| /* |
| * Copyright (C) 2014 The Async HBase Authors. All rights reserved. |
| * This file is part of Async HBase. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are met: |
| * - Redistributions of source code must retain the above copyright notice, |
| * this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright notice, |
| * this list of conditions and the following disclaimer in the documentation |
| * and/or other materials provided with the distribution. |
| * - Neither the name of the StumbleUpon nor the names of its contributors |
| * may be used to endorse or promote products derived from this software |
| * without specific prior written permission. |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
| * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE |
| * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| * POSSIBILITY OF SUCH DAMAGE. |
| */ |
| package org.hbase.async; |
| |
| import java.lang.UnsupportedOperationException; |
| |
| import org.jboss.netty.buffer.ChannelBuffer; |
| import org.hbase.async.generated.FilterPB; |
| |
| /** |
| * A filter, based on the ColumnCountGetFilter, takes two arguments: limit and offset. |
| * This filter can be used for row-based indexing, where references to other tables are |
| * stored across many columns, in order to efficient lookups and paginated results for |
| * end users. Only most recent versions are considered for pagination. |
| */ |
| public final class ColumnPaginationFilter extends ScanFilter { |
| private static final byte[] NAME = Bytes.UTF8("org.apache.hadoop" |
| + ".hbase.filter.ColumnPaginationFilter"); |
| |
| private int limit = 0; |
| private int offset = -1; |
| private byte[] columnOffset = null; |
| |
| /** |
| * Initializes filter with an integer offset and limit. The offset is arrived at |
| * scanning sequentially and skipping entries. @limit number of columns are |
| * then retrieved. If multiple column families are involved, the columns may be spread |
| * across them. |
| * |
| * @param limit Max number of columns to return. |
| * @param offset The integer offset where to start pagination. |
| */ |
| public ColumnPaginationFilter(final int limit, final int offset) { |
| this.limit = limit; |
| this.offset = offset; |
| } |
| |
| /** |
| * Initializes filter with a string/bookmark based offset and limit. The offset is arrived |
| * at, by seeking to it using scanner hints. If multiple column families are involved, |
| * pagination starts at the first column family which contains @columnOffset. Columns are |
| * then retrieved sequentially up to @limit number of columns which maybe spread across |
| * multiple column families, depending on how the scan is setup. |
| * |
| * Only supported with HBase 0.96 and greater. |
| * |
| * @param limit Max number of columns to return. |
| * @param columnOffset The string/bookmark offset on where to start pagination. |
| */ |
| public ColumnPaginationFilter(final int limit, final byte[] columnOffset) { |
| this.limit = limit; |
| this.columnOffset = columnOffset; |
| } |
| |
| public ColumnPaginationFilter(final int limit, final String columnOffset) { |
| this.limit = limit; |
| this.columnOffset = Bytes.UTF8(columnOffset); |
| } |
| |
| @Override |
| byte[] serialize() { |
| FilterPB.ColumnPaginationFilter.Builder builder = |
| FilterPB.ColumnPaginationFilter.newBuilder(); |
| builder.setLimit(this.limit); |
| if (this.offset >= 0) { |
| builder.setOffset(this.offset); |
| } |
| if (this.columnOffset != null) { |
| builder.setColumnOffset(Bytes.wrap(this.columnOffset)); |
| } |
| return builder.build().toByteArray(); |
| } |
| |
| @Override |
| byte[] name() { |
| return NAME; |
| } |
| |
| @Override |
| int predictSerializedSize() { |
| int size = 1 + NAME.length |
| + 3 + (columnOffset == null ? 0 : columnOffset.length) |
| + 4 //limit |
| + 4; //offset |
| return size; |
| } |
| |
| @Override |
| void serializeOld(final ChannelBuffer buf) { |
| buf.writeByte((byte) NAME.length); // 1 |
| buf.writeBytes(NAME); // 53 |
| buf.writeInt(limit); // 4 |
| buf.writeInt(offset); // 4 |
| if (columnOffset != null) { |
| //Setting a columnOffset is not supported before HBase 0.96 |
| throw new UnsupportedOperationException( |
| "Setting a column offset by byte array is not supported before HBase 0.96"); |
| } |
| } |
| |
| @Override |
| public String toString() { |
| if (this.columnOffset != null) { |
| return (this.getClass().getSimpleName() + "(" + this.limit + ", " + |
| Bytes.pretty(this.columnOffset) + ")"); |
| } |
| return String.format("%s (%d, %d): predict:%d serialize:%d %s", this.getClass().getSimpleName(), |
| this.limit, this.offset, predictSerializedSize(), serialize().length, Bytes.pretty(serialize())); |
| } |
| |
| } |