Enhancements:

• Add support for COPY to foreign tables (from PostgreSQL v11 on). This caused a crash before, as reported by @jkldv.

• Add a new collation option for IMPORT FOREIGN SCHEMA that controls case folding. Patch by @sahapasci.

• Add support for Oracle XMLTYPE.

• Set V$SESSION_CONNECT_INFO.CLIENT_DRIVER to oracle_fdw. This makes it easier to identify the session on the Oracle side.

Bugfixes:

• Fix crash or bad results with pushed down join queries. The query target list can change during query planning, but oracle_fdw relied on the one from before. This bug only manifests in PostgreSQL v11. Bug found by @Jaime2ndQuadrant and fixed by @yamatattsu.

• Fix push-down of foreign scan conditions with variables belonging to other tables. This can lead to wrong results and warnings like:

  WARNING:  column number x of foreign table "y" does not exist in foreign Oracle table, will be replaced by NULL
  

• Fix crash in UPDATE or DELETE where the optimizer can deduce that no scan is required, for example with WHERE 1 = 0. Reported by @mrship.

• Fix crash or bad results in queries with IN or = ANY where the element type on the right-hand side is different from the left-hand side type.

• Add support for reading infinite NUMBERs. Oracle NUMBER has infinite values, which are represented as ~ and -~. Since PostgreSQL's numeric does not know infinity, map these values to NaN in this case. For real and double precision we can use the normal infinity values.

• The readonly option of IMPORT FOREIGN SCHEMA didn't work properly: When set to false, it would still create read-only foreign tables. Reported by @jacobdr.