java - Hive, how do I retrieve all the database's tables columns

Question

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?

Answer 1

How can I access hive's metastore and retrieve all the columns of all the tables stored in a specific database?

This is one way to connect HiveMetaStoreClient and you can use method getTableColumnsInformation will get columns.

In this class along with columns all the other information like partitions can be extracted. pls see example client and sample methods.

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("
").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("");
                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("").join(partitionValues));
                sb.append("");
                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("
").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("");
                sb.append(cnt);
                sb.append("");
                cnt++;
                sb.append(fs.getName());
                sb.append("");
                sb.append(fs.getType());
                sb.append("");
                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;
        }
    }
}