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commit    c9babbc8816a4f5d5894eda555e39ba30781322f
Author:   Peter Eisentraut <peter@eisentraut.org>
Date:     Tue Mar 17 13:06:53 2026 +0000

    Dump labels in reproducible order
    
    In pg_get_propgraphdef(), sort the labels before writing out, for a
    consistent dump order.  Also, since we now have a list, we can get rid
    of the separate table scan to get the count.
    
    Co-authored-by: Peter Eisentraut <peter@eisentraut.org>
    Co-authored-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
    Co-authored-by: Andrew Dunstan <andrew@dunslane.net>
    Reviewed-by: Junwang Zhao <zhjwpku@gmail.com>
    Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
    Discussion: https://www.postgresql.org/message-id/flat/a855795d-e697-4fa5-8698-d20122126567@eisentraut.org


 src/backend/utils/adt/ruleutils.c | 59 +++++++++++++++++++++++++++++----------
 1 file changed, 44 insertions(+), 15 deletions(-)

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 153a92fd3ea..7bc12589e40 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -1772,6 +1772,21 @@ make_propgraphdef_elements(StringInfo buf, Oid pgrelid, char pgekind)
 	table_close(pgerel, AccessShareLock);
 }
 
+struct oid_str_pair
+{
+	Oid			oid;
+	char	   *str;
+};
+
+static int
+list_oid_str_pair_cmp_by_str(const ListCell *p1, const ListCell *p2)
+{
+	struct oid_str_pair *v1 = lfirst(p1);
+	struct oid_str_pair *v2 = lfirst(p2);
+
+	return strcmp(v1->str, v2->str);
+}
+
 /*
  * Generates label and properties list.  Pass in the element OID, the element
  * alias, and the graph relation OID.  Result is appended to buf.
@@ -1784,6 +1799,7 @@ make_propgraphdef_labels(StringInfo buf, Oid elid, const char *elalias, Oid elre
 	SysScanDesc scan;
 	int			count;
 	HeapTuple	tup;
+	List	   *label_list = NIL;
 
 	pglrel = table_open(PropgraphElementLabelRelationId, AccessShareLock);
 
@@ -1792,38 +1808,51 @@ make_propgraphdef_labels(StringInfo buf, Oid elid, const char *elalias, Oid elre
 				BTEqualStrategyNumber, F_OIDEQ,
 				ObjectIdGetDatum(elid));
 
-	count = 0;
+	/*
+	 * We want to output the labels in a deterministic order.  So we first
+	 * read all the data, then sort, then print it.
+	 */
 	scan = systable_beginscan(pglrel, PropgraphElementLabelElementLabelIndexId, true, NULL, 1, scankey);
+
 	while ((tup = systable_getnext(scan)))
 	{
-		count++;
+		Form_pg_propgraph_element_label pgelform = (Form_pg_propgraph_element_label) GETSTRUCT(tup);
+		struct oid_str_pair *osp;
+
+		osp = palloc_object(struct oid_str_pair);
+		osp->oid = pgelform->oid;
+		osp->str = get_propgraph_label_name(pgelform->pgellabelid);
+
+		label_list = lappend(label_list, osp);
 	}
+
 	systable_endscan(scan);
+	table_close(pglrel, AccessShareLock);
 
-	scan = systable_beginscan(pglrel, PropgraphElementLabelElementLabelIndexId, true, NULL, 1, scankey);
+	count = list_length(label_list);
 
-	while ((tup = systable_getnext(scan)))
-	{
-		Form_pg_propgraph_element_label pgelform = (Form_pg_propgraph_element_label) GETSTRUCT(tup);
-		const char *labelname;
+	/* Each element has at least one label. */
+	Assert(count > 0);
 
-		labelname = get_propgraph_label_name(pgelform->pgellabelid);
+	/*
+	 * It is enough for the comparison function to compare just labels, since
+	 * all the labels of an element table should have distinct names.
+	 */
+	list_sort(label_list, list_oid_str_pair_cmp_by_str);
 
-		if (strcmp(labelname, elalias) == 0)
+	foreach_ptr(struct oid_str_pair, osp, label_list)
+	{
+		if (strcmp(osp->str, elalias) == 0)
 		{
 			/* If the default label is the only label, don't print anything. */
 			if (count != 1)
 				appendStringInfo(buf, " DEFAULT LABEL");
 		}
 		else
-			appendStringInfo(buf, " LABEL %s", quote_identifier(labelname));
+			appendStringInfo(buf, " LABEL %s", quote_identifier(osp->str));
 
-		make_propgraphdef_properties(buf, pgelform->oid, elrelid);
+		make_propgraphdef_properties(buf, osp->oid, elrelid);
 	}
-
-	systable_endscan(scan);
-
-	table_close(pglrel, AccessShareLock);
 }
 
 /*


[parent: 2c1a7d421f92]