SingleColumnValueFilter

/*
 * Copyright (c) 2011.  The Apache Software Foundation
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.hadoop.hbase.hbql.filter;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.KeyValue;
import org.apache.hadoop.hbase.filter.BinaryComparator;
import org.apache.hadoop.hbase.filter.CompareFilter;
import org.apache.hadoop.hbase.filter.WritableByteArrayComparable;
import org.apache.hadoop.hbase.io.HbaseObjectWritable;
import org.apache.hadoop.hbase.util.Bytes;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.Arrays;


/**
 * This filter is used to filter cells based on value. It takes a
 * {@link org.apache.hadoop.hbase.filter.CompareFilter.CompareOp}
 * operator (equal, greater, not equal, etc), and either a byte [] value or
 * a {@link org.apache.hadoop.hbase.filter.WritableByteArrayComparable}.
 * <p/>
 * If we have a byte [] value then we just do a lexicographic compare. For
 * example, if passed value is 'b' and cell has 'a' and the compare operator
 * is LESS, then we will filter out this cell (return true).  If this is not
 * sufficient (eg you want to deserialize a long and then compare it to a fixed
 * long value), then you can pass in your own comparator instead.
 * <p/>
 * You must also specify a family and qualifier.  Only the value of this column
 * will be tested.
 * <p/>
 * To prevent the entire row from being emitted if the column is not found
 * on a row, use {@link #setFilterIfMissing}.
 * Otherwise, if the column is found, the entire row will be emitted only if
 * the value passes.  If the value fails, the row will be filtered out.
 * <p/>
 * In order to test values of previous versions (timestamps), set
 * {@link #setLatestVersionOnly} to false. The default is true, meaning that
 * only the latest version's value is tested and all previous versions are ignored.
 * <p/>
 * To filter based on the value of all scanned columns, use {@link org.apache.hadoop.hbase.filter.ValueFilter}.
 */
public class SingleColumnValueFilter extends InstrumentedFilter {
    static final Log LOG = LogFactory.getLog(SingleColumnValueFilter.class);

    private boolean verbose = false;
    private byte[]                      columnFamily;
    private byte[]                      columnQualifier;
    private CompareFilter.CompareOp     compareOp;
    private WritableByteArrayComparable comparator;
    private boolean foundColumn       = false;
    private boolean matchedColumn     = false;
    private boolean filterIfMissing   = false;
    private boolean latestVersionOnly = true;

    /**
     * Writable constructor, do not use.
     */
    public SingleColumnValueFilter() {
    }

    /**
     * Constructor for binary compare of the value of a single column.  If the
     * column is found and the condition passes, all columns of the row will be
     * emitted.  If the column is not found or the condition fails, the row will
     * not be emitted.
     *
     * @param family    name of column family
     * @param qualifier name of column qualifier
     * @param compareOp operator
     * @param value     value to compare column values against
     */
    public SingleColumnValueFilter(final byte[] family, final byte[] qualifier,
                                   final CompareFilter.CompareOp compareOp, final byte[] value) {
        this(family, qualifier, compareOp, new BinaryComparator(value));
    }

    /**
     * Constructor for binary compare of the value of a single column.  If the
     * column is found and the condition passes, all columns of the row will be
     * emitted.  If the condition fails, the row will not be emitted.
     * <p/>
     * Use the filterIfColumnMissing flag to set whether the rest of the columns
     * in a row will be emitted if the specified column to check is not found in
     * the row.
     *
     * @param family     name of column family
     * @param qualifier  name of column qualifier
     * @param compareOp  operator
     * @param comparator Comparator to use.
     */
    public SingleColumnValueFilter(final byte[] family, final byte[] qualifier,
                                   final CompareFilter.CompareOp compareOp, final WritableByteArrayComparable comparator) {
        this.columnFamily = family;
        this.columnQualifier = qualifier;
        this.compareOp = compareOp;
        this.comparator = comparator;
    }

    public void setVerbose(final boolean verbose) {
        this.verbose = verbose;
    }

    public boolean getVerbose() {
        return this.verbose;
    }

    public boolean filterRowKey(byte[] rowKey, int offset, int length) {
        // We don't filter on the row key... we filter later on column value so
        // always return false.
        return false;
    }

