Re: [PATCH] Use indexes on the subscriber when REPLICA IDENTITY is full on the publisher

Hi Amit, all


> wip_for_optimize_index_column_match
> +static bool
> +IndexContainsAnyRemoteColumn(IndexInfo  *indexInfo,
> + LogicalRepRelation  *remoterel)
> +{
> + for (int i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
> + {
>
> Wouldn't it be better to just check if the first column is not part of
> the remote column then we can skip that index?
>

Reading [1], I think I can follow what you suggest. So, basically,
if the leftmost column is not filtered, we have the following:

 but the entire index would have to be scanned, so in most cases the
> planner would prefer a sequential table scan over using the index.


So, in our case, we could follow a similar approach. If the leftmost column
of the index
is not sent over the wire from the pub, we can prefer the sequential scan.

Is my understanding of your suggestion accurate?


>
> In wip_optimize_for_non_pkey_non_ri_unique_index patch, irrespective
> of whether we want to retain this set of changes, the function name
> IsIdxSafeToSkipDuplicates() sounds better than
> IdxIsRelationIdentityOrPK() and we can even change the check to
> GetRelationIdentityOrPK() instead of separate checks replica index and
> PK. So, it would be better to include this part of the change (a.
> change the function name to IsIdxSafeToSkipDuplicates() and (b) change
> the check to use GetRelationIdentityOrPK()) in the main patch.
>
>
>
I agree that it is a good change. Added to v42

Thanks,
Onder KALACI



[1] https://www.postgresql.org/docs/current/indexes-multicolumn.html