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From Stefan Podkowinski <spo...@gmail.com>
Subject Re: How to use DBInputFormat?
Date Thu, 05 Feb 2009 10:37:17 GMT
The 0.19 DBInputFormat class implementation is IMHO only suitable for
very simple queries working on only few datasets. Thats due to the
fact that it tries to create splits from the query by
1) getting a count of all rows using the specified count query (huge
performance impact on large tables)
2) creating splits by issuing an individual query for each split with
a "limit" and "offset" parameter appended to the input sql query

Effectively your input query "select * from orders" would become
"select * from orders limit <splitlength> offset <splitstart>" and
executed until count has been reached. I guess this is not working sql
syntax for oracle.

Stefan


2009/2/4 Amandeep Khurana <amansk@gmail.com>:
> Adding a semicolon gives me the error "ORA-00911: Invalid character"
>
> Amandeep
>
>
> Amandeep Khurana
> Computer Science Graduate Student
> University of California, Santa Cruz
>
>
> On Wed, Feb 4, 2009 at 6:46 AM, Rasit OZDAS <rasitozdas@gmail.com> wrote:
>
>> Amandeep,
>> "SQL command not properly ended"
>> I get this error whenever I forget the semicolon at the end.
>> I know, it doesn't make sense, but I recommend giving it a try
>>
>> Rasit
>>
>> 2009/2/4 Amandeep Khurana <amansk@gmail.com>:
>> > The same query is working if I write a simple JDBC client and query the
>> > database. So, I'm probably doing something wrong in the connection
>> settings.
>> > But the error looks to be on the query side more than the connection
>> side.
>> >
>> > Amandeep
>> >
>> >
>> > Amandeep Khurana
>> > Computer Science Graduate Student
>> > University of California, Santa Cruz
>> >
>> >
>> > On Tue, Feb 3, 2009 at 7:25 PM, Amandeep Khurana <amansk@gmail.com>
>> wrote:
>> >
>> >> Thanks Kevin
>> >>
>> >> I couldnt get it work. Here's the error I get:
>> >>
>> >> bin/hadoop jar ~/dbload.jar LoadTable1
>> >> 09/02/03 19:21:17 INFO jvm.JvmMetrics: Initializing JVM Metrics with
>> >> processName=JobTracker, sessionId=
>> >> 09/02/03 19:21:20 INFO mapred.JobClient: Running job: job_local_0001
>> >> 09/02/03 19:21:21 INFO mapred.JobClient:  map 0% reduce 0%
>> >> 09/02/03 19:21:22 INFO mapred.MapTask: numReduceTasks: 0
>> >> 09/02/03 19:21:24 WARN mapred.LocalJobRunner: job_local_0001
>> >> java.io.IOException: ORA-00933: SQL command not properly ended
>> >>
>> >>         at
>> >>
>> org.apache.hadoop.mapred.lib.db.DBInputFormat.getRecordReader(DBInputFormat.java:289)
>> >>         at org.apache.hadoop.mapred.MapTask.run(MapTask.java:321)
>> >>         at
>> >> org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:138)
>> >> java.io.IOException: Job failed!
