crdb excessive IO CTE query plan

gistfile1.txt

    ⚬ Root
        ⚬ Count
        ⚬ Insert
        into = object_locations(store, id, disk, start, end, cksum)
        strategy = inserter
        ⚬ Render
        render = [column1, column2, unnest, unnest, unnest, CAST(_ AS BYTES)]
        ⚬ Project set
        render = [unnest(@6), unnest(@7), unnest(@8)]
        ⚬ Hash-join
        equality = (column2) = (id)
        type = inner
            ⚬ Scan buffer node
            label = buffer 1 (inputrows)
            ⚬ Scan buffer node
            label = buffer 2 (inserted_objects)
        ⚬ Subquery
        exec mode = all rows
        id = @S1
        original sql = VALUES (_, _::BYTES, _, _, _, ARRAY[_, _], ARRAY[_, _], ARRAY[_, _]), (__more10__)
        ⚬ Buffer node
        label = buffer 1 (inputrows)
        ⚬ Values
        row 0, expr = [_, _, _, _, _, _, _, _]
        row 1, expr = [_, _, _, _, _, _, _, _]
        row 10, expr = [_, _, _, _, _, _, _, _]
        row 2, expr = [_, _, _, _, _, _, _, _]
        row 3, expr = [_, _, _, _, _, _, _, _]
        row 4, expr = [_, _, _, _, _, _, _, _]
        row 5, expr = [_, _, _, _, _, _, _, _]
        row 6, expr = [_, _, _, _, _, _, _, _]
        row 7, expr = [_, _, _, _, _, _, _, _]
        row 8, expr = [_, _, _, _, _, _, _, _]
        row 9, expr = [_, _, _, _, _, _, _, _]
        size = 8 columns, 11 rows
        ⚬ Subquery
        exec mode = all rows
        id = @S2
        original sql = INSERT INTO objects(store, id, size) (SELECT DISTINCT ON (store, object_id) store, object_id, size FROM inputrows) ON CONFLICT (store, id) DO NOTHING RETURNING store, id
        ⚬ Buffer node
        label = buffer 2 (inserted_objects)
        ⚬ Spool
        ⚬ Run
        ⚬ Insert
        into = objects(store, id, size, flags, atime, chunks)
        strategy = inserter
        ⚬ Render
        render = [store, object_id, size, column23, column24, column25]
        ⚬ Filter
        filter = store IS _
        ⚬ Lookup-join
        table = objects@primary
        equality = (store, object_id) = (store, id)
        equality cols are key
        parallel
        type = left outer
        ⚬ Render
        render = [CAST(_ AS VARBIT), now()::INT8, CAST(_ AS JSONB), column1, column2, column5]
        ⚬ Distinct
        distinct on = column1, column2
        ⚬ Render
        render = [column1, column2, column5]
        ⚬ Scan buffer node
        label = buffer 1 (inputrows)
        ⚬ Subquery
        exec mode = all rows
        id = @S3
        original sql = INSERT INTO bucket_objects(store, oid, bucket, id) (SELECT store, object_id, bucket, bucket_id FROM inputrows) ON CONFLICT (store, oid, bucket, id) DO NOTHING RETURNING bucket, id
        ⚬ Buffer node
        label = buffer 3 (inserted_bucket_objects)
        ⚬ Spool
        ⚬ Render
        render = [bucket, id]
        ⚬ Run
        ⚬ Insert
        into = bucket_objects(store, oid, bucket, id, http_headers, ipacl, max_downloads, counter, atime)
        strategy = inserter
        ⚬ Render
        render = [store, object_id, bucket, bucket_id, column49, column49, column50, column51, column52]
        ⚬ Render
        render = [store, object_id, bucket, bucket_id, column49, column50, column51, column52]
        ⚬ Filter
        filter = store IS _
        ⚬ Lookup-join
        table = bucket_objects@ixnbi
        equality = (bucket, bucket_id) = (bucket, id)
        equality cols are key
        parallel
        pred = (@5 = @9) AND (@6 = @10)
        type = left outer
        ⚬ Render
        render = [CAST(_ AS JSONB), CAST(_ AS INT8), _, now()::INT8, column1, column2, column3, column4]
        ⚬ Scan buffer node
        label = buffer 1 (inputrows)