Dynamically Loading a Custom Filter

CDH 5.5 and higher adds (and enables by default) the ability to dynamically load a custom filter by adding a JAR with your filter to the directory specified by the hbase.dynamic.jars.dir property (which defaults to the lib/ directory under the HBase root directory).

To disable automatic loading of dynamic JARs, set hbase.use.dynamic.jars to false in the advanced configuration snippet for hbase-site.xml if you use Cloudera Manager, or to hbase-site.xml otherwise.

Filter Syntax Guidelines

HBase filters take zero or more arguments, in parentheses. Where the argument is a string, it is surrounded by single quotes ('string').

Logical Operators, Comparison Operators and Comparators

Filters can be combined together with logical operators. Some filters take a combination of comparison operators and comparators. Following is the list of each.

• AND - the key-value must pass both the filters to be included in the results.
• OR - the key-value must pass at least one of the filters to be included in the results.
• SKIP - for a particular row, if any of the key-values do not pass the filter condition, the entire row is skipped.
• WHILE - For a particular row, it continues to emit key-values until a key-value is reached that fails the filter condition.
• Compound Filters - Using these operators, a hierarchy of filters can be created. For example:

  (Filter1 AND Filter2)OR(Filter3 AND Filter4)

Comparison Operators

• LESS (<)
• LESS_OR_EQUAL (<=)
• EQUAL (=)
• NOT_EQUAL (!=)
• GREATER_OR_EQUAL (>=)
• GREATER (>)
• NO_OP (no operation)

Example1: >, 'binary:abc' will match everything that is lexicographically greater than "abc"
Example2: =, 'binaryprefix:abc' will match everything whose first 3 characters are lexicographically equal to "abc"
Example3: !=, 'regexstring:ab*yz' will match everything that doesn't begin with "ab" and ends with "yz"
Example4: =, 'substring:abc123' will match everything that begins with the substring "abc123"

Compound Operators

Within an expression, parentheses can be used to group clauses together, and parentheses have the highest order of precedence.

SKIP and WHILE operators are next, and have the same precedence.

The AND operator is next.

The OR operator is next.

A filter string of the form: “Filter1 AND Filter2 OR Filter3” will be evaluated as: “(Filter1 AND Filter2) OR Filter3”
A filter string of the form: “Filter1 AND SKIP Filter2 OR Filter3” will be evaluated as: “(Filter1 AND (SKIP Filter2)) OR Filter3”

Filter Types

HBase Shell Example

This example scans the 'users' table for rows where the contents of the cf:name column equals the string 'abc'.

hbase> scan 'users', { FILTER => SingleColumnValueFilter.new(Bytes.toBytes('cf'),
      Bytes.toBytes('name'), CompareFilter::CompareOp.valueOf('EQUAL'),
      BinaryComparator.new(Bytes.toBytes('abc')))}

Java API Example

This example, taken from the HBase unit test found in hbase-server/src/test/java/org/apache/hadoop/hbase/filter/TestSingleColumnValueFilter.java , shows how to use the Java API to implement several different filters..

/**
 *
 * 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.filter;

import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import java.util.regex.Pattern;

import org.apache.hadoop.hbase.KeyValue;
import org.apache.hadoop.hbase.SmallTests;
import org.apache.hadoop.hbase.filter.CompareFilter.CompareOp;
import org.apache.hadoop.hbase.util.Bytes;
import org.junit.Before;
import org.junit.Test;
import org.junit.experimental.categories.Category;

/**
 * Tests the value filter
 */
@Category(SmallTests.class)
public class TestSingleColumnValueFilter {
  private static final byte[] ROW = Bytes.toBytes("test");
  private static final byte[] COLUMN_FAMILY = Bytes.toBytes("test");
  private static final byte [] COLUMN_QUALIFIER = Bytes.toBytes("foo");
  private static final byte[] VAL_1 = Bytes.toBytes("a");
  private static final byte[] VAL_2 = Bytes.toBytes("ab");
  private static final byte[] VAL_3 = Bytes.toBytes("abc");
  private static final byte[] VAL_4 = Bytes.toBytes("abcd");
  private static final byte[] FULLSTRING_1 =
    Bytes.toBytes("The quick brown fox jumps over the lazy dog.");
  private static final byte[] FULLSTRING_2 =
    Bytes.toBytes("The slow grey fox trips over the lazy dog.");
  private static final String QUICK_SUBSTR = "quick";
  private static final String QUICK_REGEX = ".+quick.+";
  private static final Pattern QUICK_PATTERN = Pattern.compile("QuIcK", Pattern.CASE_INSENSITIVE | Pattern.DOTALL);

