From release notes:

The pg_namespace.aclitem column has been renamed to nspacl. pg_class now has a relpersistence column. New functions pg_encoding_to_char, pg_get_viewdef, and pg_get_keywords. The pg_tablespace table is now available. The type name "char" (with quotes) is recognized as an alias for CHAR. Session variable server_version_num is now available.

PRs:

• sql: add miscellaneous Postgres compatibility cockroach#18530
• sql: add pg_catalog.pg_get_viewdef cockroach#18618
• sql: new built-in generator pg_get_keywords cockroach#19127
• sql: Add server_version_num session variable cockroach#19405