Re: Report bytes and transactions actually sent downtream - Mailing list pgsql-hackers

> On Dec 17, 2025, at 13:55, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> wrote:
>
> Thanks for pointing this out. I have fixed it my code. However, at
> this point I am looking for a design review, especially to verify that
> the new implementation addresses Andres's concern raised in [1] while
> not introducing any design issues raised earlier e.g. those raised in
> threads [2], [3] and [4]
>
> [1] https://www.postgresql.org/message-id/zzidfgaowvlv4opptrcdlw57vmulnh7gnes4aerl6u35mirelm@tj2vzseptkjk
>>> [2] https://www.postgresql.org/message-id/CAA4eK1KzYaq9dcaa20Pv44ewomUPj_PbbeLfEnvzuXYMZtNw0A%40mail.gmail.com
>>> [3] https://www.postgresql.org/message-id/aNZ1T5vYC1BtKs4M@ip-10-97-1-34.eu-west-3.compute.internal
>>> [4] https://www.postgresql.org/message-id/CAExHW5tfVHABuv1moL_shp7oPrWmg8ha7T8CqwZxiMrKror7iw%40mail.gmail.com
>
> --
> Best Wishes,
> Ashutosh Bapat


Hi Ashutosh,

Yeah, I owe you a review. I committed to review this patch but I forgot, sorry about that.

From design perspective, I agree increasing counters should belong to the core, plugin should return properly values
followingthe contract. And I got some more comments: 

1. I just feel a bool return value might not be clear enough. For example:

```
-    ctx->callbacks.change_cb(ctx, txn, relation, change);
+    if (!ctx->callbacks.change_cb(ctx, txn, relation, change))
+        cache->filteredBytes += ReorderBufferChangeSize(change);
```

You increase filteredBytes when change_cb returns false. But if we look at pgoutput_change(), there are many reasons to
returnfalse. Counting all the cases to filteredBytes seems wrong. 

2.
```
-    ctx->callbacks.truncate_cb(ctx, txn, nrelations, relations, change);
+    if (!ctx->callbacks.truncate_cb(ctx, txn, nrelations, relations, change))
+        cache->filteredBytes += ReorderBufferChangeSize(change);
```

Row filter doesn’t impact TRUNCATE, why increase filteredBytes after truncate_cb()?

3.
```
-    ctx->callbacks.prepare_cb(ctx, txn, prepare_lsn);
+    if (ctx->callbacks.prepare_cb(ctx, txn, prepare_lsn))
+        cache->sentTxns++;
```

For 2-phase commit, it increase sentTxns after prepare_cb, and
```
+    if (ctx->callbacks.stream_abort_cb(ctx, txn, abort_lsn))
+        cache->sentTxns++;
```

If the transaction is aborted, sentTxns is increased again, which is confusing. Though for aborting there is some data
(anotification) is streamed, but I don’t think that should be counted as a transaction. 

After commit, sentTxns is also increased, so that, a 2-phase commit is counted as two transactions, which feels also
confusing.IMO, a 2-phase commit should still be counted as one transaction. 

4. You add sentBytes and filteredBytes. I am thinking if it makes sense to also add sentRows and filteredRows. Because
tablescould be big or small, bytes + rows could show a more clear picture to users. 

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/