Re: Logical Replica ReorderBuffer Size Accounting Issues

I suspect the writes are updates to jsonb columns.  I can correlate bursts of writes of this form to the memory spikes:
UPDATE suspect_table

  SET jsonb_column = jsonb_column || $1,

         updated_at = $2

  WHERE ...

The update being added in $1 is typically a single new field.  The jsonb column is flat string key/value pairs, e.g. lots of {"key": "value", ...}.

The average size of the whole tuple in the suspect table is ~800 bytes (based on 10000 random samples), of which the jsonb column is 80%.

I have been trying to break into a walsender to inspect some tuple bufs directly and compare the ChangeSize vs GetTupleBuf size as you suggest, but it's proving a little tricky - I'll let you know if I have any luck here.

Thanks,

- Alex.