Hive优化器原理与源码解析系列--优化规则HiveReduceExpressionsWithStatsRule(二十三)

public boolean matches(RelOptRuleCall call)
{  
  return true;
}

public class RexShuttle
extends java.lang.Object
implements RexVisitor<RexNode>

@Override
public void onMatch(RelOptRuleCall call) {
  final Filter filter = call.rel(0);
  final RexBuilder rexBuilder = filter.getCluster().getRexBuilder();
  final RelMetadataQuery metadataProvider = RelMetadataQuery.instance();
  //1.可能通过从DNF表达式中提取公共元素来重新组合过滤器
  RexNode newFilterCondition = RexUtil.pullFactors(rexBuilder, filter.getCondition());
  //2.用统计信息，简化Filter过滤器
  RexReplacer replacer = new RexReplacer(filter, rexBuilder, metadataProvider);//遍历访问器
  newFilterCondition = replacer.apply(newFilterCondition);//遍历进行简化，生成简化后谓词表达式
  //3.如果创建了新的Filter过滤器则变换
  if (!filter.getCondition().toString().equals(newFilterCondition.toString())) {
    Filter newFilter = filter.copy(filter.getTraitSet(), filter.getInput(), newFilterCondition);
    call.transformTo(newFilter);//转换优化
  }
}

 private Pair<Number,Number> extractMaxMin(RexInputRef ref) {
      Number max = null;
      Number min = null;
      RelColumnOrigin columnOrigin = this.metadataProvider.getColumnOrigin(filterOp, ref.getIndex());
      if (columnOrigin != null) {
        RelOptHiveTable table = (RelOptHiveTable) columnOrigin.getOriginTable();//获取Hive table表对象
        if (table != null) {
          //ColStatistics对应的统计信息表字段信息
          ColStatistics colStats =
                 table.getColStat(Lists.newArrayList(columnOrigin.getOriginColumnOrdinal())).get(0);
          if (colStats != null && StatsSetupConst.areColumnStatsUptoDate(//判读该统计信息是否为最新
                  table.getHiveTableMD().getParameters(), colStats.getColumnName())) {
            Range range = colStats.getRange();//该列值范围
            if (range != null) {
              max = range.maxValue;//最大值
              min = range.minValue;//最小值
            }
          }
        }
      }
      return Pair.<Number,Number>of(max, min);
    }

private RexNode reduceCall(RexLiteral literal, SqlKind kind, Number max, Number min) {
{
  // Stats were available, try to reduce
  if (max != null && min != null) {
    BigDecimal maxVal = new BigDecimal(max.floatValue());
    BigDecimal minVal = new BigDecimal(min.floatValue());
    RexLiteral maxLiteral = rexBuilder.makeExactLiteral(maxVal, literal.getType());//转换为常量表达式
    RexLiteral minLiteral = rexBuilder.makeExactLiteral(minVal, literal.getType());
    //负整数、零或正整数，因为此对象小于、等于或大于指定对象。
    if (kind == SqlKind.EQUALS) {//1、谓词表达式的操作符号“=”
      if (minLiteral.getValue().compareTo(literal.getValue()) > 0 ||//小于最小值
              maxLiteral.getValue().compareTo(literal.getValue()) < 0) { //大于最大值
        return rexBuilder.makeLiteral(false);//返回False常量
      }
    }
    if (kind == SqlKind.GREATER_THAN) {//2、谓词表达式的操作符号“>”
      if (minLiteral.getValue().compareTo(literal.getValue()) > 0) {
        return rexBuilder.makeLiteral(true);
      } else if (maxLiteral.getValue().compareTo(literal.getValue()) <= 0) {
        return rexBuilder.makeLiteral(false);
      }
    } else if (kind == SqlKind.GREATER_THAN_OR_EQUAL) {//3、谓词表达式的操作符号“>=”
      if (minLiteral.getValue().compareTo(literal.getValue()) >= 0) {
        return rexBuilder.makeLiteral(true);
      } else if (maxLiteral.getValue().compareTo(literal.getValue()) < 0) {
        return rexBuilder.makeLiteral(false);
      }
    } else if (kind == SqlKind.LESS_THAN) {//4、谓词表达式的操作符号“<”
      if (minLiteral.getValue().compareTo(literal.getValue()) >= 0) {
        return rexBuilder.makeLiteral(false);
      } else if (maxLiteral.getValue().compareTo(literal.getValue()) < 0) {
        return rexBuilder.makeLiteral(true);
      }
    } else if (kind == SqlKind.LESS_THAN_OR_EQUAL) {//5、谓词表达式的操作符号“<=”
      if (minLiteral.getValue().compareTo(literal.getValue()) > 0) {
        return rexBuilder.makeLiteral(false);
      } else if (maxLiteral.getValue().compareTo(literal.getValue()) <= 0) {
        return rexBuilder.makeLiteral(true);
      }
    }
  }
  return null;
}