Upgrade note:

When upgrading from an older version of oracle_fdw, make sure to run

ALTER EXTENSION oracle_fdw UPDATE;

after installing the extension.

Enhancements:

• Support PostgreSQL v13. Support for 9.2 and 9.1 is dropped.

• Add a function oracle_execute to execute arbitrary SQL statements on Oracle. The statements must not return a result (e.g. DDL statements).

• Add an option dblink for Oracle database links.
  The option can be used on foreign tables or with IMPORT FOREIGN SCHEMA.
  Patch by @nboullis.

• Add a column option strip_zeros that automatically strips ASCII 0 characters from strings. Per request from @Sascha8a.

• New IMPORT FOREIGN SCHEMA options max_long, sample_percent and prefetch. These set the corresponding options on imported tables.
  Suggested by @ferfebles.

• Add support for isolation levels other than SERIALIZABLE.
  This is mostly because Oracle's implementation of SERIALIZABLE is so buggy.
  Patch by @ThinkJ001.

Bugfixes:

• Fix bad results with uncorrelated subqueries.
  This affects queries have a foreign scan with a filter based on a subplan.
  Reported by @srakazmus.

• Fix Internal oracle_fdw error: encountered unknown node type 144.
  This can happen in plans involving tables with identity columns.
  Reported by @todoubaba.

• Don't throw an error if DML statements modify no rows.
  This might be caused by a trigger on the Oracle side.
  Reported by @radist-nt.

• Fix NCHAR and NVARCHAR2 handling.
  With single-byte Oracle character sets, this bug led to replacement characters being used for characters not in the database character set.
  Reported by @srakazmus, and @chrullrich helped with the fix.

• Report a proper error for INSERT ... ON CONFLICT on partitioned tables.
  Report and fix by @ibarwick.

• Fix INSERT ... RETURNING if a table partition is a foreign table.
  It used to return NULL values by mistake.
  Report and analysis by @ibarwick.