Add a comment explaining why we force physical removal of OIDs.

Noah Misch, slightly revised.

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 8a281968ad89aa6c4fe31e0aca1d6e9492bc20ab..8fa9d7fa7f11547d3b9f3d21b01978ee71ab4920 100644 (file)
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -4942,7 +4942,9 @@ ATExecDropColumn(List **wqueue, Relation rel, const char *colName,
 
    /*
     * If we dropped the OID column, must adjust pg_class.relhasoids and tell
-    * Phase 3 to physically get rid of the column.
+    * Phase 3 to physically get rid of the column.  We formerly left the
+    * column in place physically, but this caused subtle problems.  See
+    * http://archives.postgresql.org/pgsql-hackers/2009-02/msg00363.php
     */
    if (attnum == ObjectIdAttributeNumber)
    {