com.pingcap.tikv.expression.visitor.IndexRangeSetBuilder Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of tikv-client Show documentation
There is a newer version: 3.2.3
/*
 * Copyright 2017 PingCAP, Inc.
 *
 * 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,
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.pingcap.tikv.expression.visitor;

import com.google.common.collect.Range;
import com.google.common.collect.RangeSet;
import com.google.common.collect.TreeRangeSet;
import com.pingcap.tikv.expression.ColumnRef;
import com.pingcap.tikv.expression.ComparisonBinaryExpression;
import com.pingcap.tikv.expression.ComparisonBinaryExpression.NormalizedPredicate;
import com.pingcap.tikv.expression.StringRegExpression;
import com.pingcap.tikv.key.TypedKey;
import com.pingcap.tikv.meta.TiIndexColumn;
import com.pingcap.tikv.meta.TiIndexInfo;
import com.pingcap.tikv.meta.TiTableInfo;
import com.pingcap.tikv.types.DataType;
import java.util.HashMap;
import java.util.Map;

public class IndexRangeSetBuilder extends RangeSetBuilder {

  private final Map lengths; // length of corresponding ColumnRef

  public IndexRangeSetBuilder(TiTableInfo table, TiIndexInfo index) {
    Map result = new HashMap<>();
    if (table != null && index != null) {
      for (TiIndexColumn indexColumn : index.getIndexColumns()) {
        ColumnRef columnRef = ColumnRef.create(indexColumn.getName(), table);
        result.put(columnRef, (int) indexColumn.getLength());
      }
    }
    this.lengths = result;
  }

  @Override
  protected RangeSet visit(ComparisonBinaryExpression node, Void context) {
    NormalizedPredicate predicate = node.normalize();
    if (predicate == null) {
      throwOnError(node);
    }
    // In order to match a prefix index, we have to cut the literal by prefix length.
    // e.g., for table t:
    // CREATE TABLE `t` {
    //     `b` VARCHAR(10) DEFAULT NULL,
    //     KEY `prefix_index` (`b`(2))
    // }
    //
    // b(2) > "bbc" -> ["bb", +∞)
    // b(2) >= "bbc" -> ["bb", +∞)
    // b(2) < "bbc" -> (-∞, "bb"]
    // b(2) <= "bbc" -> (-∞, "bb"]
    // b(2) = "bbc" -> ["bb", "bb"]
    // b(2) > "b" -> ["b", +∞)
    // b(2) >= "b" -> ["b", +∞)
    // b(2) < "b" -> (-∞, "b"]
    // b(2) <= "b" -> (-∞, "b"]
    //
    // For varchar, `b`(2) will take first two characters(bytes) as prefix index.
    // TODO: Note that TiDB only supports UTF-8, we need to check if prefix index behave differently
    // under other encoding methods
    int prefixLen = lengths.getOrDefault(predicate.getColumnRef(), DataType.UNSPECIFIED_LEN);
    TypedKey literal = predicate.getTypedLiteral(prefixLen);
    boolean loose = !DataType.isLengthUnSpecified(prefixLen);
    // With prefix length specified, the filter is loosen and so should the ranges
    return visitComparisonBinaryExpr(node, context, literal, loose);
  }

  @Override
  protected RangeSet visit(StringRegExpression node, Void context) {
    ColumnRef columnRef = node.getColumnRef();
    // In order to match a prefix index, we have to cut the literal by prefix length.
    // e.g., for table t:
    // CREATE TABLE `t` {
    //     `c1` VARCHAR(10) DEFAULT NULL,
    //     KEY `prefix_index` (`c`(2))
    // }
    // when the predicate is `c1` LIKE 'abc%', the index range should be ['ab', 'ab'].
    // when the predicate is `c1` LIKE 'a%', the index range should be ['a', 'b').
    // for varchar, `c1`(2) will take first two characters(bytes) as prefix index.
    // TODO: Note that TiDB only supports UTF-8, we need to check if prefix index behave differently
    // under other encoding methods
    int prefixLen = lengths.getOrDefault(columnRef, DataType.UNSPECIFIED_LEN);
    TypedKey literal = node.getTypedLiteral(prefixLen);
    RangeSet ranges = TreeRangeSet.create();

    switch (node.getRegType()) {
      case STARTS_WITH:
        ranges.add(Range.atLeast(literal).intersection(Range.lessThan(literal.next())));
        break;
      default:
        throwOnError(node);
    }
    return ranges;
  }
}