I know you will shoot me down, but... Why is there an entry in the index for a row if the row is not valid? Wouldn't it be better for the index entry validity to track the row validity. If a particular data value for a query (join, where etc.) can be satisfied by the index entry itself this would be a big performance gain.
Cheers, Gary. On 28 Apr 2004 at 0:27, Tom Lane wrote: > [EMAIL PROTECTED] writes: > > ... Wouldn't the most efficient plan be to scan the index regardless > > of crm_id because the only columns needed are in the index? > > No. People coming from other databases often have the misconception > that queries can be answered by looking only at an index. That is never > true in Postgres because row validity info is only stored in the table; > so we must always visit the table entry to make sure the row is still > valid/visible for the current query. > > Accordingly, columns added to the index that aren't constrained by the > WHERE clause are not very useful ... > > regards, tom lane > > ---------------------------(end of broadcast)--------------------------- > TIP 8: explain analyze is your friend ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
