I have a Hive table SMART_STG.CALL_RECORDS which is external non-partitioned text file table. I need to copy the data into a new target table. The requirements for the target table is:
Should have same structure as source table - SMART_STG.CALL_RECORDS
Should have partitioning on new column 'ingest_datetime'
This new table should get created automatically
I know I can create the partitioned table manually by using describe option and adding the partitioned BY(ingest_datetime string) but how do I build this table dynamically so that my code works on any table?
Sample structure of my source table.
create table SMART_STG.CALL_RECORDS
(
Call_Number String,
Dollar_Amt Decimal(3,2),
Call_Value Decimal(3,2),
Date_Month INT,
Date_year INT
)
STORED AS TEXTFILE
LOCATION '/smart_stg/CallRecords'
Related
Suppose I have internal orc non partitioned table in Hive:
CREATE TABLE IF NOT EXISTS non_partitioned_table(
id STRING,
company STRING,
city STRING,
country STRING,
)
STORED AS ORC;
Is it possible somehow create parquet partitioned table this way via cte like statement?
create partitioned_table PARTITION ON (date STRING) like non_partitioned_table;
alter table partitioned_table SET FILEFORMAT PARQUET;
This create statement doesn't work.
So basically I need to add column and make table partitioned by this column. I know that I can create table through the simple create table statement, but I need to do it within CREATE TABLE LIKE and the altered somehow
Your table doesn't have a date column to begin with, so you're going to have to make a new one.
You might be able to ALTER TABLE non_partitioned_table ADD PARTITION, but haven't tried that myself. If you want to try it, I would suggest the partition location be outside of the existing HDFS directory.
Anyways, the CREATE-TABLE-LIKE DDL does not support PARTITIONED BY
CREATE [TEMPORARY] [EXTERNAL] TABLE [IF NOT EXISTS] [db_name.]table_name
LIKE existing_table_or_view_name
[LOCATION hdfs_path];
You need to copy the DESCRIBE TABLE schema from the first, then alter it and add the PARTITIONED BY, and optionally specify STORED AS. (SET FILEFORMAT PARQUET doesn't change the data type in-place).
Then, if you want the data in the new table, you need to INSERT OVERWRITE TABLE
On using PARTITIONED BY or CLUSTERED BY keywords while creating Hive tables,
hive would create separate files corresponding to each partition or bucket. But for external tables is this still valid. As my understanding is data files corresponding to external files are not managed by hive. So does hive create additional files corresponding to each partition or bucket and move corresponding data in to these files.
Edit - Adding details.
Few extracts from "Hadoop: Definitive Guide" - "Chapter 17: Hive"
CREATE TABLE logs (ts BIGINT, line STRING) PARTITIONED BY (dt STRING, country STRING);
When we load data into a partitioned table, the partition values are specified explicitly:
LOAD DATA LOCAL INPATH 'input/hive/partitions/file1' INTO TABLE logs PARTITION (dt='2001-01-01', country='GB');
At the filesystem level, partitions are simply nested sub directories of the table directory.
After loading a few more files into the logs table, the directory structure might look like this:
The above table was obviously a managed table, so hive had the ownership of data and created a directory structure for each partition as in the above tree structure.
In case of external table
CREATE EXTERNAL TABLE logs (ts BIGINT, line STRING) PARTITIONED BY (dt STRING, country STRING);
Followed by same set of load operations -
LOAD DATA LOCAL INPATH 'input/hive/partitions/file1' INTO TABLE logs PARTITION (dt='2001-01-01', country='GB');
How will hive handle these partitions. As for external tables with out partition, hive will simply point to the data file and fetch any query result by parsing the data file. But in case of loading data in to a partitioned external table, where are the partitions created.
Hope fully in hive warehouse? Can someone support or clarify this?
Suppose partitioning on date as this is a common thing to do.
CREATE EXTERNAL TABLE mydatabase.mytable (
var1 double
, var2 INT
, date String
)
PARTITIONED BY (date String)
LOCATION '/user/location/wanted/';
Then add all your partitions;
ALTER TABLE mytable ADD PARTITION( date = '2017-07-27' );
ALTER TABLE mytable ADD PARTITION( date = '2017-07-28' );
So on and so forth.
Finally you can add your data in the proper location. You will have an external partitioned file.
There is an easy way to do this.
Create your External Hive table first.
CREATE EXTERNAL TABLE database.table (
id integer,
name string
)
PARTITIONED BY (country String)
LOCATION 'xxxx';
Next you have to run a MSCK command (metastore consistency check)
msck repair table database.table
This command will recover all partitions that are available in your path and update the metastore. Now, if you run your query against your table, data from all partitions will be retrieved.
Creating partition table in hive, does it mandatory to choose always the last column for partition column.
If I choose 1st column as partition, I cant do filter data, is there any way to choose first column for partition?
In hive, if you want to partition a table, you have to define partition column first during table creation time. & while populating the data into table you need to specify as follow:
"INSERT INTO partitioned_table PARTITION(status) SELECT id , name, status from temp_tbl "
in this way using you can partition based on last column only. if you want to partition on the basis of first column. you have to write a Mapreduce job for that . that is the only option available.
