Sort dump objects independent of OIDs, for the 7 holdout object types.

pg_dump sorts objects by their logical names, e.g. (nspname, relname,
tgname), before dependency-driven reordering.  That removes one source
of logically-identical databases differing in their schema-only dumps.
In other words, it helps with schema diffing.  The logical name sort
ignored essential sort keys for constraints, operators, PUBLICATION
... FOR TABLE, PUBLICATION ... FOR TABLES IN SCHEMA, operator classes,
and operator families.  pg_dump's sort then depended on object OID,
yielding spurious schema diffs.  After this change, OIDs affect dump
order only in the event of catalog corruption.  While pg_dump also
wrongly ignored pg_collation.collencoding, CREATE COLLATION restrictions
have been keeping that imperceptible in practical use.

Use techniques like we use for object types already having full sort key
coverage.  Where the pertinent queries weren't fetching the ignored sort
keys, this adds columns to those queries and stores those keys in memory
for the long term.

The ignorance of sort keys became more problematic when commit
172259afb563d35001410dc6daad78b250924038 added a schema diff test
sensitive to it.  Buildfarm member hippopotamus witnessed that.
However, dump order stability isn't a new goal, and this might avoid
other dump comparison failures.  Hence, back-patch to v13 (all supported
versions).

Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Discussion: https://postgr.es/m/20250707192654.9e.nmisch@google.com
Backpatch-through: 13

1 files changed, 61 insertions, 18 deletions

diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 4b13669f450..29d37158a38 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -1767,6 +1767,13 @@ selectDumpableProcLang(ProcLangInfo *plang, Archive *fout)
 static void
 selectDumpableAccessMethod(AccessMethodInfo *method, Archive *fout)
 {
+	/* see getAccessMethods() comment about v9.6. */
+	if (fout->remoteVersion < 90600)
+	{
+		method->dobj.dump = DUMP_COMPONENT_NONE;
+		return;
+	}
+
 	if (checkExtensionMembership(&method->dobj, fout))
 		return;					/* extension membership overrides all else */
 
@@ -5325,6 +5332,8 @@ getOperators(Archive *fout, int *numOprs)
 	int			i_oprnamespace;
 	int			i_rolname;
 	int			i_oprkind;
+	int			i_oprleft;
+	int			i_oprright;
 	int			i_oprcode;
 
 	/*
@@ -5336,6 +5345,8 @@ getOperators(Archive *fout, int *numOprs)
 					  "oprnamespace, "
 					  "(%s oprowner) AS rolname, "
 					  "oprkind, "
+					  "oprleft, "
+					  "oprright, "
 					  "oprcode::oid AS oprcode "
 					  "FROM pg_operator",
 					  username_subquery);
@@ -5353,6 +5364,8 @@ getOperators(Archive *fout, int *numOprs)
 	i_oprnamespace = PQfnumber(res, "oprnamespace");
 	i_rolname = PQfnumber(res, "rolname");
 	i_oprkind = PQfnumber(res, "oprkind");
+	i_oprleft = PQfnumber(res, "oprleft");
+	i_oprright = PQfnumber(res, "oprright");
 	i_oprcode = PQfnumber(res, "oprcode");
 
 	for (i = 0; i < ntups; i++)
@@ -5367,6 +5380,8 @@ getOperators(Archive *fout, int *numOprs)
 						  atooid(PQgetvalue(res, i, i_oprnamespace)));
 		oprinfo[i].rolname = pg_strdup(PQgetvalue(res, i, i_rolname));
 		oprinfo[i].oprkind = (PQgetvalue(res, i, i_oprkind))[0];
+		oprinfo[i].oprleft = atooid(PQgetvalue(res, i, i_oprleft));
+		oprinfo[i].oprright = atooid(PQgetvalue(res, i, i_oprright));
 		oprinfo[i].oprcode = atooid(PQgetvalue(res, i, i_oprcode));
 
 		/* Decide whether we want to dump it */
@@ -5407,6 +5422,7 @@ getCollations(Archive *fout, int *numCollations)
 	int			i_collname;
 	int			i_collnamespace;
 	int			i_rolname;
+	int			i_collencoding;
 
 	/* Collations didn't exist pre-9.1 */
 	if (fout->remoteVersion < 90100)
@@ -5424,7 +5440,8 @@ getCollations(Archive *fout, int *numCollations)
 
 	appendPQExpBuffer(query, "SELECT tableoid, oid, collname, "
 					  "collnamespace, "
-					  "(%s collowner) AS rolname "
+					  "(%s collowner) AS rolname, "
+					  "collencoding "
 					  "FROM pg_collation",
 					  username_subquery);
 
@@ -5440,6 +5457,7 @@ getCollations(Archive *fout, int *numCollations)
 	i_collname = PQfnumber(res, "collname");
 	i_collnamespace = PQfnumber(res, "collnamespace");
 	i_rolname = PQfnumber(res, "rolname");
+	i_collencoding = PQfnumber(res, "collencoding");
 
 	for (i = 0; i < ntups; i++)
 	{
@@ -5452,6 +5470,7 @@ getCollations(Archive *fout, int *numCollations)
 			findNamespace(fout,
 						  atooid(PQgetvalue(res, i, i_collnamespace)));
 		collinfo[i].rolname = pg_strdup(PQgetvalue(res, i, i_rolname));
+		collinfo[i].collencoding = atoi(PQgetvalue(res, i, i_collencoding));
 
 		/* Decide whether we want to dump it */
 		selectDumpableObject(&(collinfo[i].dobj), fout);
@@ -5561,19 +5580,28 @@ getAccessMethods(Archive *fout, int *numAccessMethods)
 	int			i_amhandler;
 	int			i_amtype;
 
