In Hive, how do we search a table by name in all databases?
I am a Teradata user. Is there any counterpart of systems tables (present in Teradata) like dbc.tables, dbc.columns which are present in HIVE?
You can use SQL like to search a table.
Example:
I want to search a table with the name starting from "Benchmark" I don't know the rest of it.
Input in HIVE CLI:
show tables like 'ben*'
Output:
+-----------------------+--+
| tab_name |
+-----------------------+--+
| benchmark_core_month |
| benchmark_core_qtr |
| benchmark_core_year |
+-----------------------+--+
3 rows selected (0.224 seconds)
Or you can try below command if you are using Beeline
!tables
Note: It will work with Beeline only (JDBC client based)
More about beeline: http://blog.cloudera.com/blog/2014/02/migrating-from-hive-cli-to-beeline-a-primer/
you can also use hdfs to find a table in all databases:
the path of hive databases is:
/apps/hive/warehouse/
so, by using hdfs :
hdfs dfs -find /apps/hive/warehouse/ -name t*
You should query the metastore.
You can find the connection properties within hive-site.xml
bash
<$HIVE_HOME/conf/hive-site.xml grep -A1 jdo
<name>javax.jdo.option.ConnectionURL</name>
<value>jdbc:mysql://127.0.0.1/metastore?createDatabaseIfNotExist=true</value>
--
<name>javax.jdo.option.ConnectionDriverName</name>
<value>com.mysql.jdbc.Driver</value>
--
<name>javax.jdo.option.ConnectionUserName</name>
<value>hive</value>
--
<name>javax.jdo.option.ConnectionPassword</name>
<value>cloudera</value>
Within the metastore you can use a query similar to the following
mysql
select *
from metastore.DBS as d
join metastore.TBLS as t
on t.DB_ID =
d.DB_ID
where t.TBL_NAME like '% ... put somthing here ... %'
order by d.NAME
,t.TBL_NAME
;
Searching for tables with name containing infob across all Hive databases
for i in `hive -e "show schemas"`; do echo "Hive DB: $i"; hive -e "use $i; show tables"|grep "infob"; done
Hive stores all its metadata information in Metastore. Metastore schema can be found at: link: https://issues.apache.org/jira/secure/attachment/12471108/HiveMetaStore.pdf
It has tables like DBS for database, TBLS for tables and Columns. You may use appropriate join, to find out table name or column names.
#hisi's answer is elegant. However it induce an error with lacking memory for GC on our cluster. So, there is another less elegant approach that works for me.
Let foo is the table name to search. So
hadoop fs -ls -R -C /apps/hive/warehouse/ 2>/dev/null | grep '/apps/hive/warehouse/[^/]\{1,\}/foo$'
If one does not remember exact name of table but only substring bar in table name, then command is
hadoop fs -ls -R -C /apps/hive/warehouse/ 2>/dev/null | grep '/apps/hive/warehouse/[^/]\{1,\}/[^/]\{1,\}$' | grep bar
That's an extention of Mantej Singh's answer: you can use pyspark to find tables across all Hive databases (not just one):
from functools import reduce
from pyspark import SparkContext, HiveContext
from pyspark.sql import DataFrame
sc = SparkContext()
sqlContext = HiveContext(sc)
dbnames = [row.databaseName for row in sqlContext.sql('SHOW DATABASES').collect()]
tnames = []
for dbname in dbnames:
tnames.append(sqlContext.sql('SHOW TABLES IN {} LIKE "%your_pattern%"'.format(dbname)))
tables = reduce(DataFrame.union, tnames)
tables.show()
The way to do this is to iterate through the databases searching for table with a specified name.
Related
I am trying to create timestamp based partition in hive. But hive is creating data based partition. Below is my code. Could someone please help?
cat test1.sh
dat=`date +'%Y%m%d %H:%m:%S'`
hive -f load.hql -hiveconf file_load_timestamp=$dat;
cat load.hql
INSERT OVERWRITE table perm.test partition(file_load_timestamp='${hiveconf:dat}')
SELECT a,b FROM work.temp;
dt=20180102/ = HDFS path is getting created like this.
dt=20180102 103455/ = Expecting HDFS path to be created like this.
