Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Takahiro Itagaki <itagaki.takahiro@oss.ntt.co.jp> writes:
> > Instead, how about excluding columns in primary keys from table data?
>
> How will you implement "select * from mytable" ? Or even
> "select * from mytable where non_primary_key = something" ?
Use index full scans. We can do it even for now with enable_seqscan = off.
Of course, it requires an additional step to merge index keys and heap tuples.
Also, we're using the same technique for TOASTed values. The cost can be
compared with "select * from mytable where toasted_value = something", no?
> If you can't do either of those without great expense, I think
> a savings on primary-key lookups is not going to be adequate
> recompense.
I don't think it will be the default, but it would be a reasonable trade-off
for users who want IOTs, unless they often scan the whole table.
Regards,
---
Takahiro Itagaki
NTT Open Source Software Center
