From 5788ff1f0ba6eed88d62d41e8a7f4093def73d95 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=81lvaro=20Herrera?= <alvherre@kurilemu.de>
Date: Thu, 2 Apr 2026 20:59:15 +0200
Subject: [PATCH v50 5/8] support repacking tables with exclusion constraints

---
 src/backend/commands/repack.c | 78 +++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)

diff --git a/src/backend/commands/repack.c b/src/backend/commands/repack.c
index 73eadd1ff4a..03829892d57 100644
--- a/src/backend/commands/repack.c
+++ b/src/backend/commands/repack.c
@@ -49,6 +49,7 @@
 #include "catalog/namespace.h"
 #include "catalog/objectaccess.h"
 #include "catalog/pg_am.h"
+#include "catalog/pg_constraint.h"
 #include "catalog/pg_control.h"
 #include "catalog/pg_inherits.h"
 #include "catalog/toasting.h"
@@ -199,6 +200,8 @@ static void rebuild_relation_finish_concurrent(Relation NewHeap, Relation OldHea
 											   TransactionId frozenXid,
 											   MultiXactId cutoffMulti);
 static List *build_new_indexes(Relation NewHeap, Relation OldHeap, List *OldIndexes);
+static void copy_index_constraints(Relation old_index, Oid new_index_id,
+								   Oid new_heap_id);
 static Relation process_single_relation(RepackStmt *stmt,
 										LOCKMODE lockmode,
 										bool isTopLevel,
@@ -3211,6 +3214,7 @@ build_new_indexes(Relation NewHeap, Relation OldHeap, List *OldIndexes)
 									 false);
 		newindex = index_create_copy(NewHeap, false, oldindex,
 									 ind->rd_rel->reltablespace, newName);
+		copy_index_constraints(ind, newindex, RelationGetRelid(NewHeap));
 		result = lappend_oid(result, newindex);
 
 		index_close(ind, NoLock);
@@ -3219,6 +3223,80 @@ build_new_indexes(Relation NewHeap, Relation OldHeap, List *OldIndexes)
 	return result;
 }
 
+/*
+ * Create a transient copy of a constraint -- supported by a transient
+ * copy of the index that supports the original constraint.
+ *
+ * When repacking a table that contains exclusion constraints, the executor
+ * relies on these constraints being properly catalogued.  These copies are
+ * to support that.
+ *
+ * We don't need the constraints for anything else (the original constraints
+ * will be there once repack completes), so we add pg_depend entries so that
+ * the are dropped when the transient table is dropped.
+ */
+static void
+copy_index_constraints(Relation old_index, Oid new_index_id, Oid new_heap_id)
+{
+	ScanKeyData skey;
+	Relation	rel;
+	TupleDesc	desc;
+	SysScanDesc scan;
+	HeapTuple	tup;
+	ObjectAddress	objrel;
+
+	rel = table_open(ConstraintRelationId, RowExclusiveLock);
+	ObjectAddressSet(objrel, RelationRelationId, new_heap_id);
+
+	/*
+	 * Retrieve the constraints supported by the old index and create an
+	 * identical one that points to the new index.
+	 */
+	ScanKeyInit(&skey,
+				Anum_pg_constraint_conrelid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(old_index->rd_index->indrelid));
+	scan = systable_beginscan(rel, ConstraintRelidTypidNameIndexId, true,
+							  NULL, 1, &skey);
+	desc = RelationGetDescr(rel);
+	while (HeapTupleIsValid(tup = systable_getnext(scan)))
+	{
+		Form_pg_constraint conform = (Form_pg_constraint) GETSTRUCT(tup);
+		Oid			oid;
+		Datum		values[Natts_pg_constraint] = {0};
+		bool		nulls[Natts_pg_constraint] = {0};
+		bool		replaces[Natts_pg_constraint] = {0};
+		HeapTuple	new_tup;
+		ObjectAddress objcon;
+
+		if (conform->conindid != RelationGetRelid(old_index))
+			continue;
+
+		oid = GetNewOidWithIndex(rel, ConstraintOidIndexId,
+								 Anum_pg_constraint_oid);
+		values[Anum_pg_constraint_oid - 1] = ObjectIdGetDatum(oid);
+		replaces[Anum_pg_constraint_oid - 1] = true;
+		values[Anum_pg_constraint_conrelid - 1] = ObjectIdGetDatum(new_heap_id);
+		replaces[Anum_pg_constraint_conrelid - 1] = true;
+		values[Anum_pg_constraint_conindid - 1] = ObjectIdGetDatum(new_index_id);
+		replaces[Anum_pg_constraint_conindid - 1] = true;
+
+		new_tup = heap_modify_tuple(tup, desc, values, nulls, replaces);
+
+		/* Insert it into the catalog. */
+		CatalogTupleInsert(rel, new_tup);
+
+		/* Create a dependency so it's removed when we drop the new heap. */
+		ObjectAddressSet(objcon, ConstraintRelationId, oid);
+		recordDependencyOn(&objcon, &objrel, DEPENDENCY_AUTO);
+	}
+	systable_endscan(scan);
+
+	table_close(rel, RowExclusiveLock);
+
+	CommandCounterIncrement();
+}
+
 /*
  * Try to start a background worker to perform logical decoding of data
  * changes applied to relation while REPACK CONCURRENTLY is copying its
-- 
2.47.3