> > And, while we are on heap subject - using index (RECNO) for heap
> > means that all our secondary-index scans will performe TWO
> > index scans - first, to find recno in secondary-index, and
> > second, to find heap tuple using recno (now indices give us
> > TID, which is physical address).
> 
> Yes, that was one of my questions.  Why use recno at all?  We already
> have heap access which is very fast.  Why switch to SDB which gives us
> a recno ordering of heap that doesn't do us any real good, except to
> allow tuple update without changing indexes.

But if we'll use our heap AM, then we'll have to implement redo/undo
for it... no sence to switch to SDB for btree/hash WAL support -:)

Vadim

Sun, 21 May 2000 20:00:01 -0700
"Mikheev, Vadim" <vmikheev@SECTORBASE.COM>
RE: Berkeley DB...
[Charset iso-8859-1 unsupported, filtering to ASCII...]
> > > And, while we are on heap subject - using index (RECNO) for heap
> > > means that all our secondary-index scans will performe TWO
> > > index scans - first, to find recno in secondary-index, and
> > > second, to find heap tuple using recno (now indices give us
> > > TID, which is physical address).
> > 
> > Yes, that was one of my questions.  Why use recno at all?  We already
> > have heap access which is very fast.  Why switch to SDB which gives us
> > a recno ordering of heap that doesn't do us any real good, except to
> > allow tuple update without changing indexes.
> 
> But if we'll use our heap AM, then we'll have to implement redo/undo
> for it... no sence to switch to SDB for btree/hash WAL support -:)

Yes, SDB would give us redo/undo in heap, and that would make things
easier.  However, if there is the overhead of a double-index lookup when
using indexes, it seems like a very high cost.

-- 
  Bruce Momjian                        |  http://www.op.net/~candle
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

Sun, 21 May 2000 23:11:00 -0400 (EDT)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: Berkeley DB...