#include <DbXml.hpp>

XmlResults XmlQueryExpression::execute(
    XmlQueryContext &queryContext, u_int32_t flags = 0)
XmlResults XmlQueryExpression::execute(const XmlValue &contextItem,
    XmlQueryContext &queryContext, u_int32_t flags = 0)
XmlResults XmlQueryExpression::execute(
    XmlTransaction &txn, XmlQueryContext &queryContext, u_int32_t flags = 0)
XmlResults XmlQueryExpression::execute(XmlTransaction &txn,
    const XmlValue &contextItem, XmlQueryContext &queryContext, u_int32_t flags = 0)

Evaluates (runs) an XQuery query that was previously prepared by XmlManager::prepare and returns an XmlResults set.

There are two basic forms of this method: one that takes an XmlValue object, and another that does not. For methods that do not take an XmlValue, the XQuery must restrict the scope of the query using either the collection() or the doc() XQuery navigation functions, or an exception is thrown.

For those forms of this method that take an XmlValue, the query is applied against that object.

Evaluates the XQuery expression against the containers and documents identified by the query, from within the scope of the provided XmlTransaction object..

• If the operation is to be transaction-protected, the txn parameter is an XmlTransaction handle returned from XmlManager::createTransaction.

• The XmlQueryContext to use for this evaluation.

• The flags parameter must be set to 0 or by bitwise inclusively OR'ing together one or more of the following values:
  DB_READ_COMMITTED
  • This operation will have degree 2 isolation. This provides for cursor stability but not repeatable reads. Data items which have been previously read by this transaction may be deleted or modified by other transactions before this transaction completes.
  DB_READ_UNCOMMITTED
  • This operation will support degree 1 isolation; that is, read operations may return data that has been modified by other transactions but which has not yet been committed. Silently ignored if the DB_READ_UNCOMMITTED flag was not specified when the underlying container was opened.
  DB_RMW
  • Acquire write locks instead of read locks when doing the read, if locking is configured. Setting this flag can eliminate deadlock during a read-modify-write cycle by acquiring the write lock during the read part of the cycle so that another thread of control acquiring a read lock for the same item, in its own read-modify-write cycle, will not result in deadlock.
  DBXML_LAZY_DOCS
  • Retrieve the document lazily. That is, retrieve document content and document metadata only on an as needed basis when reading the document.
  DBXML_DOCUMENT_PROJECTION
  • When parsing a document in order to execute a query, use static analysis of the query to materialize only those portions of the document relevant to the query. This can significantly enhance performance of queries against documents from containers of type XmlContainer::WholedocContainer and documents not in a container. It should not be used if arbitrary navigation of the resulting nodes is to be performed, as not all nodes in the original document will be present and unexepcted results could be returned. This flag has no effect on documents in containers of type XmlContainer::NodeContainer.
  DBXML_WELL_FORMED_ONLY
  • Force the use of a scanner that will neither validate nor read schema or dtds associated with the document during parsing. This is efficient, but can cause parsing errors if the document references information that might have come from a schema or dtd, such as entity references.
  DBXML_NO_AUTO_COMMIT
  • Do not create and automatically commit a transaction if one is not provided to this method. A query that performs an update under a transactional environment will automatically be transaction protected unless this flag is specified. This flag is only necessary if the update will make changes to both transactional and non-transactional containers.
  
  

Evaluates the XQuery expression against the provided context item.

• The XmlTransaction object to use for this evaluation.

• The XmlValue object to perform the query against.

• The XmlQueryContext to use for this evaluation.

• The flags parameter must be set to 0 or by bitwise inclusively OR'ing together one or more of the following values:
  DB_READ_COMMITTED
  • This operation will have degree 2 isolation. This provides for cursor stability but not repeatable reads. Data items which have been previously read by this transaction may be deleted or modified by other transactions before this transaction completes.
  DB_READ_UNCOMMITTED
  • This operation will support degree 1 isolation; that is, read operations may return data that has been modified by other transactions but which has not yet been committed. Silently ignored if the DB_READ_UNCOMMITTED flag was not specified when the underlying container was opened.
  DB_RMW
  • Acquire write locks instead of read locks when doing the read, if locking is configured. Setting this flag can eliminate deadlock during a read-modify-write cycle by acquiring the write lock during the read part of the cycle so that another thread of control acquiring a read lock for the same item, in its own read-modify-write cycle, will not result in deadlock.
  DBXML_LAZY_DOCS
  • Retrieve the document lazily. That is, retrieve document content and document metadata only on an as needed basis when reading the document.
  DBXML_DOCUMENT_PROJECTION
  • When parsing a document in order to execute a query, use static analysis of the query to materialize only those portions of the document relevant to the query. This can significantly enhance performance of queries against documents from containers of type XmlContainer::WholedocContainer and documents not in a container. It should not be used if arbitrary navigation of the resulting nodes is to be performed, as not all nodes in the original document will be present and unexepcted results could be returned. This flag has no effect on documents in containers of type XmlContainer::NodeContainer.
  DBXML_WELL_FORMED_ONLY
  • Force the use of a scanner that will neither validate nor read schema or dtds associated with the document during parsing. This is efficient, but can cause parsing errors if the document references information that might have come from a schema or dtd, such as entity references.
  DBXML_NO_AUTO_COMMIT
  • Do not create and automatically commit a transaction if one is not provided to this method. A query that performs an update under a transactional environment will automatically be transaction protected unless this flag is specified. This flag is only necessary if the update will make changes to both transactional and non-transactional containers.
  
  

The XmlQueryExpression::execute method may fail and throw XmlException, encapsulating one of the following non-zero errors:

• Invalid flags to method XmlQueryExpression::execute