Fujitsu Enterprise Postgres estimates the cost of query plans based on SQL statements and database statistical information, and selects the least expensive query plan. However, like other databases, Fujitsu Enterprise Postgres does not necessarily select the most suitable query plan. For example, it may suddenly select unsuitable query plan due to changes in the data conditions.
In mission-critical systems, stable performance is more important than improved performance, and changes in query plans case to be avoided. In this situation, pg_hint_plan and pg_dbms_stats can be used to stabilize the query plan.
See
Refer to "Enhanced query plan stability" in the Operation Guide for information on enhanced query plan stability.
Note
For pg_hint_plan and pg_dbms_stats, take advantage of features introduced when installing Fujitsu Enterprise Postgres. Fujitsu Enterprise Postgres does not support other similar open-source features.
