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SQL Anywhere 10.0.1 » SQL Anywhere Server - SQL Usage » Monitoring and Improving Performance » Performance improvement tips

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Choose the optimizer priority

The optimization_goal option controls whether SQL Anywhere optimizes SQL statements for response time (First-row) or for total resource consumption (All-rows). In simpler terms, you can pick whether to optimize query processing towards returning the first row quickly, or towards minimizing the cost of returning the complete result set.

If the option is set to First-row, SQL Anywhere chooses an access plan that is intended to reduce the time to fetch the first row of the query's result, possibly at the expense of total retrieval time. In particular, the optimizer typically avoids, if possible, access plans that require the materialization of results to reduce the time to return the first row. With this setting, for example, the optimizer favors access plans that utilize an index to satisfy a query's ORDER BY clause, rather than plans that require an explicit sorting operation.

You can use the FASTFIRSTROW table hint in a query's FROM clause to set the optimization goal for a specific query to First-row, without having to change the optimization_goal setting.

If the option is set to All-rows (the default), then SQL Anywhere optimizes a query so as to choose an access plan with the minimal estimated total retrieval time. Setting optimization_goal to All-rows may be appropriate for applications that intend to process the entire result set, such as PowerBuilder DataWindow applications.

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