diff --git a/swh/provenance/postgresql/provenance.py b/swh/provenance/postgresql/provenance.py
--- a/swh/provenance/postgresql/provenance.py
+++ b/swh/provenance/postgresql/provenance.py
@@ -193,12 +193,21 @@
                         """
                     psycopg2.extras.execute_values(self.cursor, sql, dsts)
 
-                sql = """
-                    SELECT * FROM swh_provenance_relation_add(
-                        %s, %s, %s, %s::rel_row[]
-                    )
-                """
-                self.cursor.execute(sql, (rel_table, src_table, dst_table, rows))
+                # Put the next three queries in a manual single transaction:
+                # they use the same temp table
+                with self.conn:
+                    with self.conn.cursor() as cur:
+                        cur.execute("SELECT swh_mktemp_relation_add()")
+                        psycopg2.extras.execute_values(
+                            cur,
+                            sql=(
+                                "INSERT INTO tmp_relation_add (src, dst, path) "
+                                "VALUES %s"
+                            ),
+                            argslist=rows,
+                        )
+                        sql = "SELECT swh_provenance_relation_add_from_temp(%s, %s, %s)"
+                        cur.execute(sql, (rel_table, src_table, dst_table))
             return True
         except:  # noqa: E722
             # Unexpected error occurred, rollback all changes and log message
diff --git a/swh/provenance/sql/30-schema.sql b/swh/provenance/sql/30-schema.sql
--- a/swh/provenance/sql/30-schema.sql
+++ b/swh/provenance/sql/30-schema.sql
@@ -39,9 +39,6 @@
 );
 comment on type rel_flt is 'Relation get filter types';
 
--- a relation entry row, i.e. sr/dst Git object ID and optional UNIX path
-create type rel_row as (src sha1_git, dst sha1_git, path unix_path);
-
 -- entity tables
 create table content
 (
diff --git a/swh/provenance/sql/40-funcs.sql b/swh/provenance/sql/40-funcs.sql
--- a/swh/provenance/sql/40-funcs.sql
+++ b/swh/provenance/sql/40-funcs.sql
@@ -2,6 +2,16 @@
 select position('denormalized' in swh_get_dbflavor()::text) = 0 as dbflavor_norm \gset
 select position('with-path' in swh_get_dbflavor()::text) != 0 as dbflavor_with_path \gset
 
+create or replace function swh_mktemp_relation_add() returns void
+    language sql
+as $$
+    create temp table tmp_relation_add (
+        src sha1_git not null,
+        dst sha1_git not null,
+        path unix_path
+    ) on commit drop
+$$;
+
 \if :dbflavor_norm
 
 \if :dbflavor_with_path
@@ -77,8 +87,8 @@
     order by date, revision, origin, path limit early_cut
 $$;
 
-create or replace function swh_provenance_relation_add(
-    rel_table regclass, src_table regclass, dst_table regclass, rel_data rel_row[]
+create or replace function swh_provenance_relation_add_from_temp(
+    rel_table regclass, src_table regclass, dst_table regclass
 )
     returns void
     language plpgsql
@@ -92,7 +102,7 @@
             lock table only location;
             insert into location(path)
               select V.path
-              from unnest(rel_data) as V
+              from tmp_relation_add as V
             on conflict (path) do nothing;
 
             select_fields := 'D.id, L.id';
@@ -106,13 +116,13 @@
             'lock table only %s;
              insert into %s
                select S.id, ' || select_fields || '
-               from unnest($1) as V
+               from tmp_relation_add as V
                inner join %s as S on (S.sha1 = V.src)
                inner join %s as D on (D.sha1 = V.dst)
                ' || join_location || '
              on conflict do nothing',
             rel_table, rel_table, src_table, dst_table
-        ) using rel_data;
+        );
     end;
 $$;
 
@@ -235,8 +245,8 @@
     order by date, revision, origin, path limit early_cut
 $$;
 
-create or replace function swh_provenance_relation_add(
-    rel_table regclass, src_table regclass, dst_table regclass, rel_data rel_row[]
+create or replace function swh_provenance_relation_add_from_temp(
+    rel_table regclass, src_table regclass, dst_table regclass
 )
     returns void
     language plpgsql
@@ -247,12 +257,12 @@
             'lock table only %s;
              insert into %s
                select S.id, D.id
-               from unnest($1) as V
+               from tmp_relation_add as V
                inner join %s as S on (S.sha1 = V.src)
                inner join %s as D on (D.sha1 = V.dst)
              on conflict do nothing',
             rel_table, rel_table, src_table, dst_table
-        ) using rel_data;
+        );
     end;
 $$;
 
@@ -398,8 +408,8 @@
     order by date, revision, origin, path limit early_cut
 $$;
 
-create or replace function swh_provenance_relation_add(
-    rel_table regclass, src_table regclass, dst_table regclass, rel_data rel_row[]
+create or replace function swh_provenance_relation_add_from_temp(
+    rel_table regclass, src_table regclass, dst_table regclass
 )
     returns void
     language plpgsql
@@ -415,7 +425,7 @@
             lock table only location;
             insert into location(path)
               select V.path
-              from unnest(rel_data) as V
+              from tmp_relation_add as V
             on conflict (path) do nothing;
 
             select_fields := 'array_agg((D.id, L.id)::rel_dst)';
@@ -441,14 +451,14 @@
             'lock table only %s;
              insert into %s
                select S.id, ' || select_fields || '
-               from unnest($1) as V
+               from tmp_relation_add as V
                inner join %s as S on (S.sha1 = V.src)
                inner join %s as D on (D.sha1 = V.dst)
                ' || join_location || '
                ' || group_entries || '
              on conflict ' || on_conflict,
             rel_table, rel_table, src_table, dst_table
-        ) using rel_data;
+        );
     end;
 $$;
 
@@ -600,8 +610,8 @@
     order by date, revision, origin, path limit early_cut
 $$;
 
-create or replace function swh_provenance_relation_add(
-    rel_table regclass, src_table regclass, dst_table regclass, rel_data rel_row[]
+create or replace function swh_provenance_relation_add_from_temp(
+    rel_table regclass, src_table regclass, dst_table regclass
 )
     returns void
     language plpgsql
@@ -634,13 +644,13 @@
             'lock table only %s;
              insert into %s
                select S.id, ' || select_fields || '
-               from unnest($1) as V
+               from tmp_relation_add as V
                inner join %s as S on (S.sha1 = V.src)
                inner join %s as D on (D.sha1 = V.dst)
                ' || group_entries || '
              on conflict ' || on_conflict,
             rel_table, rel_table, src_table, dst_table
-        ) using rel_data;
+        );
     end;
 $$;