-
-
--- xid_to_int4 converts a PostgreSQL transaction ID (xid) to a 32-bit integer
--- which can then be used to efficiently find rows which have changed between
--- two given transactions. This is currently used by Osmosis to extract a
--- stream of edits for "diff replication" **HOWEVER** this is a pain point, as
--- (ab)using the xid in this way is _not_ supported or recommended by Postgres
--- devs. It is preventing us upgrading to PostgreSQL version 10+, and will
--- hopefully be replaced Real Soon Now.
---
--- From the Osmosis distribution by Brett Henderson:
--- https://github.com/openstreetmap/osmosis/blob/master/package/script/contrib/apidb_0.6_osmosis_xid_indexing.sql
-CREATE OR REPLACE FUNCTION xid_to_int4(t xid)
- RETURNS integer
- AS
-$$
-DECLARE
- tl bigint;
- ti int;
-BEGIN
- tl := t;
-
- IF tl >= 2147483648 THEN
- tl := tl - 4294967296;
- END IF;
-
- ti := tl;
-
- RETURN ti;
-END;
-$$ LANGUAGE 'plpgsql' IMMUTABLE STRICT;