[jira] [Created] (IMPALA-6864) COMPUTE STATS overwrites table schema in Hive Metastore

["Clemens Valiente (JIRA)" <ji...@apache.org>]

Clemens Valiente created IMPALA-6864:
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             Summary: COMPUTE STATS overwrites table schema in Hive Metastore
                 Key: IMPALA-6864
                 URL: https://issues.apache.org/jira/browse/IMPALA-6864
             Project: IMPALA
          Issue Type: Bug
          Components: Catalog
    Affects Versions: Impala 2.9.0
            Reporter: Clemens Valiente


If Impala does not have the latest schema information from Hive, a COMPUTE STATS overwrites the table definition stored in Hive Metastore.

short example:

{code:sql}
# Hive
create table cvaliente.testschema (id int);
{code}
{code:sql}
# Impala
INVALIDATE METADATA cvaliente.testschema;
{code}
{code:sql}
# Hive
drop table cvaliente.testschema;
create table cvaliente.testschema (id int, value string);
{code}
{code:sql}
# Impala
COMPUTE STATS cvaliente.testschema;
{code}
{code:sql}
# Hive
show columns from cvaliente.testschema
{code}

In our case, due to the size and scope of our table we did {{REFRESH TABLE dbname.tblname PARTITION (partkey = partvalue)}} in impala 
followed by {{COMPUTE INCREMENTAL STATS dbname.tblname PARTITION (partkey = partvalue)}}
REFRESH TABLE ... PARTITION does not update the table schema unlike a simple REFRESH PARTITION so it kept the old schema and the COMPUTE INCREMENTAL STATS... PARTITION then updated the full table back with the old schema in Hive metastore.

- a REFRESH TABLE ... PARTITION should still update the table metadata from hive metastore
- a COMPUTE STATS should only write column statistics back to the metastore and NOT update the table schema.



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