-	/* Before 9.6, there are no user-defined access methods */
-	if (fout->remoteVersion < 90600)
-	{
-		*numAccessMethods = 0;
-		return NULL;
-	}
-
 	query = createPQExpBuffer();
 
-	/* Select all access methods from pg_am table */
-	appendPQExpBufferStr(query, "SELECT tableoid, oid, amname, amtype, "
-						 "amhandler::pg_catalog.regproc AS amhandler "
-						 "FROM pg_am");
+	/*
+	 * Select all access methods from pg_am table.  v9.6 introduced CREATE
+	 * ACCESS METHOD, so earlier versions usually have only built-in access
+	 * methods.  v9.6 also changed the access method API, replacing dozens of
+	 * pg_am columns with amhandler.  Even if a user created an access method
+	 * by "INSERT INTO pg_am", we have no way to translate pre-v9.6 pg_am
+	 * columns to a v9.6+ CREATE ACCESS METHOD.  Hence, before v9.6, read
+	 * pg_am just to facilitate findAccessMethodByOid() providing the
+	 * OID-to-name mapping.
+	 */
+	appendPQExpBufferStr(query, "SELECT tableoid, oid, amname, ");
+	if (fout->remoteVersion >= 90600)
+		appendPQExpBufferStr(query,
+							 "amtype, "
+							 "amhandler::pg_catalog.regproc AS amhandler ");
+	else
+		appendPQExpBufferStr(query,
+							 "'i'::pg_catalog.\"char\" AS amtype, "
+							 "'-'::pg_catalog.regproc AS amhandler ");
+	appendPQExpBufferStr(query, "FROM pg_am");
 
 	res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
 
@@ -5631,6 +5659,7 @@ getOpclasses(Archive *fout, int *numOpclasses)
 	OpclassInfo *opcinfo;
 	int			i_tableoid;
 	int			i_oid;
+	int			i_opcmethod;
 	int			i_opcname;
 	int			i_opcnamespace;
 	int			i_rolname;
@@ -5640,11 +5669,20 @@ getOpclasses(Archive *fout, int *numOpclasses)
 	 * system-defined opclasses at dump-out time.
 	 */
 
-	appendPQExpBuffer(query, "SELECT tableoid, oid, opcname, "
-					  "opcnamespace, "
-					  "(%s opcowner) AS rolname "
-					  "FROM pg_opclass",
-					  username_subquery);
+	if (fout->remoteVersion >= 80300)
+		appendPQExpBuffer(query, "SELECT tableoid, oid, "
+						  "opcmethod, opcname, "
+						  "opcnamespace, "
+						  "(%s opcowner) AS rolname "
+						  "FROM pg_opclass",
+						  username_subquery);
+	else
+		appendPQExpBuffer(query, "SELECT tableoid, oid, "
+						  "opcamid AS opcmethod, opcname, "
+						  "opcnamespace, "
+						  "(%s opcowner) AS rolname "
+						  "FROM pg_opclass",
+						  username_subquery);
 
 	res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
 
@@ -5655,6 +5693,7 @@ getOpclasses(Archive *fout, int *numOpclasses)
 
 	i_tableoid = PQfnumber(res, "tableoid");
 	i_oid = PQfnumber(res, "oid");
+	i_opcmethod = PQfnumber(res, "opcmethod");
 	i_opcname = PQfnumber(res, "opcname");
 	i_opcnamespace = PQfnumber(res, "opcnamespace");
 	i_rolname = PQfnumber(res, "rolname");
@@ -5669,6 +5708,7 @@ getOpclasses(Archive *fout, int *numOpclasses)
 		opcinfo[i].dobj.namespace =
 			findNamespace(fout,
 						  atooid(PQgetvalue(res, i, i_opcnamespace)));
+		opcinfo[i].opcmethod = atooid(PQgetvalue(res, i, i_opcmethod));
 		opcinfo[i].rolname = pg_strdup(PQgetvalue(res, i, i_rolname));
 
 		/* Decide whether we want to dump it */
@@ -5706,6 +5746,7 @@ getOpfamilies(Archive *fout, int *numOpfamilies)
 	OpfamilyInfo *opfinfo;
 	int			i_tableoid;
 	int			i_oid;
+	int			i_opfmethod;
 	int			i_opfname;
 	int			i_opfnamespace;
 	int			i_rolname;
@@ -5724,7 +5765,7 @@ getOpfamilies(Archive *fout, int *numOpfamilies)
 	 * system-defined opfamilies at dump-out time.
 	 */
 
-	appendPQExpBuffer(query, "SELECT tableoid, oid, opfname, "
+	appendPQExpBuffer(query, "SELECT tableoid, oid, opfmethod, opfname, "
 					  "opfnamespace, "
 					  "(%s opfowner) AS rolname "
 					  "FROM pg_opfamily",
@@ -5740,6 +5781,7 @@ getOpfamilies(Archive *fout, int *numOpfamilies)
 	i_tableoid = PQfnumber(res, "tableoid");
 	i_oid = PQfnumber(res, "oid");
 	i_opfname = PQfnumber(res, "opfname");
+	i_opfmethod = PQfnumber(res, "opfmethod");
 	i_opfnamespace = PQfnumber(res, "opfnamespace");
 	i_rolname = PQfnumber(res, "rolname");
 
@@ -5753,6 +5795,7 @@ getOpfamilies(Archive *fout, int *numOpfamilies)
 		opfinfo[i].dobj.namespace =
 			findNamespace(fout,
 						  atooid(PQgetvalue(res, i, i_opfnamespace)));
+		opfinfo[i].opfmethod = atooid(PQgetvalue(res, i, i_opfmethod));
 		opfinfo[i].rolname = pg_strdup(PQgetvalue(res, i, i_rolname));
 
 		/* Decide whether we want to dump it */