I have a partitioned table - with 201 partitions. I need to find latest partition in this table and use it to post process my data. The query to find list of all partitions is :
use db;
show partitions table_name;
I need a query to find the latest of these partitions. The partitions are in format
ingest_date=2016-03-09
I tried using max() which gave me a wrong result. I do not want to traverse through entire table by doing
select max(ingest_date) from db.table_name;
This would give me the expected output.. but kill the whole point of having partitions in the 1st place.
Is there a more efficient query to get the latest partition for HIve table ?
The only efficient way to list the partitions of a Hive table is to use the Metastore java API. Or to reverse-engineer the way partitions are organized in HDFS (quite straightforward actually) then list the directories, hoping HDFS and the Metastore are 100% in sync.
You can see Hive MetaStore tables,Partitions information in table of "PARTITIONS". You could use "TBLS" join "Partition" to query special table partitions.
You can run the HDFS list command to show all partition folders of a table from the Hive data warehouse location.
Use the MSCK REPAIR TABLE command to update the metadata in the catalog after you add Hive compatible partitions. The MSCK REPAIR TABLE command scans a file system such as Amazon S3 for Hive compatible partitions that were added to the file system after the table was created.
You can use "show partitions":
hive -e "set hive.cli.print.header=false;show partitions table_name;" | tail -1 | cut -d'=' -f2
This will give you "2016-03-09" as output.
If you want to avoid running the "show partitions" in hive shell as suggested above, you can apply a filter to your max() query. That will avoid doing a fulltable scan and results should be fairly quick!
select max(ingest_date) from db.table_name
where ingest_date>date_add(current_date,-3)
will only scan 2-3 partitions.
if you know your table location in hdfs. This is the most quick way without even opening the hive shell.
You can check you table location in hdfs using command;
show create table <table_name>
then
hdfs dfs -ls <table_path>| sort -k6,7 | tail -1
It will show latest partition location in hdfs
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