/**
* (c) Copyright 2012 WibiData, Inc.
*
* See the NOTICE file distributed with this work for additional
* information regarding copyright ownership.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.kiji.schema.impl;
import java.io.IOException;
import com.google.common.base.Objects;
import com.google.common.base.Preconditions;
import org.apache.hadoop.hbase.filter.ColumnPaginationFilter;
import org.apache.hadoop.hbase.filter.Filter;
import org.apache.hadoop.hbase.filter.FilterList;
import org.kiji.annotations.ApiAudience;
import org.kiji.schema.KijiColumnName;
import org.kiji.schema.filter.KijiColumnFilter;
/**
* A KijiColumnFilter that allows for pagination over the qualifiers in a row, along with
* other filters that are and-ed together.
*
* <p>Note that starting in HBase 0.94, this will only return at most one value, regardless
* of where maxVersions is set to (because the HBase Filter return code is set to
* INCLUDE_AND_NEXT_COL semantics). Because of this, we have enforced a lack of options
* regarding maxVersions for this filter.</p>
*
* <p>This should only be used internally e.g. in HBaseQualifierPager to retrieve qualifiers
* or other single-valued output.</p>
*/
@ApiAudience.Private
public final class KijiPaginationFilter extends KijiColumnFilter {
private static final long serialVersionUID = 1L;
/** The max number of qualifiers to return. */
private final int mMaxQualifiers;
/** How many versions back in history to start looking. */
private final int mOffset = 0;
/** Other filters to be checked before the pagination filter. */
private final KijiColumnFilter mInputFilter;
/**
* Initialize pagination filter with default settings.
*
* @param maxQualifiers Maximum number of qualifiers to return. Must be >= 1.
*/
public KijiPaginationFilter(int maxQualifiers) {
Preconditions.checkArgument(maxQualifiers >= 1,
"Invalid maximum number of qualifiers to return: %s", maxQualifiers);
mInputFilter = null;
mMaxQualifiers = maxQualifiers;
}
/**
* Initialize pagination filter with other filters to fold in.
*
* @param filter Other filter that will precede
* @param maxQualifiers Maximum number of qualifiers to return. Must be >= 1.
*/
public KijiPaginationFilter(KijiColumnFilter filter, int maxQualifiers) {
Preconditions.checkArgument(maxQualifiers >= 1,
"Invalid maximum number of qualifiers to return: %s", maxQualifiers);
mInputFilter = filter;
mMaxQualifiers = maxQualifiers;
}
/** {@inheritDoc} */
@Override
public Filter toHBaseFilter(KijiColumnName kijiColumnName, Context context) throws IOException {
FilterList requestFilter = new FilterList(FilterList.Operator.MUST_PASS_ALL);
// Order that filters get added matters. Earlier in the list, the higher priority.
if (mInputFilter != null) {
requestFilter.addFilter(mInputFilter.toHBaseFilter(kijiColumnName, context));
}
Filter paginationFilter = new ColumnPaginationFilter(mMaxQualifiers, mOffset);
requestFilter.addFilter(paginationFilter);
return requestFilter;
}
/** {@inheritDoc} */
@Override
public boolean equals(Object other) {
if (!(other instanceof KijiPaginationFilter)) {
return false;
} else {
final KijiPaginationFilter otherFilter = (KijiPaginationFilter) other;
return Objects.equal(otherFilter.mMaxQualifiers, mMaxQualifiers)
&& Objects.equal(otherFilter.mOffset, mOffset)
&& Objects.equal(otherFilter.mInputFilter, mInputFilter);
}
}
/** {@inheritDoc} */
@Override
public int hashCode() {
return Objects.hashCode(mMaxQualifiers, mOffset, mInputFilter);
}
/** {@inheritDoc} */
@Override
public String toString() {
return Objects.toStringHelper(KijiPaginationFilter.class)
.add("max-qualifiers", mMaxQualifiers)
.add("offset", mOffset)
.add("filter", mInputFilter)
.toString();
}
}