  Filter basicFilter;
  Filter nullFilter;
  Filter substrFilter;
  Filter regexFilter;
  Filter regexPatternFilter;

  @Before
  public void setUp() throws Exception {
    basicFilter = basicFilterNew();
    nullFilter = nullFilterNew();
    substrFilter = substrFilterNew();
    regexFilter = regexFilterNew();
    regexPatternFilter = regexFilterNew(QUICK_PATTERN);
  }

  private Filter basicFilterNew() {
    return new SingleColumnValueFilter(COLUMN_FAMILY, COLUMN_QUALIFIER,
      CompareOp.GREATER_OR_EQUAL, VAL_2);
  }

  private Filter nullFilterNew() {
    return new SingleColumnValueFilter(COLUMN_FAMILY, COLUMN_QUALIFIER, CompareOp.NOT_EQUAL,
        new NullComparator());
  }

  private Filter substrFilterNew() {
    return new SingleColumnValueFilter(COLUMN_FAMILY, COLUMN_QUALIFIER,
      CompareOp.EQUAL,
      new SubstringComparator(QUICK_SUBSTR));
  }

  private Filter regexFilterNew() {
    return new SingleColumnValueFilter(COLUMN_FAMILY, COLUMN_QUALIFIER,
      CompareOp.EQUAL,
      new RegexStringComparator(QUICK_REGEX));
  }

  private Filter regexFilterNew(Pattern pattern) {
    return new SingleColumnValueFilter(COLUMN_FAMILY, COLUMN_QUALIFIER,
        CompareOp.EQUAL,
        new RegexStringComparator(pattern.pattern(), pattern.flags()));
  }

  private void basicFilterTests(SingleColumnValueFilter filter)
      throws Exception {
    KeyValue kv = new KeyValue(ROW, COLUMN_FAMILY, COLUMN_QUALIFIER, VAL_2);
    assertTrue("basicFilter1", filter.filterKeyValue(kv) == Filter.ReturnCode.INCLUDE);
    kv = new KeyValue(ROW, COLUMN_FAMILY, COLUMN_QUALIFIER, VAL_3);
    assertTrue("basicFilter2", filter.filterKeyValue(kv) == Filter.ReturnCode.INCLUDE);
    kv = new KeyValue(ROW, COLUMN_FAMILY, COLUMN_QUALIFIER, VAL_4);
    assertTrue("basicFilter3", filter.filterKeyValue(kv) == Filter.ReturnCode.INCLUDE);
    assertFalse("basicFilterNotNull", filter.filterRow());
    filter.reset();
    kv = new KeyValue(ROW, COLUMN_FAMILY, COLUMN_QUALIFIER, VAL_1);
    assertTrue("basicFilter4", filter.filterKeyValue(kv) == Filter.ReturnCode.NEXT_ROW);
    kv = new KeyValue(ROW, COLUMN_FAMILY, COLUMN_QUALIFIER, VAL_2);
    assertTrue("basicFilter4", filter.filterKeyValue(kv) == Filter.ReturnCode.NEXT_ROW);
    assertFalse("basicFilterAllRemaining", filter.filterAllRemaining());
    assertTrue("basicFilterNotNull", filter.filterRow());
    filter.reset();
    filter.setLatestVersionOnly(false);
    kv = new KeyValue(ROW, COLUMN_FAMILY, COLUMN_QUALIFIER, VAL_1);
    assertTrue("basicFilter5", filter.filterKeyValue(kv) == Filter.ReturnCode.INCLUDE);
    kv = new KeyValue(ROW, COLUMN_FAMILY, COLUMN_QUALIFIER, VAL_2);
    assertTrue("basicFilter5", filter.filterKeyValue(kv) == Filter.ReturnCode.INCLUDE);
    assertFalse("basicFilterNotNull", filter.filterRow());
  }

