7

I want to write the equivalent of this sql request in Hive : 

select * from information_schema.columns where table_schema='database_name'

How can I access hive's metastore and retrieve all the columns of all the tables stored in a specific database? I know that we can do it by table via describe [table_name] but is there anyway to have all the columns for all the tables in a database in the same request?

4

2 回答 2

7

如何访问 hive 的元存储并检索存储在特定数据库中的所有表的所有列？

这是一种连接方式HiveMetaStoreClient，您可以使用 getTableColumnsInformation 方法获取列。

在这个类和列中，可以提取所有其他信息，如分区。请参阅示例客户端和示例方法。

import org.apache.hadoop.hive.conf.HiveConf;

// test program
public class Test {
    public static void main(String[] args){

        HiveConf hiveConf = new HiveConf();
        hiveConf.setIntVar(HiveConf.ConfVars.METASTORETHRIFTCONNECTIONRETRIES, 3);
        hiveConf.setVar(HiveConf.ConfVars.METASTOREURIS, "thrift://host:port");

        HiveMetaStoreConnector hiveMetaStoreConnector = new HiveMetaStoreConnector(hiveConf);
        if(hiveMetaStoreConnector != null){
            System.out.print(hiveMetaStoreConnector.getAllPartitionInfo("tablename"));
        }
    }
}


// define a class like this

import com.google.common.base.Joiner;
import com.google.common.collect.Lists;
import org.apache.hadoop.hive.conf.HiveConf;
import org.apache.hadoop.hive.metastore.HiveMetaStoreClient;
import org.apache.hadoop.hive.metastore.api.FieldSchema;
import org.apache.hadoop.hive.metastore.api.MetaException;
import org.apache.hadoop.hive.metastore.api.Partition;
import org.apache.hadoop.hive.metastore.api.hive_metastoreConstants;
import org.apache.hadoop.hive.ql.metadata.Hive;
import org.apache.thrift.TException;
import org.joda.time.DateTime;
import org.joda.time.format.DateTimeFormatter;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class HiveMetaStoreConnector {
    private HiveConf hiveConf;
    HiveMetaStoreClient hiveMetaStoreClient;

    public HiveMetaStoreConnector(String msAddr, String msPort){
        try {
            hiveConf = new HiveConf();
            hiveConf.setVar(HiveConf.ConfVars.METASTOREURIS, msAddr+":"+ msPort);
            hiveMetaStoreClient = new HiveMetaStoreClient(hiveConf);
        } catch (MetaException e) {
            e.printStackTrace();
            System.err.println("Constructor error");
            System.err.println(e.toString());
            System.exit(-100);
        }
    }

    public HiveMetaStoreConnector(HiveConf hiveConf){
        try {
            this.hiveConf = hiveConf;
            hiveMetaStoreClient = new HiveMetaStoreClient(hiveConf);
        } catch (MetaException e) {
            e.printStackTrace();
            System.err.println("Constructor error");
            System.err.println(e.toString());
            System.exit(-100);
        }
    }

    public String getAllPartitionInfo(String dbName){
        List<String> res = Lists.newArrayList();
        try {
            List<String> tableList = hiveMetaStoreClient.getAllTables(dbName);
            for(String tableName:tableList){
                res.addAll(getTablePartitionInformation(dbName,tableName));
            }
        } catch (MetaException e) {
            e.printStackTrace();
            System.out.println("getAllTableStatistic error");
            System.out.println(e.toString());
            System.exit(-100);
        }

        return Joiner.on("\n").join(res);
    }

    public List<String> getTablePartitionInformation(String dbName, String tableName){
        List<String> partitionsInfo = Lists.newArrayList();
        try {
            List<String> partitionNames = hiveMetaStoreClient.listPartitionNames(dbName,tableName, (short) 10000);
            List<Partition> partitions = hiveMetaStoreClient.listPartitions(dbName,tableName, (short) 10000);
            for(Partition partition:partitions){
                StringBuffer sb = new StringBuffer();
                sb.append(tableName);
                sb.append("\t");
                List<String> partitionValues = partition.getValues();
                if(partitionValues.size()<4){
                    int size = partitionValues.size();
                    for(int j=0; j<4-size;j++){
                        partitionValues.add("null");
                    }
                }
                sb.append(Joiner.on("\t").join(partitionValues));
                sb.append("\t");
                DateTime createDate = new DateTime((long)partition.getCreateTime()*1000);
                sb.append(createDate.toString("yyyy-MM-dd HH:mm:ss"));
                partitionsInfo.add(sb.toString());
            }

        } catch (TException e) {
            e.printStackTrace();
            return Arrays.asList(new String[]{"error for request on" + tableName});
        }

        return partitionsInfo;
    }

    public String getAllTableStatistic(String dbName){
        List<String> res = Lists.newArrayList();
        try {
            List<String> tableList = hiveMetaStoreClient.getAllTables(dbName);
            for(String tableName:tableList){
                res.addAll(getTableColumnsInformation(dbName,tableName));
            }
        } catch (MetaException e) {
            e.printStackTrace();
            System.out.println("getAllTableStatistic error");
            System.out.println(e.toString());
            System.exit(-100);
        }

        return Joiner.on("\n").join(res);
    }

    public List<String> getTableColumnsInformation(String dbName, String tableName){
        try {
            List<FieldSchema> fields = hiveMetaStoreClient.getFields(dbName, tableName);
            List<String> infs = Lists.newArrayList();
            int cnt = 0;
            for(FieldSchema fs : fields){
                StringBuffer sb = new StringBuffer();
                sb.append(tableName);
                sb.append("\t");
                sb.append(cnt);
                sb.append("\t");
                cnt++;
                sb.append(fs.getName());
                sb.append("\t");
                sb.append(fs.getType());
                sb.append("\t");
                sb.append(fs.getComment());
                infs.add(sb.toString());
            }

            return infs;

        } catch (TException e) {
            e.printStackTrace();
            System.out.println("getTableColumnsInformation error");
            System.out.println(e.toString());
            System.exit(-100);
            return null;
        }
    }
}
于 2016-10-17T09:02:55.283 回答
5

如果您希望能够运行返回 hive 元数据的此类查询，您可以使用 MySQL 设置 Hive Metastore，Hive 中使用的元数据存储在 MySQL 的特定帐户中。

您必须通过执行为 hive 创建 MySQL 用户CREATE USER 'hive'@'metastorehost' IDENTIFIED BY 'mypassword'。

COLUMNS_VS然后你会找到与你正在寻找的信息类似的表格。

检索所有表中所有列的示例查询可能是：SELECT COLUMN_NAME, TBL_NAME FROM COLUMNS_V2 c JOIN TBLS a ON c.CD_ID=a.TBL_ID

或者，您可以通过对WebHCat的REST 调用访问此信息，请参阅wiki了解更多信息。

于 2015-10-15T16:53:46.243 回答