>> >>         at
>> org.apache.hadoop.mapred.JobClient.runJob(JobClient.java:1217)
>> >>         at LoadTable1.run(LoadTable1.java:130)
>> >>         at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:65)
>> >>         at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:79)
>> >>         at LoadTable1.main(LoadTable1.java:107)
>> >>         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>> >>         at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
>> >>         at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown
>> Source)
>> >>         at java.lang.reflect.Method.invoke(Unknown Source)
>> >>         at org.apache.hadoop.util.RunJar.main(RunJar.java:165)
>> >>         at org.apache.hadoop.mapred.JobShell.run(JobShell.java:54)
>> >>         at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:65)
>> >>         at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:79)
>> >>         at org.apache.hadoop.mapred.JobShell.main(JobShell.java:68)
>> >>
>> >> Exception closing file
>> >>
>> /user/amkhuran/contract_table/_temporary/_attempt_local_0001_m_000000_0/part-00000
>> >> java.io.IOException: Filesystem closed
>> >>         at
>> org.apache.hadoop.hdfs.DFSClient.checkOpen(DFSClient.java:198)
>> >>         at
>> org.apache.hadoop.hdfs.DFSClient.access$600(DFSClient.java:65)
>> >>         at
>> >>
>> org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.closeInternal(DFSClient.java:3084)
>> >>         at
>> >>
>> org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.close(DFSClient.java:3053)
>> >>         at
>> >> org.apache.hadoop.hdfs.DFSClient$LeaseChecker.close(DFSClient.java:942)
>> >>         at org.apache.hadoop.hdfs.DFSClient.close(DFSClient.java:210)
>> >>         at
>> >>
>> org.apache.hadoop.hdfs.DistributedFileSystem.close(DistributedFileSystem.java:243)
>> >>         at
>> >> org.apache.hadoop.fs.FileSystem$Cache.closeAll(FileSystem.java:1413)
>> >>         at org.apache.hadoop.fs.FileSystem.closeAll(FileSystem.java:236)
>> >>         at
>> >> org.apache.hadoop.fs.FileSystem$ClientFinalizer.run(FileSystem.java:221)
>> >>
>> >>
>> >> Here's my code:
>> >>
>> >> public class LoadTable1 extends Configured implements Tool  {
>> >>
>> >>       // data destination on hdfs
>> >>       private static final String CONTRACT_OUTPUT_PATH =
>> "contract_table";
>> >>
>> >>       // The JDBC connection URL and driver implementation class
>> >>
>> >> private static final String CONNECT_URL = "jdbc:oracle:thin:@dbhost
>> >> :1521:PSEDEV";
>> >>       private static final String DB_USER = "user";
>> >>       private static final String DB_PWD = "pass";
>> >>       private static final String DATABASE_DRIVER_CLASS =
>> >> "oracle.jdbc.driver.OracleDriver";
>> >>
>> >>       private static final String CONTRACT_INPUT_TABLE =
>> >> "OSE_EPR_CONTRACT";
>> >>
>> >>       private static final String [] CONTRACT_INPUT_TABLE_FIELDS = {
>> >>         "PORTFOLIO_NUMBER", "CONTRACT_NUMBER"};
>> >>
>> >>       private static final String ORDER_CONTRACT_BY_COL =
>> >> "CONTRACT_NUMBER";
>> >>
>> >>
>> >>     static class ose_epr_contract implements Writable, DBWritable {
>> >>
>> >>
>> >>         String CONTRACT_NUMBER;
>> >>
>> >>
>> >>         public void readFields(DataInput in) throws IOException {
>> >>
>> >>             this.CONTRACT_NUMBER = Text.readString(in);
>> >>
>> >>         }
>> >>
>> >>         public void write(DataOutput out) throws IOException {
>> >>
>> >>             Text.writeString(out, this.CONTRACT_NUMBER);
>> >>
>> >>
>> >>         }
>> >>
>> >>         public void readFields(ResultSet in_set) throws SQLException {
>> >>
>> >>             this.CONTRACT_NUMBER = in_set.getString(1);
>> >>
>> >>         }
>> >>
>> >>         @Override
>> >>         public void write(PreparedStatement prep_st) throws SQLException
