[PERFORM] Performance degradation from PostgreSQL 8.2.21 to PostgreSQL 9.3.2 - Mailing list pgsql-performance

Issuing exactly the same query as PostgreSQL 8.2.21 and PostgreSQL 9.3.2 will slow the response by 6.4 ms on average.
What could be the cause?
Measurement method is as follows.
・ PostgreSQL 8.2.21 installation
 ★Measurement
・ Export DUMP of PostgreSQL 8.2.21
・ PostgreSQL 8.2.21 uninstallation
・ PostgreSQL 9.3.2 installation
・ Dump import
 ★Measurement

[query]
select
 table4.a as col_0_0_,
 table4.a as col_1_0_,
 table4.a as col_2_0_,
 table4.b as col_0_1_,
 table4.c,
 table4.d
from
 table1,
 table2,
 table3,
 table4
where
 table1.a=table2.a and
 table1.a="parameter$1" and
 table2.roleid=table3.roleid and
 table3.a="parameter$2" and
 table4.b='3' and
 table2.a=table4.a;