We are using netezza direct to import data from Netezza to Hadoop as part of POC.
Have couple of questions on Netezza specific and Netezza Sqoop Integration.
Q1. Does Sqoop direct mode always require CREATE EXTERNAL TABLE and DROP privilege to perform direct transfer?
Q2. Does external table get created in Netezza ? If yes, which database ? I see Sqoop using below query :
CREATE EXTERNAL TABLE '/yarn/local/usercache/someuser/appcache/application_1483624176418_42787/work/task_1483624176418_42787_m_000000/nzexttable-0.txt'
USING (REMOTESOURCE 'JDBC'
BOOLSTYLE 'T_F'
CRINSTRING FALSE DELIMITER 44 ENCODING
'internal' FORMAT 'Text' INCLUDEZEROSECONDS TRUE
NULLVALUE 'null' MAXERRORS 1)
AS SELECT * FROM SOME_TBL WHERE (DATASLICEID % 3)
Does it create in Database selected in db URL ? jdbc:netezza://somehostname:5480/SOME_DB_1
Q3. If Netezza needs to create External tables, can it create the external table in different database than the one which the actual table with data that needs to be pulled into Hadoop. What is the config change that needs to be done ?
Q4. Does Sqoop run DROP table on external table which was created by individual mappers ?
Sqoop command Used :
export HADOOP_CLASSPATH=/opt/nz/lib/nzjdbc3.jar
sqoop import -D mapreduce.job.queuename=some_queue
-D yarn.nodemanager.local-dirs=/tmp -D mapreduce.map.log.level=DEBUG
--direct --connect jdbc:netezza://somehost:5480/SOME_DB --table SOME_TBL_1
--username SOMEUSER --password xxxxxxx --target-dir /tmp/netezza/some_tbl_file
--num-mappers 2 --verbose
This is what I got as reply in Sqoop User community (Thanks Szabolcs Vasas).
In case of Netezza direct imports Sqoop executes a CREATE EXTERNAL TABLE command (so you will need CREATE EXTERNAL TABLE privilege) to create a backup of the content of the table to a temporary file and it copies the content of this file to the final output on HDFS.
The SQL command you pasted in your email is indeed the one which is executed by Sqoop but as far as I understand from the Netezza documentation (http://www.ibm.com/support/knowledgecenter/SSULQD_7.2.1/com.ibm.nz.load.doc/c_load_create_external_tbl_expls.html, 6th example) this does not really create a new external table in any schema it just backs up the content of the table and because of that no DROP TABLE statement is executed.
Q1. Yes, Sqoop need CREATE EXTERNAL TABLE but not DROP privilege.
Q2. Sqoop does not really create a new external table in any schema it just backs up the content of the table (http://www.ibm.com/support/knowledgecenter/SSULQD_7.2.1/com.ibm.nz.load.doc/c_load_create_external_tbl_expls.html, 6th example).
Q3. Not possible to create an EXTERNAL table in a specific schema.
Q4. No, Sqoop does not run DROP command.
Moreover, the table created by sqoop direct process is Netezza TET - Transient external tables. Thus, the external remotesource JDBC table is dropped once the mapper receives the data as NamedFifo. Thus tables are not stored in Netezza after the transfer.
Related
There are more than 300 tables in my hive environment.
I want to export all the tables from Hive to Oracle/MySql including metadata.
My Oracle database doesn't have any tables corresponding to these Hive tables.
Sqoop import from Oracle to Hive creates tables in Hive if the table doesn't exists.But Sqoop export from Hive to Oracle doesn't create table if not exists and fails with an exception.
Is there any option in Sqoop to export metadata also? or
Is there any other Hadoop tool through which I can achieve this?
Thanks in advance
The feature you're asking for isn't in Spark. I don't know of a current hadoop tool which can do what you're asking either unfortunately. A potential workaround is using the "show create table mytable" statement in Hive. It will return the create table statements. You can parse this manually or pragmatically via awk and get the create tables in a file, then run this file against your oracle db. From there, you can use sqoop to populate the tables.
It won't be fun.
Sqoop can't copy metadata or create table in RDBMS on the basis of Hive table.
Table must be there in RDBMS to perform sqoop export.
Why is it so?
Mapping from RDBMS to Hive is easy because hive have only few datatypes(10-15). Mapping from multiple RDBMS datatypes to Hive datatype is easily achievable. But vice versa is not that easy. Typical RDBMS has 100s of datatypes (that too different in different RDBMS).
Also sqoop export is newly added feature. This feature may come in future.
Using sqoop I can create managed table but not the externale table.
Please let me know what are the best practices to unload data from data warehouse and load them in Hive external table.
1.The tables in warehouse are partitioned. Some are date wise partitioned some are state wise partitioned.
Please put your thoughts or practices used in production environment.