>> {
>> >>             // TODO Auto-generated method stub
>> >>
>> >>         }
>> >>
>> >>     }
>> >>
>> >>     public static class LoadMapper extends MapReduceBase
>> >>                                 implements Mapper<LongWritable,
>> >> ose_epr_contract, Text, NullWritable> {
>> >>         private static final char FIELD_SEPARATOR = 1;
>> >>
>> >>         public void map(LongWritable arg0, ose_epr_contract arg1,
>> >>                 OutputCollector<Text, NullWritable> arg2, Reporter
arg3)
>> >>                 throws IOException {
>> >>
>> >>             StringBuilder sb = new StringBuilder();
>> >> ;
>> >>             sb.append(arg1.CONTRACT_NUMBER);
>> >>
>> >>
>> >>             arg2.collect(new Text (sb.toString()), NullWritable.get());
>> >>
>> >>         }
>> >>
>> >>     }
>> >>
>> >>
>> >>     public static void main(String[] args) throws Exception {
>> >>         Class.forName("oracle.jdbc.driver.OracleDriver");
>> >>         int exit = ToolRunner.run(new LoadTable1(), args);
>> >>
>> >>     }
>> >>
>> >>     public int run(String[] arg0) throws Exception {
>> >>         JobConf conf = new JobConf(getConf(), LoadTable1.class);
>> >>
>> >>         conf.setInputFormat(DBInputFormat.class);
>> >>         DBConfiguration.configureDB(conf, DATABASE_DRIVER_CLASS,
>> >> CONNECT_URL, DB_USER, DB_PWD);
>> >>
>> >>         DBInputFormat.setInput(conf, ose_epr_contract.class,
>> >>                 "select CONTRACT_NUMBER from OSE_EPR_CONTRACT",
>> >>                 "select COUNT(CONTRACT_NUMBER) from OSE_EPR_CONTRACT");
>> >>         FileOutputFormat.setOutputPath(conf, new
>> >> Path(CONTRACT_OUTPUT_PATH));
>> >>
>> >>         conf.setMapperClass(LoadMapper.class);
>> >>         conf.setNumReduceTasks(0);
>> >>
>> >>         conf.setOutputKeyClass(Text.class);
>> >>         conf.setOutputValueClass(NullWritable.class);
>> >>
>> >>         JobClient.runJob(conf);
>> >>
>> >>         return 0;
>> >>     }
>> >> }
>> >>
>> >> -Amandeep
>> >>
>> >> Amandeep Khurana
>> >> Computer Science Graduate Student
>> >> University of California, Santa Cruz
>> >>
>> >>
>> >> On Tue, Feb 3, 2009 at 6:51 PM, Kevin Peterson <kpeterson@biz360.com
>> >wrote:
>> >>
>> >>> On Tue, Feb 3, 2009 at 5:49 PM, Amandeep Khurana <amansk@gmail.com>
>> >>> wrote:
>> >>>
>> >>> > In the setInput(...) function in DBInputFormat, there are two sets
of
>> >>> > arguments that one can use.
>> >>> >
>> >>> > 1. public static void *setInput*(JobConf
>> >>> >
>> >>> > a) In this, do we necessarily have to give all the fieldNames (which
>> are
>> >>> > the
>> >>> > column names right?) that the table has, or do we need to specify
>> only
>> >>> the
>> >>> > ones that we want to extract?
>> >>>
>> >>>
>> >>> You may specify only those columns that you are interested in.
>> >>>
>> >>> b) Do we have to have a orderBy or not necessarily? Does this relate
to
>> >>> the
>> >>> > primary key in the table in any ways?
>> >>>
>> >>>
>> >>> Conditions and order by are not necessary.
>> >>>
>> >>> a) Is there any restriction on the kind of queries that this function
>> >>> > can take in the inputQuery string?
>> >>>
>> >>>
>> >>> I don't think so, but I don't use this method -- I just use the
>> fieldNames
>> >>> and tableName method.
>> >>>
>> >>>
>> >>> > I am facing issues in getting this to work with an Oracle database
>> and
>> >>> > have no idea of how to debug it (an email sent earlier).
>> >>> > Can anyone give me some inputs on this please?
>> >>>
>> >>>
>> >>> Create a new table that has one column, put about five entries into
>> that
>> >>> table, then try to get a map job working that outputs the values to
a
>> text
>> >>> file. If that doesn't work, post your code and errors.
>> >>>
>> >>
>> >>
>> >
>>
>>
>>
>> --
>> M. Raşit ÖZDAŞ
>>
>

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