利用SemanticAnalyzerHook来过滤不加分区条件的Hive查询

    我们Hadoop集群中将近百分之80的作业是通过Hive来提交的，由于Hive写起来简单便捷，而且我们又提供了Hive Web Client，所以使用范围很广，包括ba，pm，po，sales都在使用hive进行ad-hoc查询，但是hive在降低用户使用门槛的同时，也使得用户经常写不合理开销很大的语句，生成了很多的mapreduce job，占用了大量slot数，其中最典型的例子就是分区表查询，不指定分区条件，导致hive没有做partition pruner优化，进而读入了所有的表数据，占用大量IO和计算资源。

        

    为了尽可能规避这种情况，我们可以利用了hive的hook机制，在hook中实现一些方法来对语句做预判，第一期先不会直接block住语句，而是记录有问题的语句来公告警示.

        

    具体做法是实现HiveSemanticAnalyzerHook接口，preAnalyze方法和postAnalyze方法会分别在compile函数之前和之后执行，我们只要实现preAnalyze方法，遍历传进来的ASTNode抽象语法树，获取左子树的From表名和右子树的where判断条件key值，如果该From表是分区表的话，会通过metastore client获取它的所有分区key名字，用户指定的where条件中只要出现任何一个分区key，则此语句通过检测，否则会在标准错误中输出一条warning，并且在后台log中记录用户名和执行语句，每隔一段时间会将这些bad case在hive-user组邮箱进行公示，希望能通过这种方式来起到相互警示和学习的效果.

compile函数中根据hiveconf中指定的hive.semantic.analyzer.hook来反射实例化hook类，此处为实现AbstractSemanticAnalyzerHook的DPSemanticAnalyzerHook

package org.apache.hadoop.hive.ql.parse;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import org.apache.commons.lang.StringUtils;
import org.apache.hadoop.hive.metastore.api.FieldSchema;
import org.apache.hadoop.hive.ql.exec.Task;
import org.apache.hadoop.hive.ql.metadata.Hive;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.metadata.Table;
import org.apache.hadoop.hive.ql.session.SessionState;
import org.apache.hadoop.hive.ql.session.SessionState.LogHelper;
import org.apache.hadoop.hive.shims.ShimLoader;

public class DPSemanticAnalyzerHook extends AbstractSemanticAnalyzerHook {
  private final static String NO_PARTITION_WARNING = "WARNING: HQL is not efficient, Please specify partition condition! HQL:%s ;USERNAME:%s";

  private final SessionState ss = SessionState.get();
  private final LogHelper console = SessionState.getConsole();
  private Hive hive = null;
  private String username;
  private String currentDatabase = "default";
  private String hql;
  private String whereHql;
  private String tableAlias;
  private String tableName;
  private String tableDatabaseName;
  private Boolean needCheckPartition = false;

  @Override
  public ASTNode preAnalyze(HiveSemanticAnalyzerHookContext context, ASTNode ast)
      throws SemanticException {
    try {
      hql = ss.getCmd().toLowerCase();
      hql = StringUtils.replaceChars(hql, '\n', ' ');
      if (hql.contains("where")) {
        whereHql = hql.substring(hql.indexOf("where"));
      }
      username = ShimLoader.getHadoopShims().getUserName(context.getConf());

      if (ast.getToken().getType() == HiveParser.TOK_QUERY) {
        try {
          hive = context.getHive();
          currentDatabase = hive.getCurrentDatabase();
        } catch (HiveException e) {
          throw new SemanticException(e);
        }

        extractFromClause((ASTNode) ast.getChild(0));

        if (needCheckPartition && !StringUtils.isBlank(tableName)) {
          String dbname = StringUtils.isEmpty(tableDatabaseName) ? currentDatabase
              : tableDatabaseName;
          String tbname = tableName;
          String[] parts = tableName.split(".");
          if (parts.length == 2) {
            dbname = parts[0];
            tbname = parts[1];
          }
          Table t = hive.getTable(dbname, tbname);
          if (t.isPartitioned()) {
            if (StringUtils.isBlank(whereHql)) {
              console.printError(String.format(NO_PARTITION_WARNING, hql, username));
            } else {
              List<FieldSchema> partitionKeys = t.getPartitionKeys();
              List<String> partitionNames = new ArrayList<String>();
              for (int i = 0; i < partitionKeys.size(); i++) {
                partitionNames.add(partitionKeys.get(i).getName().toLowerCase());
              }

              if (!containsPartCond(partitionNames, whereHql, tableAlias)) {
                console.printError(String.format(NO_PARTITION_WARNING, hql, username));
              }
            }
          }
        }

      }
    } catch (Exception ex) {
      ex.printStackTrace();
    }
    return ast;
  }

  private boolean containsPartCond(List<String> partitionKeys, String sql, String alias) {
    for (String pk : partitionKeys) {
      if (sql.contains(pk)) {
        return true;
      }
      if (!StringUtils.isEmpty(alias) && sql.contains(alias + "." + pk)) {
        return true;
      }
    }
    return false;
  }

  private void extractFromClause(ASTNode ast) {
    if (HiveParser.TOK_FROM == ast.getToken().getType()) {
      ASTNode refNode = (ASTNode) ast.getChild(0);
      if (refNode.getToken().getType() == HiveParser.TOK_TABREF && ast.getChildCount() == 1) {
        ASTNode tabNameNode = (ASTNode) (refNode.getChild(0));
        int refNodeChildCount = refNode.getChildCount();
        if (tabNameNode.getToken().getType() == HiveParser.TOK_TABNAME) {
          if (tabNameNode.getChildCount() == 2) {
            tableDatabaseName = tabNameNode.getChild(0).getText().toLowerCase();
            tableName = BaseSemanticAnalyzer.getUnescapedName((ASTNode) tabNameNode.getChild(1))
                .toLowerCase();
          } else if (tabNameNode.getChildCount() == 1) {
            tableName = BaseSemanticAnalyzer.getUnescapedName((ASTNode) tabNameNode.getChild(0))
                .toLowerCase();
          } else {
            return;
          }

          if (refNodeChildCount == 2) {
            tableAlias = BaseSemanticAnalyzer.unescapeIdentifier(refNode.getChild(1).getText())
                .toLowerCase();
          }
          needCheckPartition = true;
        }
      }
    }
  }

  @Override
  public void postAnalyze(HiveSemanticAnalyzerHookContext context,
      List<Task<? extends Serializable>> rootTasks) throws SemanticException {
    // LogHelper console = SessionState.getConsole();
    // Set<ReadEntity> readEntitys = context.getInputs();
    // console.printInfo("Total Read Entity Size:" + readEntitys.size());
    // for (ReadEntity readEntity : readEntitys) {
    // Partition p = readEntity.getPartition();
    // Table t = readEntity.getTable();
    // }
  }
}

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