[HIVE-15995] Syncing metastore table with serde schema

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.2.1, 2.1.0, 3.0.0
• Fix Version/s: 3.0.0
• Component/s: Metastore
• Target Version/s: 3.0.0
• Assignee: Ádám Szita Assign to me
• Reporter: Michal Ferlinski
• Created: 21/Feb/17 11:58
• Updated: 23/May/18 00:00
• Resolved: 04/Apr/18 10:40

Description

Hive enables table schema evolution via properties. For avro e.g. we can alter the 'avro.schema.url' property to update table schema to the next version. Updating properties however doesn't affect column list stored in metastore DB so the table is not in the newest version when returned from metastore API. This is problem for tools working with metastore (e.g. Presto).

To solve this issue I suggest to introduce new DDL statement syncing metastore columns with those from serde:

ALTER TABLE user_test1 UPDATE COLUMNS

Note that this is format independent solution.

To reproduce, follow the instructions below:

• Create table based on avro schema version 1 (cxv1.avsc)

  CREATE EXTERNAL TABLE user_test1
    PARTITIONED BY (dt string)
    ROW FORMAT SERDE
    'org.apache.hadoop.hive.serde2.avro.AvroSerDe'
    STORED AS INPUTFORMAT
    'org.apache.hadoop.hive.ql.io.avro.AvroContainerInputFormat'
    OUTPUTFORMAT
    'org.apache.hadoop.hive.ql.io.avro.AvroContainerOutputFormat'
    LOCATION
    '/tmp/schema-evolution/user_test1'
    TBLPROPERTIES ('avro.schema.url'='/tmp/schema-evolution/cx1.avsc');
  

• Update schema to version 2 (cx2.avsc)

  ALTER TABLE user_test1 SET TBLPROPERTIES ('avro.schema.url' = '/tmp/schema-evolution/cx2.avsc');
  

• Print serde columns (top info) and metastore columns (Detailed Table Information):

  DESCRIBE EXTENDED user_test1