    public ReturnCode filterKeyValue(KeyValue keyValue) {
        // System.out.println("REMOVE KEY=" + keyValue.toString() + ", value=" + Bytes.toString(keyValue.getValue()));
        if (this.matchedColumn) {
            // We already found and matched the single column, all keys now pass
            return ReturnCode.INCLUDE;
        }
        else if (this.latestVersionOnly && this.foundColumn) {
            // We found but did not match the single column, skip to next row
            return ReturnCode.NEXT_ROW;
        }
        if (!keyValue.matchingColumn(this.columnFamily, this.columnQualifier)) {
            return ReturnCode.INCLUDE;
        }
        foundColumn = true;
        if (filterColumnValue(keyValue.getBuffer(),
                              keyValue.getValueOffset(), keyValue.getValueLength())) {
            return this.latestVersionOnly ? ReturnCode.NEXT_ROW : ReturnCode.INCLUDE;
        }
        this.matchedColumn = true;
        return ReturnCode.INCLUDE;
    }

    private boolean filterColumnValue(final byte[] data, final int offset,
                                      final int length) {
        // TODO: Can this filter take a rawcomparator so don't have to make this
        // byte array copy?
        int compareResult = this.comparator.compareTo(Arrays.copyOfRange(data, offset, offset + length));

        if (this.getVerbose())
            LOG.debug("compareResult=" + compareResult + " " + Bytes.toString(data, offset, length));

        switch (this.compareOp) {
            case LESS:
                return compareResult <= 0;
            case LESS_OR_EQUAL:
                return compareResult < 0;
            case EQUAL:
                return compareResult != 0;
            case NOT_EQUAL:
                return compareResult == 0;
            case GREATER_OR_EQUAL:
                return compareResult > 0;
            case GREATER:
                return compareResult >= 0;
            default:
                throw new RuntimeException("Unknown Compare op " + compareOp.name());
        }
    }

    public boolean filterAllRemaining() {
        return false;
    }

    public boolean filterRow() {
        // If column was found, return false if it was matched, true if it was not
        // If column not found, return true if we filter if missing, false if not
        return this.foundColumn ? !this.matchedColumn : this.filterIfMissing;
    }

    public void reset() {
        foundColumn = false;
        matchedColumn = false;
    }

    /**
     * Get whether entire row should be filtered if column is not found.
     *
     * @return true if row should be skipped if column not found, false if row
     *         should be let through anyways
     */
    public boolean getFilterIfMissing() {
        return filterIfMissing;
    }

    /**
     * Set whether entire row should be filtered if column is not found.
     * <p/>
     * If true, the entire row will be skipped if the column is not found.
     * <p/>
     * If false, the row will pass if the column is not found.  This is default.
     */
    public void setFilterIfMissing(boolean filterIfMissing) {
        this.filterIfMissing = filterIfMissing;
    }

    /**
     * Get whether only the latest version of the column value should be compared.
     * If true, the row will be returned if only the latest version of the column
     * value matches. If false, the row will be returned if any version of the
     * column value matches. The default is true.
     */
    public boolean getLatestVersionOnly() {
        return latestVersionOnly;
    }

    /**
     * Set whether only the latest version of the column value should be compared.
     * If true, the row will be returned if only the latest version of the column
     * value matches. If false, the row will be returned if any version of the
     * column value matches. The default is true.
     */
    public void setLatestVersionOnly(boolean latestVersionOnly) {
        this.latestVersionOnly = latestVersionOnly;
    }

    public void readFields(final DataInput in) throws IOException {

        this.verbose = in.readBoolean();

        this.columnFamily = Bytes.readByteArray(in);
        if (this.columnFamily.length == 0) {
            this.columnFamily = null;
        }
        this.columnQualifier = Bytes.readByteArray(in);
        if (this.columnQualifier.length == 0) {
            this.columnQualifier = null;
        }
        this.compareOp = CompareFilter.CompareOp.valueOf(in.readUTF());
        this.comparator =
                (WritableByteArrayComparable)HbaseObjectWritable.readObject(in, null);
        this.foundColumn = in.readBoolean();
        this.matchedColumn = in.readBoolean();
        this.filterIfMissing = in.readBoolean();
        this.latestVersionOnly = in.readBoolean();
    }

    public void write(final DataOutput out) throws IOException {

        out.writeBoolean(this.getVerbose());

        Bytes.writeByteArray(out, this.columnFamily);
        Bytes.writeByteArray(out, this.columnQualifier);
        out.writeUTF(compareOp.name());
        HbaseObjectWritable.writeObject(out, comparator,
                                        WritableByteArrayComparable.class, null);
        out.writeBoolean(foundColumn);
        out.writeBoolean(matchedColumn);
        out.writeBoolean(filterIfMissing);
        out.writeBoolean(latestVersionOnly);
    }
}