I guess the problem you are facing is that you already have table "source" in your local system or hdfs and you want to upload it to partitioned table. And you want the first column in the source table to be partitioned in hive. As the source table does not have headers i guess we can not do anything here if we try to directly upload the file in the hive destination folder. The only alternate way i know is that create a non partitioned table in hive whose structure is exactly the same as the source file. then upload the source data to non partitioned table first, then copy the data from non partitioned table to partitioned table.
Suppose the source file is like this
create table source(eid int, ename int, esal int) partitioned by (dept string)
your non partioned table where you upload the data is like thiscreate table nopart(dept string, esal int,ename string, eid int)
then you use the dynamic partition by command insert overwrite table source partition(dept) select eid,ename,esal,dept from nopart;
the order of the parameters is the only point here.
I have successfully created and added Dynamic partitions in an Internal table in hive. i.e. by using following steps:
1-created a source table
2-loaded data from local into source table
3- created another table with partitions - partition_table
4- inserted the data to this table from source table resulting in creation of all the partitions dynamically
My question is, how to perform this in external table? I read so many articles on this, but i am confused , that do I have to specify path to the already existing partitions for creating partitions for external table??
example:
Step 1:
create external table1 ( name string, age int, height int)
location 'path/to/dataFile/in/HDFS';
Step 2:
alter table table1 add partition(age)
location 'path/to/already/existing/partition'
I am not sure how to proceed with partitioning in external tables. Can somebody please help by giving step by step description of the same?.
Thanks in advance!
Yes, you have to tell Hive explicitly what is your partition field.
Consider you have a following HDFS directory on which you want to create a external table.
/path/to/dataFile/
Let's say this directory already have data stored(partitioned) department wise as follows:
/path/to/dataFile/dept1
/path/to/dataFile/dept2
/path/to/dataFile/dept3
Each of these directories have bunch of files where each file
contains actual comma separated data for fields say name,age,height.
e.g.
/path/to/dataFile/dept1/file1.txt
/path/to/dataFile/dept1/file2.txt
Now let's create external table on this:
Step 1. Create external table:
CREATE EXTERNAL TABLE testdb.table1(name string, age int, height int)
PARTITIONED BY (dept string)
ROW FORMAT DELIMITED
STORED AS TEXTFILE
LOCATION '/path/to/dataFile/';
Step 2. Add partitions:
ALTER TABLE testdb.table1 ADD PARTITION (dept='dept1') LOCATION '/path/to/dataFile/dept1';
ALTER TABLE testdb.table1 ADD PARTITION (dept='dept2') LOCATION '/path/to/dataFile/dept2';
ALTER TABLE testdb.table1 ADD PARTITION (dept='dept3') LOCATION '/path/to/dataFile/dept3';
Done, run select query once to verify if data loaded successfully.
1. Set below property
set hive.exec.dynamic.partition=true
set hive.exec.dynamic.partition.mode=nonstrict
2. Create External partitioned table
create external table1 ( name string, age int, height int)
location 'path/to/dataFile/in/HDFS';
3. Insert data to partitioned table from source table.
Basically , the process is same. its just that you create external partitioned table and provide HDFS path to table under which it will create and store partition.
Hope this helps.
The proper way to do it.
Create the table and mention it is partitioned.
create external table1 ( name string, age int, height int)
partitioned by (age int)
stored as ****(your format)
location 'path/to/dataFile/in/HDFS';
Now you have to refresh the partitions in the hive metastore.
msck repair table table1
This will take care of loading all your partitions into the hive metastore.
You can use msck repair table at any point during your process to have the metastore updated.
Follow the below steps:
Create a temporary table/Source table
create table source_table(name string,age int,height int) row format delimited by ',';
Use your delimiter as in the file instead of ',';
Load data into the source table
load data local inpath 'path/to/dataFile/in/HDFS';
Create external table with partition
create external table external_dynamic_partitions(name string,height int)
partitioned by (age int)
location 'path/to/dataFile/in/HDFS';
Enable dynamic partition mode to nonstrict
set hive.exec.dynamic.partition.mode=nonstrict
Load data to external table with partitions from source file
insert into table external_dynamic partition(age)
select * from source_table;
That's it.
You can check the partitions information using
show partitions external_dynamic;
You can even check if it is an external table or not using
describe formatted external_dynamic;
External table is a type of table in Hive where the data is not moved to the hive warehouse. That means even if U delete the table, the data still persists and you will always get the latest data, which is not the case with Managed table.
I have a Hive table TEST with this configuration:
create external table if not exists TEST (
ID bigint,
ACTIVITY_ID string,
BATCH_NBR
)
PARTITIONED BY (year INT, month INT, day INT)
CLUSTERED BY (BATCH_NBR) into 20 buckets
ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t'
LOCATION '/user/lake/hive/test';
And I have Hive files in this location which I can easily load into Hive table and it works.
/user/lake/hive/test/2013/01/01/part-r-00001
Now if I create another table STORE and insert some data from this TEST table, folder structures are getting changes for the Test table. I was expecting after loading the same data, location for the STORE table will have something like this:
/user/core/store/2014/07/03/batch123231.1313
But the above location changed to this:
/user/core/store/year=2013/month=01/day=01/
I'm using insert overwrite table STORE select * from TEST; query for loading STORE table from TEST.
How can I load that table and preserve the same folder structure in destination?
Internal table in Hive will follow their own/default folder structure in /apps/hive/warehouse folder and will not preserve folder structure if the data is loaded from an external Hive table. I was using internal table for "Store", so it was not working as expected.