* Konstantin Osipov <kostja@stripped> [10/04/23 18:02]:
> > If I understand correctly, the flag HA_EXTRA_WRITE_CAN_REPLACE implies
> > that handler::write_row can overwrite existing rows, if a duplicate is
> > found. That is what the comment states, and that is what I heard NDB
> > does in MySQL Cluster. If this is the case, then I assume that
> > handler::write_row returns success even when the row is overwritten.
> You can treat it in two ways:
> - it is merely a hint, and the server doesn't expect any change
> in the contract if it is set
> - it never actually worked.
I just checked the cluster storage engine code, and it seems that
the cluster is using this option as a hint to avoid extra round
trips. I checked the history, and the option was added
for the cluster engine.
It is becoming apparent now that this addition did not honour
the status information (i.e. was buggy).
> Both MyISAM and InnoDB engines ignore it,
> (check storage/myisam/mi_extra.c,
> storage/innobase/handler/ha_innodb.cc), which means you should do
> it as well.