materialized views

Es ist ein bekanntes Problem, dass das Ändern der Storage Engine von MyISAM nach InnoDB Probleme verursachen kann [ 1 ], wenn Abfragen der folgenden Art auftreten:

SELECT COUNT(*) from table;

Glücklicherweise kommt dieser Typ von Abfragen selten vor. Und wenn, kann die Abfrage meist einfach weggelassen oder darum herum gearbeitet werden, indem man die Anzahl Zeilen in der Tabelle schätzt. Zum Beispiel mit:

Its a known problem that changing the Storage Engine from MyISAM to InnoDB can cause some problems [ 1 ] if you have queries of this type:

SELECT COUNT(*) from table;

Luckily this query happens rarely and if, the query can be easily omitted or worked around by guesstimating the amount of rows in the table. For example with:

Materialised View (MV) is the pre-calculated (materialised) result of a query. Unlike a simple VIEW the result of a Materialised View is stored somewhere, generally in a table. Materialised Views are used when immediate response is needed and the query where the Materialised View bases on would take to long to produce a result. Materialised Views have to be refreshed once in a while. It depends on the requirements how often a Materialised View is refreshed and how actual its content is.