Re: [PoC] pg_upgrade: allow to upgrade publisher node

On Tue, Oct 10, 2023 at 6:17 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> DecodeTXNNeedSkip(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
> Oid txn_dbid, RepOriginId origin_id)
> {
> - return (SnapBuildXactNeedsSkip(ctx->snapshot_builder, buf->origptr) ||
> - (txn_dbid != InvalidOid && txn_dbid != ctx->slot->data.database) ||
> - ctx->fast_forward || FilterByOrigin(ctx, origin_id));
> + bool need_skip;
> +
> + need_skip = (SnapBuildXactNeedsSkip(ctx->snapshot_builder, buf->origptr) ||
> + (txn_dbid != InvalidOid && txn_dbid != ctx->slot->data.database) ||
> + ctx->decoding_mode != DECODING_MODE_NORMAL ||
> + FilterByOrigin(ctx, origin_id));
> +
> + /* Set a flag if we are in the slient mode */
> + if (ctx->decoding_mode == DECODING_MODE_SILENT)
> + ctx->output_skipped = true;
> +
> + return need_skip;
>
> I think you need to set the new flag only when we are not skipping the
> transaction or in other words when we decide to process the
> transaction. Otherwise, how will you distinguish the case where the
> xact is already decoded and sent to client?
>

In the attached patch atop your v47*, I have changed it to show you
what I have in mind.

A few more comments:
=================
1.
+
+ /*
+ * Did the logical decoding context skip outputting any changes?
+ *
+ * This flag is used only when the context is in the silent mode.
+ */
+ bool output_skipped;
} LogicalDecodingContext;

This doesn't seem to convey the meaning to the caller. How about
processing_required? BTW, I have made this change as well in the
patch.

2.
@@ -295,7 +295,7 @@ xact_decode(LogicalDecodingContext *ctx,
XLogRecordBuffer *buf)
*/
if (TransactionIdIsValid(xid))
{
- if (!ctx->fast_forward)
+ if (ctx->decoding_mode != DECODING_MODE_FAST_FORWARD)
ReorderBufferAddInvalidations(reorder, xid,
buf->origptr,
invals->nmsgs,
@@ -303,7 +303,7 @@ xact_decode(LogicalDecodingContext *ctx,
XLogRecordBuffer *buf)
ReorderBufferXidSetCatalogChanges(ctx->reorder, xid,
buf->origptr);
}
- else if ((!ctx->fast_forward))
+ else if (ctx->decoding_mode != DECODING_MODE_FAST_FORWARD)
ReorderBufferImmediateInvalidation(ctx->reorder,
invals->nmsgs,
invals->msgs);

We don't to execute the invalidations even in silent mode. Looking at
this and other changes in the patch related to silent mode, I wonder
whether we really need to introduce 'silent_mode'. Can't we simply set
processing_required when 'fast_forward' mode is true and then let the
caller decide whether it needs to further process the WAL?

--
With Regards,
Amit Kapila.