Re: BUG #15934: pg_dump output in wrong order if custom operator class is used as subtype_opclass in a range type

I wrote:
> Clearly, we gotta upgrade pg_dump's intelligence about handling this
> dependency structure.  The most straightforward fix would involve
> promoting pg_amop (and pg_amproc) entries to be full DumpableObjects,
> but I'm apprehensive about the overhead that would add ...

After further thought, I realized we could fix it far less invasively
than that, by teaching getDependencies() to translate pg_depend entries
for the pg_amop/amproc rows to look like dependencies for their parent
opfamily.  This looks messy, but in a typical database without any
custom opclasses, it's actually really cheap, because there won't be
any pg_depend entries satisfying the classid conditions.

I wasn't looking forward to back-patching the other idea, but this
patch seems like it should be pretty painless.

Again, thanks for the report!

            regards, tom lane

diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 8a31672..0cc9ede 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -17911,14 +17911,45 @@ getDependencies(Archive *fout)
     query = createPQExpBuffer();

     /*
+     * Messy query to collect the dependency data we need.  Note that we
+     * ignore the sub-object column, so that dependencies of or on a column
+     * look the same as dependencies of or on a whole table.
+     *
      * PIN dependencies aren't interesting, and EXTENSION dependencies were
      * already processed by getExtensionMembership.
      */
     appendPQExpBufferStr(query, "SELECT "
                          "classid, objid, refclassid, refobjid, deptype "
                          "FROM pg_depend "
-                         "WHERE deptype != 'p' AND deptype != 'e' "
-                         "ORDER BY 1,2");
+                         "WHERE deptype != 'p' AND deptype != 'e'\n");
+
+    /*
+     * Since we don't treat pg_amop entries as separate DumpableObjects, we
+     * have to translate their dependencies into dependencies of their parent
+     * opfamily.  Ignore internal dependencies though, as those will point to
+     * their parent opclass, which we needn't consider here (and if we did,
+     * it'd just result in circular dependencies).  Also, "loose" opfamily
+     * entries will have dependencies on their parent opfamily, which we
+     * should drop since they'd likewise become useless self-dependencies.
+     * (But be sure to keep deps on *other* opfamilies; see amopsortfamily.)
+     */
+    appendPQExpBufferStr(query, "UNION ALL\n"
+                         "SELECT 'pg_opfamily'::regclass AS classid, amopfamily AS objid, refclassid, refobjid,
deptype" 
+                         "FROM pg_depend d, pg_amop o "
+                         "WHERE deptype NOT IN ('p', 'e', 'i') AND "
+                         "classid = 'pg_amop'::regclass AND objid = o.oid "
+                         "AND NOT (refclassid = 'pg_opfamily'::regclass AND amopfamily = refobjid)\n");
+
+    /* Likewise for pg_amproc entries */
+    appendPQExpBufferStr(query, "UNION ALL\n"
+                         "SELECT 'pg_opfamily'::regclass AS classid, amprocfamily AS objid, refclassid, refobjid,
deptype" 
+                         "FROM pg_depend d, pg_amproc p "
+                         "WHERE deptype NOT IN ('p', 'e', 'i') AND "
+                         "classid = 'pg_amproc'::regclass AND objid = p.oid "
+                         "AND NOT (refclassid = 'pg_opfamily'::regclass AND amprocfamily = refobjid)\n");
+
+    /* Sort the output for efficiency below */
+    appendPQExpBufferStr(query, "ORDER BY 1,2");

     res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);