Re: using index to speedup add not null constraints to a table

Hi.

In get_relation_info, we have:
/*
* If the index is valid, but cannot yet be used, ignore it; but
* mark the plan we are generating as transient. See
* src/backend/access/heap/README.HOT for discussion.
*/
if (index->indcheckxmin &&

!TransactionIdPrecedes(HeapTupleHeaderGetXmin(indexRelation->rd_indextuple->t_data),
TransactionXmin))
{
root->glob->transientPlan = true;
index_close(indexRelation, NoLock);
continue;
}
So I did the same thing in index_check_notnull.

As the reason mentioned in [1], using indexscan to verify not-null can
only apply to the leading column of the index.
So we only need to do one ScanKeyEntryInitialize for indexscan

[1]: https://www.postgresql.org/message-id/CACJufxFae2f%3D_egVwGGvGFHMTU%3DPu7Akb-e_JMEsUCsHRT75Jw%40mail.gmail.com

--
jian
https://www.enterprisedb.com/