-column indexes. There are many more index types in PgSQL,
I find Bloom indexes exceptionally useful.

Good luck!

--
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
https://dbwhisperer.wordpress.com