#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)

Description: XmlQueryExpression::execute

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.

Description: XmlQueryExpression.execute( XmlTransaction &txn, XmlQueryContext &queryContext, u_int32_t flags = 0)

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

Parameters

txn

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

queryContext

The XmlQueryContext to use for this evaluation.

flags

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 retrieval. 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_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.

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

Evaluates the XQuery expression against the provided context item.

Parameters

txn

The XmlTransaction object to use for this evaluation.

contextItem

The XmlValue object to perform the query against.

queryContext

The XmlQueryContext to use for this evaluation.

flags

The flags parameter must be set to 0 or by bitwise inclusively OR'ing together one or more of the following values:

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.

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 retrieval. 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.

Errors

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

INVALID_VALUE

Invalid flags to method XmlQueryExpression::execute