[hadoop] How to delete and update a record in Hive

I have installed Hadoop, Hive, Hive JDBC. which are running fine for me. But I still have a problem. How to delete or update a single record using Hive because delete or update command of MySQL is not working in Hive.

Thanks

hive> delete from student where id=1;
Usage: delete [FILE|JAR|ARCHIVE] <value> [<value>]*
Query returned non-zero code: 1, cause: null

If you want to delete all records then as a workaround load an empty file into table in OVERWRITE mode

hive> LOAD DATA LOCAL INPATH '/root/hadoop/textfiles/empty.txt' OVERWRITE INTO TABLE employee;
Loading data to table default.employee
Table default.employee stats: [numFiles=1, numRows=0, totalSize=0, rawDataSize=0]
OK
Time taken: 0.19 seconds

hive> SELECT * FROM employee;
OK
Time taken: 0.052 seconds

Configuration Values to Set for INSERT, UPDATE, DELETE In addition to the new parameters listed above, some existing parameters need to be set to support INSERT ... VALUES, UPDATE, and DELETE.

Configuration key Must be set to

hive.support.concurrency true (default is false) hive.enforce.bucketing true (default is false) (Not required as of Hive 2.0) hive.exec.dynamic.partition.mode nonstrict (default is strict)

Configuration Values to Set for Compaction

If the data in your system is not owned by the Hive user (i.e., the user that the Hive metastore runs as), then Hive will need permission to run as the user who owns the data in order to perform compactions. If you have already set up HiveServer2 to impersonate users, then the only additional work to do is assure that Hive has the right to impersonate users from the host running the Hive metastore. This is done by adding the hostname to hadoop.proxyuser.hive.hosts in Hadoop's core-site.xml file. If you have not already done this, then you will need to configure Hive to act as a proxy user. This requires you to set up keytabs for the user running the Hive metastore and add hadoop.proxyuser.hive.hosts and hadoop.proxyuser.hive.groups to Hadoop's core-site.xml file. See the Hadoop documentation on secure mode for your version of Hadoop (e.g., for Hadoop 2.5.1 it is at Hadoop in Secure Mode).

The UPDATE statement has the following limitations:

The expression in the WHERE clause must be an expression supported by a Hive SELECT clause.

Partition and bucket columns cannot be updated.

Query vectorization is automatically disabled for UPDATE statements. However, updated tables can still be queried using vectorization.

Subqueries are not allowed on the right side of the SET statement.

The following example demonstrates the correct usage of this statement:

UPDATE students SET name = null WHERE gpa <= 1.0;

DELETE Statement

Use the DELETE statement to delete data already written to Apache Hive.

DELETE FROM tablename [WHERE expression];

The DELETE statement has the following limitation: query vectorization is automatically disabled for the DELETE operation. However, tables with deleted data can still be queried using vectorization.

The following example demonstrates the correct usage of this statement:

DELETE FROM students WHERE gpa <= 1,0;

Yes, rightly said. Hive does not support UPDATE option. But the following alternative could be used to achieve the result:

Update records in a partitioned Hive table:

1. The main table is assumed to be partitioned by some key.
2. Load the incremental data (the data to be updated) to a staging table partitioned with the same keys as the main table.

3. Join the two tables (main & staging tables) using a LEFT OUTER JOIN operation as below:

   insert overwrite table main_table partition (c,d) select t2.a, t2.b, t2.c,t2.d from staging_table t2 left outer join main_table t1 on t1.a=t2.a;

In the above example, the main_table & the staging_table are partitioned using the (c,d) keys. The tables are joined via a LEFT OUTER JOIN and the result is used to OVERWRITE the partitions in the main_table.

A similar approach could be used in the case of un-partitioned Hive table UPDATE operations too.

Recently I was looking to resolve a similar issue, Apache Hive, Hadoop do not support Update/Delete operations. So ? So you have two ways:

1. Use a backup table: Save the whole table in a backup_table, then truncate your input table, then re-write only the data you are intrested to mantain.
2. Use Uber Hudi: It's a framework created by Uber to resolve the HDFS limitations including Deletion and Update. You can give a look in this link: https://eng.uber.com/hoodie/

an example for point 1:

Create table bck_table like input_table;
Insert overwrite table bck_table 
    select * from input_table;
Truncate table input_table;
Insert overwrite table input_table
    select * from bck_table where id <> 1;

NB: If the input_table is an external table you must follow the following link: How to truncate a partitioned external table in hive?

As of Hive version 0.14.0: INSERT...VALUES, UPDATE, and DELETE are now available with full ACID support.

INSERT ... VALUES Syntax:

INSERT INTO TABLE tablename [PARTITION (partcol1[=val1], partcol2[=val2] ...)] VALUES values_row [, values_row ...]

Where values_row is: ( value [, value ...] ) where a value is either null or any valid SQL literal

UPDATE Syntax:

UPDATE tablename SET column = value [, column = value ...] [WHERE expression]

DELETE Syntax:

DELETE FROM tablename [WHERE expression]

Additionally, from the Hive Transactions doc:

If a table is to be used in ACID writes (insert, update, delete) then the table property "transactional" must be set on that table, starting with Hive 0.14.0. Without this value, inserts will be done in the old style; updates and deletes will be prohibited.

Hive DML reference:
https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DML
Hive Transactions reference:
https://cwiki.apache.org/confluence/display/Hive/Hive+Transactions

Delete has been recently added in Hive version 0.14 Deletes can only be performed on tables that support ACID Below is the link from Apache .

https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DML#LanguageManualDML-Delete

Good news,Insert updates and deletes are now possible on Hive/Impala using Kudu.

