question Re: Failed with exception java.io.IOException:org.apache.hadoop.hive.ql.metadata.HiveException: java.lang.ClassCastException: org.apache.hadoop.hive.serde2.io.HiveDecimalWritable cannot be cast to org.apache.hadoop.io.LongWritable in Archives of Support Questions (Read Only)

Failed with exception java.io.IOException:org.apache.hadoop.hive.ql.metadata.HiveException: java.lang.ClassCastException: org.apache.hadoop.hive.serde2.io.HiveDecimalWritable cannot be cast to org.apache.hadoop.io.LongWritable

lsundar19 — Tue, 24 Jul 2018 20:14:23 GMT

Re: Failed with exception java.io.IOException:org.apache.hadoop.hive.ql.metadata.HiveException: java.lang.ClassCastException: org.apache.hadoop.hive.serde2.io.HiveDecimalWritable cannot be cast to org.apache.hadoop.io.LongWritable

lsundar19 — Tue, 24 Jul 2018 20:15:30 GMT

got the above error while select the records from hive table.

Re: Failed with exception java.io.IOException:org.apache.hadoop.hive.ql.metadata.HiveException: java.lang.ClassCastException: org.apache.hadoop.hive.serde2.io.HiveDecimalWritable cannot be cast to org.apache.hadoop.io.LongWritable

vmurakami — Sun, 29 Jul 2018 11:50:11 GMT

Hey @Sundar Lakshmanan!
Could you share with us the following output?

describe formatted <table_name>;

Usually, this happens to mismatched types or some data overflowing the datatype.
Are you able to do a simple query?

select * from <table_name> limit 10;

Hope this helps!

Re: Failed with exception java.io.IOException:org.apache.hadoop.hive.ql.metadata.HiveException: java.lang.ClassCastException: org.apache.hadoop.hive.serde2.io.HiveDecimalWritable cannot be cast to org.apache.hadoop.io.LongWritable

raja1010 — Sat, 14 Dec 2019 13:21:36 GMT

No i cant view the result of this simple query

Re: Failed with exception java.io.IOException:org.apache.hadoop.hive.ql.metadata.HiveException: java.lang.ClassCastException: org.apache.hadoop.hive.serde2.io.HiveDecimalWritable cannot be cast to org.apache.hadoop.io.LongWritable

alvarolucas — Fri, 30 May 2025 11:58:31 GMT

Instead of select *, you can use the column names you got from describe statement and identify the column with the issue (the type can be helpful there)

Re: Failed with exception java.io.IOException:org.apache.hadoop.hive.ql.metadata.HiveException: java.lang.ClassCastException: org.apache.hadoop.hive.serde2.io.HiveDecimalWritable cannot be cast to org.apache.hadoop.io.LongWritable

ggangadharan — Mon, 02 Jun 2025 13:55:49 GMT

It does looks like query failed with ClassCastException.

It indicates that ( org.apache.hadoop.hive.serde2.io.HiveDecimalWritable cannot be cast to org.apache.hadoop.io.LongWritable ) a mismatch between the data type Hive expects and the data type it's actually encountering while processing the query.

From the Error trace , Hive treats a value as a DECIMAL(HiveDecimalWritable) but the metadata seems to be Long(LongWritable).

One possible Reason might be Schema Mismatch:

Hive table schema defines a column but the underlying data file (e.g., Parquet, ORC, ...) for that column actually contains DECIMAL Values.

To validate ,

Run DESCRIBE FORMATTED <your_table_name>; for the table involved in the failing query.

Pay close attention to the data types of all columns, especially those that might be involved in the conversion.

Compare these Hive schema data types with the actual data types in your source data files. For example,

if you're using Parquet, use tools like parquet-tools to inspect the schema of Parquet files.

if you're using ORC , use hive --orcfiledump to inspect the schema of orc files.

Also make sure that Serde's pointing to valid underlying file formats.