Fix operator family identifiers.

The previous code was broken, as an operator family name is only unique for a
given access method.

Thanks to Zacharias Knudsen for the report.  As seen in the bug report, it can
lead to false positive problem as the comparision was depending on the physical
tuple positions in the table.

Tests added to reproduce the problem in the pg_broken_extupgrade extension in
"head" version.  I wasn't able to reproduce it with only 2 operator families
though.  There is also another test to cover an actual diff with operator
families.

README.md

@@ -685,6 +685,14 @@ Some GUC changes leaked the script for version head-1.0--head-1.1:
           - upgraded has no value, while installed has
             + {rjuju=UC/rjuju}
 
+  - in opfamilies:
+    installed and upgraded both have 4 OpFamily but some mismatch in them:
+      1 OpFamily missing in installed:
+        - public.my_opf_btree USING btree
+
+      1 OpFamily missing in upgraded:
+        - public.my_opf_btree USING gin
+
   - in extra_queries:
     installed and upgraded both have 3 Resultset but some mismatch in them:
 SELECT 1 / (random() * 2)::int AS may_fail

src/extension/pg_opfamily.rs

@@ -15,7 +15,7 @@ use crate::{
 
 DbStruct! {
 	OpFamily:opfname:OpFamily {
-		opfname: Text = ("n.nspname || '.' || opf.opfname"),
+		opfname: Text = ("n.nspname || '.' || opf.opfname || ' USING ' || am.amname"),
 		opfmethod: Name = ("am.amname"),
 		opfowner: Name = ("r.rolname"),
 	}

tests/fixtures/pg_broken_extupgrade--head-1.0--head-1.1.sql

@@ -4,3 +4,8 @@
 SET work_mem = '321kB';
 SET LOCAL maintenance_work_mem TO '6666';
 SET LOCAL client_min_messages = WARNING;
+
+-- those 3 are just to validate that the am is used in the identifier
+ALTER OPERATOR FAMILY my_opf1 USING gist RENAME TO my_opf2;
+ALTER OPERATOR FAMILY my_opf1 USING gin RENAME TO my_opf2;
+ALTER OPERATOR FAMILY my_opf1 USING btree RENAME TO my_opf2;

tests/fixtures/pg_broken_extupgrade--head-1.0.sql

@@ -100,3 +100,8 @@ COMMENT ON AGGREGATE agg_1(int) IS 'smaller';
 CREATE POLICY popol0 ON tbl0 AS PERMISSIVE FOR ALL TO public USING (id > 0);
 CREATE SCHEMA nsp_1;
 CREATE SCHEMA nsp_2;
+CREATE OPERATOR FAMILY my_opf_btree USING btree;
+-- those 3 are just to validate that the am is used in the identifier
+CREATE OPERATOR FAMILY my_opf1 USING btree;
+CREATE OPERATOR FAMILY my_opf1 USING gin;
+CREATE OPERATOR FAMILY my_opf1 USING gist;

tests/fixtures/pg_broken_extupgrade--head-1.1.sql

@@ -113,3 +113,8 @@ CREATE POLICY popol0 ON tbl0 AS RESTRICTIVE FOR SELECT TO current_user USING (id
 CREATE SCHEMA nsp_1;
 CREATE SCHEMA nsp_2;
 REVOKE USAGE ON SCHEMA nsp_2 FROM public;
+CREATE OPERATOR FAMILY my_opf_btree USING gin;
+-- those 3 are just to validate that the am is used in the identifier
+CREATE OPERATOR FAMILY my_opf2 USING btree;
+CREATE OPERATOR FAMILY my_opf2 USING gin;
+CREATE OPERATOR FAMILY my_opf2 USING gist;