add a diagram
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@ -108,6 +108,8 @@ fundamental rule of thumb in ORM is:
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of a session/transaction, and fetch it immediately in one or two queries,
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of a session/transaction, and fetch it immediately in one or two queries,
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- and only then start navigating associations between persistent entities.
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- and only then start navigating associations between persistent entities.
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image:images/fetching.png[width=700,align="center"]
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Without question, the most common cause of poorly-performing data access
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Without question, the most common cause of poorly-performing data access
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code in Java programs is the problem of _N+1 selects_. Here, a list of N
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code in Java programs is the problem of _N+1 selects_. Here, a list of N
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rows is retrieved from the database in an initial query, and then
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rows is retrieved from the database in an initial query, and then
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