When I tried with %Y%m%d_%H:%m:%S' format its working as expected. But I need space between date and timestamp.
To create a folder name in HDFS with space in between, it is required to escape the space with \
hadoop fs -mkdir test\ 123
create a folder in hdfs with name test 123.
Similarly, hive maintains the partitions in folders created with the partition value. Thats why providing the date format %Y%m%d\ %H%m%S will help to create folder with spaces.
Below is tested and working:
INSERT OVERWRITE table person_details1 partition(datelocal='20180102\ 200128') select * from person_details;
datelocal is String
Edited:Executed the code, Below is working one:
hduser#Amit:~$ cat test1.sh
#!/bin/sh
dat=`date +'%Y%m%d\ %H%m%S'`
hive -f load.hql -hiveconf datelocal="$dat";
hduser#Amit:~$ cat load.hql
INSERT OVERWRITE table amit.person_details1 partition(datelocal='${hiveconf:datelocal}') select * from amit.person_details;
I have multiple Databases in Hive. A, B, C.
Database A has hive tables One, Two, Three. All three tables have different schemas.
How can I write a hive script to dump data of all three tables into a single csv file.
Try this.
#!/bin/bash
for db in A B C #List of databases
do
tbs=$(hive -S -e "use $db; show tables")
for tb in $tbs
do
hive -e "set hive.cli.print.header=true; use $db; SELECT * FROM $tb;" | sed 's/[\t]/,/g' >> sampleData.csv
done
done
I started an EC2 cluster on amazon to install cloudera...I got it installed and configured and loaded some of the Wiki Page Views public snapshot into HDFS. The structure of the files are as such:
projectcode, pagename, pageviews, bytes
the files are named as such:
pagecounts-20090430-230000.gz
date time
when loading the data from HDFS to Impala, I do it as such:
CREATE EXTERNAL TABLE wikiPgvws
(
project_code varchar(100),
page_name varchar(1000),
page_views int,
page_bytes int
)
ROW FORMAT DELIMITED FIELDS TERMINATED BY ' '
LOCATION '/user/hdfs';
one thing I missed is the date and time of each of the file. The dir:
/user/hdfs
contains multiple pagecount files associated with different dates and times. How can one pull that information and store it in a column when loading to impala?
I think the thing you are missing is the concept of partitions. If you define the table as partitioned, the data may be divided to different partitions based on the timestamp(in the name) of the file. I'm able to work around it in hive, I hope you to do the needful(if any) for impala as there query syntax is the same.
For me, this problem is not possible to solve only using hive. So I mixed up bash with hive scripting and it works fine for me. This is how I wrapped it up :
Create table wikiPgvws with partition
Create table wikiTmp with same fields as wikiPgvws except for partitions
For each file
i. Load data into wikiTmp
ii. grep timeStamp from fileName
iii. Use sed to replace placeholders in a predefined hql script file to load the data to the actual table. Then run it.
Drop table wikiTmp & remove tmp.hql
The script is as follows :
#!/bin/bash
hive -e "CREATE EXTERNAL TABLE wikiPgvws(
project_code varchar(100),
page_name varchar(1000),
page_views int,
page_bytes int
)
PARTITIONED BY(dts STRING)
ROW FORMAT DELIMITED FIELDS TERMINATED BY ' '
STORED AS TEXTFILE";
hive -e "CREATE TABLE wikiTmp(
project_code varchar(100),
page_name varchar(1000),
page_views int,
page_bytes int
)
ROW FORMAT DELIMITED FIELDS TERMINATED BY ' '
STORED AS TEXTFILE"
for fileName in $(hadoop fs -ls /user/hdfs/bounty/pagecounts-*.txt | grep -Po '(?<=\s)(/user.*$)')
do
echo "currentFile :$fileName"
dst=$(echo $filename | grep -oE '[0-9]{8}-[0-9]{6}')
echo "currentStamp $dst"
sed "s!sourceFile!'$fileName'!" t.hql > tmp.hql
sed -i "s!targetPartition!$dst!" tmp.hql
hive -f tmp.hql
done
hive -e "DROP TABLE wikiTmp"
rm -f tmp.hql
The hql script consists of just two lines :
LOAD DATA INPATH sourceFile OVERWRITE INTO TABLE wikiTmp;
INSERT OVERWRITE TABLE wikiPgvws PARTITION (dts = 'targetPartition') SELECT w.* FROM wikiTmp w;
Epilogue :
Check, whether options equivalent to hive -e & hive -f are available in impala. Without them, this script is of no use to you. Again the grep commands to fetch the fileName & timeStamp need to be modified according to your table location and stamp pattern. It's just one a way to show how the job can be done, but couldn't able to find another one.
