How do we get the 1000 tables description using hive? - hadoop

Question

I have 1000 tables, need to check the describe <table name>; for one by one. Instead of running one by one, can you please give me one command to fetch "N" number of tables in a single shot.

Answer 1

You can make a shell script and call it with a parameter. For example following script receives schema, prepares list of tables in the schema, calls DESCRIBE EXTENDED command, extracts location, prints table location for first 1000 tables in the schema ordered by name. You can modify and use it as a single command:
#!/bin/bash
#Create table list for a schema (script parameter)
HIVE_SCHEMA=$1
echo Processing Hive schema $HIVE_SCHEMA...
tablelist=tables_$HIVE_SCHEMA
hive -e " set hive.cli.print.header=false; use $HIVE_SCHEMA; show tables;" 1> $tablelist
#number of tables
tableNum_limit=1000
#For each table do:
for table in $(cat $tablelist|sort|head -n "$tableNum_limit") #add proper sorting
do
echo Processing table $table ...
#Call DESCRIBE
out=$(hive client -S -e "use $HIVE_SCHEMA; DESCRIBE EXTENDED $table")
#Get location for example
table_location=$(echo "${out}" | egrep -o 'location:[^,]+' | sed 's/location://')
echo Table location: $table_location
#Do something else here
done

Answer 2

Query the metastore
Demo
Hive
create database my_db_1;
create database my_db_2;
create database my_db_3;
create table my_db_1.my_tbl_1 (i int);
create table my_db_2.my_tbl_2 (c1 string,c2 date,c3 decimal(12,2));
create table my_db_3.my_tbl_3 (x array<int>,y struct<i:int,j:int,k:int>);
MySQL (Metastore)
use metastore
;
select d.name as db_name
,t.tbl_name
,c.integer_idx + 1 as col_position
,c.column_name
,c.type_name
from DBS as d
join TBLS as t
on t.db_id =
d.db_id
join SDS as s
on s.sd_id =
t.sd_id
join COLUMNS_V2 as c
on c.cd_id =
s.cd_id
where d.name like 'my\_db\_%'
order by d.name
,t.tbl_name
,c.integer_idx
;
+---------+----------+--------------+-------------+---------------------------+
| db_name | tbl_name | col_position | column_name | type_name |
+---------+----------+--------------+-------------+---------------------------+
| my_db_1 | my_tbl_1 | 1 | i | int |
| my_db_2 | my_tbl_2 | 1 | c1 | string |
| my_db_2 | my_tbl_2 | 2 | c2 | date |
| my_db_2 | my_tbl_2 | 3 | c3 | decimal(12,2) |
| my_db_3 | my_tbl_3 | 1 | x | array<int> |
| my_db_3 | my_tbl_3 | 2 | y | struct<i:int,j:int,k:int> |
+---------+----------+--------------+-------------+---------------------------+