  private void nullFilterTests(Filter filter) throws Exception {
    ((SingleColumnValueFilter) filter).setFilterIfMissing(true);
    KeyValue kv = new KeyValue(ROW, COLUMN_FAMILY, COLUMN_QUALIFIER, FULLSTRING_1);
    assertTrue("null1", filter.filterKeyValue(kv) == Filter.ReturnCode.INCLUDE);
    assertFalse("null1FilterRow", filter.filterRow());
    filter.reset();
    kv = new KeyValue(ROW, COLUMN_FAMILY, Bytes.toBytes("qual2"), FULLSTRING_2);
    assertTrue("null2", filter.filterKeyValue(kv) == Filter.ReturnCode.INCLUDE);
    assertTrue("null2FilterRow", filter.filterRow());
  }

  private void substrFilterTests(Filter filter)
      throws Exception {
    KeyValue kv = new KeyValue(ROW, COLUMN_FAMILY, COLUMN_QUALIFIER,
      FULLSTRING_1);
    assertTrue("substrTrue",
      filter.filterKeyValue(kv) == Filter.ReturnCode.INCLUDE);
    kv = new KeyValue(ROW, COLUMN_FAMILY, COLUMN_QUALIFIER,
      FULLSTRING_2);
    assertTrue("substrFalse", filter.filterKeyValue(kv) == Filter.ReturnCode.INCLUDE);
    assertFalse("substrFilterAllRemaining", filter.filterAllRemaining());
    assertFalse("substrFilterNotNull", filter.filterRow());
  }

  private void regexFilterTests(Filter filter)
      throws Exception {
    KeyValue kv = new KeyValue(ROW, COLUMN_FAMILY, COLUMN_QUALIFIER,
      FULLSTRING_1);
    assertTrue("regexTrue",
      filter.filterKeyValue(kv) == Filter.ReturnCode.INCLUDE);
    kv = new KeyValue(ROW, COLUMN_FAMILY, COLUMN_QUALIFIER,
      FULLSTRING_2);
    assertTrue("regexFalse", filter.filterKeyValue(kv) == Filter.ReturnCode.INCLUDE);
    assertFalse("regexFilterAllRemaining", filter.filterAllRemaining());
    assertFalse("regexFilterNotNull", filter.filterRow());
  }

  private void regexPatternFilterTests(Filter filter)
      throws Exception {
    KeyValue kv = new KeyValue(ROW, COLUMN_FAMILY, COLUMN_QUALIFIER,
      FULLSTRING_1);
    assertTrue("regexTrue",
      filter.filterKeyValue(kv) == Filter.ReturnCode.INCLUDE);
    assertFalse("regexFilterAllRemaining", filter.filterAllRemaining());
    assertFalse("regexFilterNotNull", filter.filterRow());
  }

  private Filter serializationTest(Filter filter)
      throws Exception {
    // Decompose filter to bytes.
    byte[] buffer = filter.toByteArray();

    // Recompose filter.
    Filter newFilter = SingleColumnValueFilter.parseFrom(buffer);
    return newFilter;
  }

  /**
   * Tests identification of the stop row
   * @throws Exception
   */
  @Test
  public void testStop() throws Exception {
    basicFilterTests((SingleColumnValueFilter) basicFilter);
    nullFilterTests(nullFilter);
    substrFilterTests(substrFilter);
    regexFilterTests(regexFilter);
    regexPatternFilterTests(regexPatternFilter);
  }

  /**
   * Tests serialization
   * @throws Exception
   */
  @Test
  public void testSerialization() throws Exception {
    Filter newFilter = serializationTest(basicFilter);
    basicFilterTests((SingleColumnValueFilter)newFilter);
    newFilter = serializationTest(nullFilter);
    nullFilterTests(newFilter);
    newFilter = serializationTest(substrFilter);
    substrFilterTests(newFilter);
    newFilter = serializationTest(regexFilter);
    regexFilterTests(newFilter);
    newFilter = serializationTest(regexPatternFilter);
    regexPatternFilterTests(newFilter);
  }

}