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What Is Query Rewrite?

April 26, 2017query rewrite

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What Is Query Rewrite?

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When the XMLType is stored in structured storage (object-relationally) using an XML schema and queries using XPath are used, they are rewritten to go directly to the underlying object-relational columns. This enables the use of B*Tree or other indexes, if present on the column, to be used in query evaluation by the Optimizer. This query rewrite mechanism is used for XPaths in SQL functions such as existsNode(), extract(), extractValue(), and updateXML(). This enables the XPath to be evaluated against the XML document without having to ever construct the XML document in memory.