Re: possible TODO: read-only tables, select from indexes only.

Bruce Momjian wrote:
> See this TODO: * Allow data to be pulled directly from indexes
> I think this is the direction we should be heading because it has more
> general usefulness.

I think read-only tables would have a few different types
of general usefulness in addition to enabling index scans.

Is this a fair summary of the potential benefits of READ-ONLY
tables? (from both this thread and the archives):

1. Index-only scans are made possible fairly easily because
you wouldn't need to check the heap for visibility.

2. Simple tables can be much smaller since you don't need
most of the HeapTupleHeaderData. This reduction in
space translates to a reduction in I/O through better
use of the shared memory and OS caches.

3. A Read-Only Clustered table could be assumed to be
sorted, so you could avoid some Sort steps
for things like GroupAggregates and Merge Joins.

Any others?

The biggest/slowest tables in my database happen to be
entirely read only (road network and other GIS features
for the country; and data warehouse tables representing
previous quarter's data).