You need to use IMPALA/kudu to maintain the tables and perform insert/update/delete records. Details with examples can be found here: insert-update-delete-on-hadoop

Please share the news if you are excited.

-MIK

The CLI told you where is your mistake : delete WHAT? from student ...

Delete : How to delete/truncate tables from Hadoop-Hive?

Update : Update , SET option in Hive

There are few properties to set to make a Hive table support ACID properties and to support UPDATE ,INSERT ,and DELETE as in SQL

Conditions to create a ACID table in Hive. 1. The table should be stored as ORC file .Only ORC format can support ACID prpoperties for now 2. The table must be bucketed

Properties to set to create ACID table:

set hive.support.concurrency =true;
set hive.enforce.bucketing =true;
set hive.exec.dynamic.partition.mode =nonstrict
set hive.compactor.initiator.on = true;
set hive.compactor.worker.threads= 1;
set hive.txn.manager = org.apache.hadoop.hive.ql.lockmgr.DbTxnManager;

set the property hive.in.test to true in hive.site.xml

After setting all these properties , the table should be created with tblproperty 'transactional' ='true'. The table should be bucketed and saved as orc

CREATE TABLE table_name (col1 int,col2 string, col3 int) CLUSTERED BY col1 INTO 4 
BUCKETS STORED AS orc tblproperties('transactional' ='true');

Now the Hive table can support UPDATE and DELETE queries

To achieve your current need, you need to fire below query

> insert overwrite table student 
> select *from student 
> where id <> 1;

This will delete current table and create new table with same name with all rows except the rows that you want to exclude/delete

I tried this on Hive 1.2.1

Upcoming version of Hive is going to allow SET based update/delete handling which is of utmost importance when trying to do CRUD operations on a 'bunch' of rows instead of taking one row at a time.

In the interim , I have tried a dynamic partition based approach documented here http://linkd.in/1Fq3wdb .

Please see if it suits your need.

You can delete rows from a table using a workaround, in which you overwrite the table by the dataset you want left into the table as a result of your operation.

insert overwrite table your_table 
    select * from your_table 
    where id <> 1
;

The workaround is useful mostly for bulk deletions of easily identifiable rows. Also, obviously doing this can muck up your data, so a backup of the table is adviced and care when planning the "deletion" rule also adviced.

Once you have installed and configured Hive , create simple table :

hive>create table testTable(id int,name string)row format delimited fields terminated by ',';

Then, try to insert few rowsin test table.

hive>insert into table testTable values (1,'row1'),(2,'row2');

Now try to delete records , you just inserted in table.

hive>delete from testTable where id = 1;

Error! FAILED: SemanticException [Error 10294]: Attempt to do update or delete using transaction manager that does not support these operations.

By default transactions are configured to be off. It is been said that update is not supported with the delete operation used in the conversion manager. To support update/delete , you must change following configuration.

cd  $HIVE_HOME
vi conf/hive-site.xml

Add below properties to file

<property>
  <name>hive.support.concurrency</name>
  <value>true</value>
 </property>
 <property>
  <name>hive.enforce.bucketing</name>
  <value>true</value>
 </property>
 <property>
  <name>hive.exec.dynamic.partition.mode</name>
  <value>nonstrict</value>
 </property>
 <property>
  <name>hive.txn.manager</name>
  <value>org.apache.hadoop.hive.ql.lockmgr.DbTxnManager</value>
 </property>
 <property>
  <name>hive.compactor.initiator.on</name>
  <value>true</value>
 </property>
 <property>
  <name>hive.compactor.worker.threads</name>
  <value>2</value>
 </property>

Restart the service and then try delete command again :

Error!

FAILED: LockException [Error 10280]: Error communicating with the metastore.

There is problem with metastore. In order to use insert/update/delete operation, You need to change following configuration in conf/hive-site.xml as feature is currently in development.

<property>
  <name>hive.in.test</name>
  <value>true</value>
 </property>

Restart the service and then delete command again :

hive>delete from testTable where id = 1;

Error!

FAILED: SemanticException [Error 10297]: Attempt to do update or delete on table default.testTable that does not use an AcidOutputFormat or is not bucketed.

Only ORC file format is supported in this first release. The feature has been built such that transactions can be used by any storage format that can determine how updates or deletes apply to base records (basically, that has an explicit or implicit row id), but so far the integration work has only been done for ORC.

Tables must be bucketed to make use of these features. Tables in the same system not using transactions and ACID do not need to be bucketed.

See below built table example with ORCFileformat, bucket enabled and ('transactional'='true').

hive>create table testTableNew(id int ,name string ) clustered by (id) into 2 buckets stored as orc TBLPROPERTIES('transactional'='true');

Insert :

hive>insert into table testTableNew values (1,'row1'),(2,'row2'),(3,'row3');

Update :

hive>update testTableNew set name = 'updateRow2' where id = 2;

Delete :

hive>delete from testTableNew where id = 1;

Test :

hive>select * from testTableNew ;

UPDATE or DELETE a record isn't allowed in Hive, but INSERT INTO is acceptable.
A snippet from Hadoop: The Definitive Guide(3rd edition):

Updates, transactions, and indexes are mainstays of traditional databases. Yet, until recently, these features have not been considered a part of Hive's feature set. This is because Hive was built to operate over HDFS data using MapReduce, where full-table scans are the norm and a table update is achieved by transforming the data into a new table. For a data warehousing application that runs over large portions of the dataset, this works well.

Hive doesn't support updates (or deletes), but it does support INSERT INTO, so it is possible to add new rows to an existing table.