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12.7.3. Read-ahead

Optimized loading in JBoss is called read-ahead. This refers to the technique of reading the row for an entity being loaded, as well as the next several rows; hence the term read-ahead. JBoss implements two main strategies (on-find and on-load) to optimize the loading problem identified in the previous section. The extra data loaded during read-ahead is not immediately associated with an entity object in memory, as entities are not materialized in JBoss until actually accessed. Instead, it is stored in the preload cache where it remains until it is loaded into an entity or the end of the transaction occurs. The following sections describe the read-ahead strategies.