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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 2009, 2015 Oracle and/or its affiliates. All rights reserved.
*
*/
using System;
using System.Collections.Generic;
using System.Text;
using BerkeleyDB.Internal;
namespace BerkeleyDB {
/// <summary>
/// A class representing configuration parameters for <see cref="Cursor"/>
/// </summary>
public class CursorConfig {
/// <summary>
/// The isolation degree that the cursor should use.
/// </summary>
/// <remarks>
/// <para>
/// <see cref="Isolation.DEGREE_TWO"/> ensures the stability of the
/// current data item read by this cursor but permits data read by this
/// cursor to be modified or deleted prior to the commit of the
/// transaction for this cursor.
/// </para>
/// <para>
/// <see cref="Isolation.DEGREE_ONE"/> allows read operations performed
/// by the cursor to return modified but not yet committed data.
/// Silently ignored if the <see cref="DatabaseConfig.ReadUncommitted"/>
/// was not specified when the underlying database was opened.
/// </para>
/// </remarks>
public Isolation IsolationDegree;
/// <summary>
/// If true, specify that the cursor is used to update the
/// database. The underlying database environment must have been opened
/// with <see cref="DatabaseEnvironmentConfig.UseCDB"/> set.
/// </summary>
public bool WriteCursor;
/// <summary>
/// <para>
/// Configure a transactional cursor to operate with read-only snapshot
/// isolation. For databases with <see cref="DatabaseConfig.UseMVCC"/>
/// set, data values are read as they are when the cursor is opened,
/// without taking read locks.
/// </para>
/// <para>
/// This setting implicitly begins a transaction that is committed when
/// the cursor is closed.
/// </para>
/// <para>
/// This setting is silently ignored if
/// <see cref="DatabaseConfig.UseMVCC"/> is not set on the underlying
/// database or if a transaction is supplied to
/// <see cref="BaseDatabase.Cursor"/>
/// </para>
/// </summary>
public bool SnapshotIsolation;
/// <summary>
/// The cache priority for pages referenced by the cursor.
/// </summary>
/// <remarks>
/// The priority of a page biases the replacement algorithm to be more
/// or less likely to discard a page when space is needed in the buffer
/// pool. The bias is temporary, and pages are eventually discarded
/// if they are not referenced again. The setting is only advisory, and
/// does not guarantee pages will be treated in a specific way.
/// </remarks>
public CachePriority Priority;
/// <summary>
/// Instantiate a new CursorConfig object
/// </summary>
public CursorConfig() {
IsolationDegree = Isolation.DEGREE_THREE;
Priority = CachePriority.DEFAULT;
}
internal uint flags {
get {
uint ret = 0;
ret |= (IsolationDegree == Isolation.DEGREE_ONE)
? DbConstants.DB_READ_UNCOMMITTED : 0;
ret |= (IsolationDegree == Isolation.DEGREE_TWO)
? DbConstants.DB_READ_COMMITTED : 0;
ret |= (WriteCursor) ? DbConstants.DB_WRITECURSOR : 0;
ret |= (SnapshotIsolation) ? DbConstants.DB_TXN_SNAPSHOT : 0;
return ret;
}
}
}
}
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