Enhencement
If everything works well, consider merging the first two DDLs into another script to make it look cleaner. Although, I'm not sure that hql script arguments can be used to define partition values, still you can have a look to replace sed.
I have data in HDFS. And I wanted to load that data into hbase and hive table.
I have written a bash shell script in which I have written a pig script to load the data form HDFS to HBASE and also written hive script to load the data from HDFS to HIVE table which are working perfectly fine.Here my HDFS data files are with the same structure and I'm loading all the data files into single hbase and hive table.
Now my query is suppose if I receive some more data files in HDFS directory and if I run the shell script again it will create hbase and hive table again with the same name and tells table already exists. How can I write a hive and hbase query so that 1st it will check for the table existence, if table does not exists it create the table for the 1st time and load the data from HDFS to HBASE & Hive table. If the table is already exists then it will just insert the data into an existing hbase and hive table. It should not overwrite the data alreday exists in the tables.
How this can be done ?
Below is my script file: myScript.sh
echo "create 'goodtable','gt'" | hbase shell
pig -f a.pig -param input=/user/user/d/
hive -f h.hql
Where a.pig :
G = LOAD '$input' USING PigStorage(',') as (c1:chararray, c2:chararray,c3:chararray,c4:chararray,c5:chararray);
STORE G INTO 'hbase://goodtable' USING org.apache.pig.backend.hadoop.hbase.HBaseStorage('gt:name gt:state gt:phone_no gt:gender');
h.hql:
create external table hive_table(
id int,
name string,
state string,
phone_no int,
gender string) row format delimited fields terminated by ',' stored as textfile;
LOAD DATA INPATH '/user/user/d/' INTO TABLE hive_table;
I just wanted to add an example for HBase as Hive was already covered before:
if [[ $(echo "exists 'goodtable'" | hbase shell | grep 'not exist') ]];
then
echo "create 'goodtable','gt'" | hbase shell;
fi
For HIVE, you can add the command IF NOT EXISTS in the CREATE TABLE statement. See the documentation
I don't have much experience on Hbase, but I believe you can use EXISTS table_name command to check whether the table exists and then create the table is it doesn't exist. See here
#visakh is correct - you can see if table exists in HBase by entering the HBase shell, and typing : exists '<tablename>
In order to do this without entering the HBase shell interactively, you can create a simple ruby script such as the following:
exists 'mytable'
exit
Let's say you save this to a file called tabletest.rb. You can then execute this script by calling hbase shell tabletest.rb. This will create the following output, which you can then parse from your shell script:
Table tableisthere does exist
0 row(s) in 0.9830 seconds
OR
Table tableisNOTthere does not exist
0 row(s) in 0.9830 seconds
Adding more details for 'all in one' script:
Alternatively, you can create a more advanced script in ruby that checks for table existence and then will create it if needed - this is done calling the HBaseAdmin java api from within the ruby script.
conf = HBaseConfiguration.new
hbaseAdmin = HBaseAdmin.new(conf)
if !hbaseAdmin.tableExists('mytable')
hbaseAdmin.createTable('mytable',...)
end
select * from information_schema.columns;
In MySQL gives me the dbname, table name and column details of a MySQL db.
Can I get the same details in hive from any tables?
If you have configured your metastore in mysql .Then there are tables in the metastore database named DBS, COLUMNS_V2 which will have metadata of all hive DBs and tables .
Describe will meet your requirement.
hive -e "desc formatted tablename"
On above output you can use grep like below
hive -e "desc formatted tablename" |grep -i database
only column names can be get with below command.
hive -e "show columns from tablename"