Sqoop does not support creating Hive external tables. Instead you might:
Use the Sqoop codegen command to generate the SQL for creating the Hive internal table that matches your remote RDBMS table (see http://sqoop.apache.org/docs/1.4.2/SqoopUserGuide.html#_literal_sqoop_codegen_literal)
Modify the generated SQL to create a Hive external table
Execute the modified SQL in Hive
Run your Sqoop import command, loading into the pre-created Hive external table
Step 1: import data from mysql to hive table.
sqoop import
--connect jdbc:mysql://localhost/
--username training --password training
--table --hive-import --hive-table -m 1
--fields-terminated-by ','
Step 2: In hive change the table type from Managed to External.
Alter table <Table-name> SET TBLPROPERTIES('EXTERNAL'='TRUE')
Note:you can import directly into hive table or else to back end of hive.
My best suggestion is to SQOOP your data to HDFS and create EXTERNAL for Raw operations and Transformations.
Finally mashed up data to the internal table. I believe this is one of the best practices to get things done in a proper way.
Hope this helps!!!
Refer to these links:
https://mapr.com/blog/what-kind-hive-table-best-your-data/
In the above if you want to skip directly to the point -->2.2.1 External or Internal
https://hadoopsters.net/2016/07/15/hive-tables-internal-and-external-explained/
After referring to the 1st link then second will clarify most of your questions.
Cheers!!
What is the difference between Apache Sqoop and Hive? I know that sqoop is used to import/export data from RDBMS to HDFS and Hive is a SQL layer abstraction on top of Hadoop. Can I can use Sqoop for importing data into HDFS and then use Hive for querying?
Yes, you can. In fact many people use sqoop and hive for exactly what you have told.
In my project what I had to do was to load the historical data from my RDBMS which was oracle, move it to HDFS. I had hive external tables defined for this path. This allowed me to run hive queries to do transformations. Also, we used to write mapreduce programs on top of these data to come up with various analysis.
Sqoop transfers data between HDFS and relational databases. You can use Sqoop to transfer data from a relational database management system (RDBMS) such as MySQL or Oracle into HDFS and use MapReduce on the transferred data. Sqoop can export this transformed data back into an RDBMS as well. More info http://sqoop.apache.org/docs/1.4.3/index.html
Hive is a data warehouse software that facilitates querying and managing large datasets residing in HDFS. Hive provides schema on read (as opposed to schema on write for RDBMS) onto the data and the ability to query the data using a SQL-like language called HiveQL. More info https://hive.apache.org/
Yes you can. As a matter of fact, that's exactly how it is meant to be used.
Sqoop :
We can integrate with any external data sources with HDFS i.e Sql , NoSql and Data warehouses as well using this tool at the same time we export it as well since this can be used as bi-directional ways.
sqoop to move data from a relational database into Hbase.
Hive: 1.As per my understanding we can import the data from Sql databases into hive rather than NoSql Databases.
We can't export the data from HDFS into Sql Databases.
We can use both together using the below two options
sqoop create-hive-table --connect jdbc:mysql://<hostname>/<dbname> --table <table name> --fields-terminated-by ','
The above command will generate the hive table and this table name will be same name in the external table and also the schema
Load the data
hive> LOAD DATA INPATH <filename> INTO TABLE <filename>
Hive can be shortened to one step if you know that you want to import stright from a database directly into hive
sqoop import --connect jdbc:mysql://<hostname>/<dbname> --table <table name> -m 1 --hive-import
I have an oracle table which has 80 columns and id partitioned on state column. My requirement is to create a hive table with similar schema of oracle table and partitioned on state.
I tried using sqoop -create-hive-table option. But keep getting an error
ERROR sqoop.Sqoop: Got exception running Sqoop: java.lang.IllegalArgumentException: Partition key state cannot be a column to import.
I understand that in Hive the partitioned column should not be in table definition, but then how do I get around the issue?
I do not want to manually write create table command, as I have 50 such tables to import and would like to use sqoop.
Any suggestion or ideas?
Thanks
There is a turn around for this.
Below is the procedure i fallow :
On Oracle run query to get the schema for a table and store it to a file.
Move that file to Hadoop
On Hadoop create a shell script which constructs a HQL file.
That hql file contains "Hive create table statement along with columns". For this we can use the above file(Oracle schema file copied to hadoop).
For this script to run u need to just pass Hive database name,table name, partition column name,path, etc.. depending on u r customization level.At the end of this shell script add "hive -f HQL filename".
If everything is ready it just takes couple of mins for each table creation.
We are having different data base schemas in Oracle. We are planning to sqoop some of the tables from oracle to Hive ware house. But If we put sqooping of tables of an oltp is sequential it is working. But to have a better usage we are planning to sqoop different oltps tables parallay, but it is faling to sqoop same table parallay.
It seems while sqooping a Table, one temporary table will be created in hdfs by sqoop and from there it will move the data to hive table, because of that reason we are not able to sqoop parallay.
Is there any way that we sqoop same tables parallay.
You can use parameter --target-dir to specify arbitrary temporary directory on HDFS where Sqoop will import data first. This parameter should be working in conjunction with --hive-import.