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, the following features can stabilize query plans:
Optimizer hints
You can use pg_hint_plan to specify a query plan in each individual SQL statement.
Locked statistics
You can use pg_dbms_stats to lock statistical information per object, such as a database, schema, or table.
See
Refer to "Optimizer Hints" in the Application Development Guide for information on optimizer hints.
Refer to "Locked Statistics" in the Application Development Guide or information on locked statistics.
Note
Use the features provided when FUJITSU Enterprise Postgres is installed for optimizer hints and locked statistical information. FUJITSU Enterprise Postgres does not support other similar open-source features.