Elliot West created HIVE-11092:
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Summary: First delta of an ORC ACID table contains incorrect schema
Key: HIVE-11092
URL: https://issues.apache.org/jira/browse/HIVE-11092
Project: Hive
Issue Type: Bug
Components: Hive
Reporter: Elliot West
Assignee: Elliot West
Priority: Minor
I've been reading ORC ACID data that backs transactional tables from a process
external to Hive. Initially I tried to use 'schema on read' but found some
inconsistencies in the schema returned from the initial delta file and
subsequent delta and base files. To reproduce the issue by example:
{code}
CREATE TABLE base_table ( id int, message string )
PARTITIONED BY ( continent string, country string )
CLUSTERED BY (id) INTO 1 BUCKETS
STORED AS ORC
TBLPROPERTIES ('transactional' = 'true');
INSERT INTO TABLE base_table PARTITION (continent = 'Asia', country = 'India')
VALUES (1, 'x'), (2, 'y'), (3, 'z');
UPDATE base_table SET message = 'updated' WHERE id = 1;
{code}
Now examining the raw data with the {{orcfiledump}} utility (edited for
brevity):
{code}
cd hive/warehouse/base_table/continent=Asia/country=India/
hive --orcfiledump delta_0000001_0000001/bucket_00000
Type:
struct<operation:int,originalTransaction:bigint,bucket:int,rowId:bigint,currentTransaction:bigint,row:struct<_col0:int,_col1:string>>
hive --orcfiledump delta_0000002_0000002/bucket_00000
Type:
struct<operation:int,originalTransaction:bigint,bucket:int,rowId:bigint,currentTransaction:bigint,row:struct<id:int,message:string>>
{code}
The row schema for the first delta that resulted from the inserts has its field
names erased: {{row:struct<_col0:int,_col1:string>}}, whereas the delta for the
update reports the correct schema: {{row:struct<id:int,message:string>}}. I
have also checked this with my own reader code so am confident that
{{FileDump}} is not at fault.
I believe that the row field names, and hence schema, should be consistent
across all ORC files in the ACID data set. This will enable schema on read with
field access by name (not index), which is currently not possible. Therefore
I'd like to get this issue resolved.
I'm happy to work on this, however after working through {{OrcRecordUpdater}}
and {{FileSinkOperator}} and related tests I've failed to reproduce or isolate
the issue at a smaller scale. I'd be grateful for some suggestions on where to
look next.
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