Extra single block read occurs on a query selecting just 1 row

[mroberts]

Here's another example where more rows are selected. Log file and iom trace
files can be found at srvalpha4:/home/wweeks/bug1846/OneBPP.

select p_partkey, p_size, p_retailprice from part where p_partkey in (
8380000,
16768608,
25157216,
33545824,
41934432,
50323040,
58711648,
67100256,
75488864,
83877472,
92266080,
100654688,
109043296,
117431904,
125820512,
134209120,
142597728,
150986336,
159374944,
167763552,
176152160,
184540768,
192929376
);

The p_retailprice column is doing the extra single block reads. There are 23
rows, so there shouldn't be more than 23 reads.
[root@srvalpha4 runWith16BPPInstances]# grep "3539 " iom* | awk '{reads+=1;
ttl+=
$6; print $1 " " $6}END{print "Reads="reads "; Total="ttl}'
iom.1115699520:3539 1
iom.1115699520:3539 1
iom.1115699520:3539 1
iom.1115699520:3539 1
iom.1115699520:3539 512
iom.1126189376:3539 512
iom.1126189376:3539 1
iom.1126189376:3539 1
iom.1126189376:3539 512
iom.1126189376:3539 1
iom.1136679232:3539 512
iom.1136679232:3539 512
iom.1136679232:3539 512
iom.1147169088:3539 512
iom.1147169088:3539 512
iom.1147169088:3539 1
iom.1157658944:3539 1
iom.1157658944:3539 512
iom.1168148800:3539 1
iom.1178638656:3539 1
iom.1189128512:3539 1
iom.1189128512:3539 1
iom.1199618368:3539 512
iom.1220598080:3539 512
iom.1220598080:3539 512
iom.1231087936:3539 512
iom.1231087936:3539 1
iom.1231087936:3539 1
iom.1252067648:3539 1
iom.1252067648:3539 512
iom.1262557504:3539 512
Reads=31; Total=7696

The p_size reads look right. 23 total reads for the 23 rows.
p_size reads (oid 3537):
[root@srvalpha4 runWith16BPPInstances]# grep "3537 " iom* | awk '{reads+=1;
ttl+=$6; print $1 " " $6}END{print "Reads="reads "; Total="ttl}'
iom.1105209664:3537 512
iom.1115699520:3537 512
iom.1115699520:3537 1
iom.1126189376:3537 1
iom.1136679232:3537 1
iom.1136679232:3537 512
iom.1147169088:3537 512
iom.1147169088:3537 1
iom.1157658944:3537 512
iom.1157658944:3537 512
iom.1168148800:3537 1
iom.1199618368:3537 1
iom.1199618368:3537 512
iom.1210108224:3537 512
iom.1210108224:3537 1
iom.1210108224:3537 512
iom.1210108224:3537 512
iom.1220598080:3537 1
iom.1241577792:3537 512
iom.1241577792:3537 512
iom.1252067648:3537 512
iom.1252067648:3537 512
iom.1262557504:3537 512
Reads=23; Total=7688