Alexander Behm created HIVE-15653:
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Summary: Some ALTER TABLE commands drop table stats
Key: HIVE-15653
URL: https://issues.apache.org/jira/browse/HIVE-15653
Project: Hive
Issue Type: Bug
Components: Metastore
Affects Versions: 1.1.0
Reporter: Alexander Behm
Priority: Critical
Some ALTER TABLE commands drop the table stats. That may make sense for some
ALTER TABLE operations, but certainly not for others. Personally, I I think
ALTER TABLE should only change what was requested by the user without any side
effects that may be unclear to users. In particular, collecting stats can be an
expensive operation so it's rather inconvenient for users if they get wiped
accidentally.
Repro:
{code}
create table t (i int);
insert into t values(1);
analyze table t compute statistics;
alter table t set tblproperties('test'='test');
hive> describe formatted t;
OK
# col_name data_type comment
i int
# Detailed Table Information
Database: default
Owner: abehm
CreateTime: Tue Jan 17 18:13:34 PST 2017
LastAccessTime: UNKNOWN
Protect Mode: None
Retention: 0
Location: hdfs://localhost:20500/test-warehouse/t
Table Type: MANAGED_TABLE
Table Parameters:
COLUMN_STATS_ACCURATE false
last_modified_by abehm
last_modified_time 1484705748
numFiles 1
numRows -1
rawDataSize -1
test test
totalSize 2
transient_lastDdlTime 1484705748
# Storage Information
SerDe Library: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe
InputFormat: org.apache.hadoop.mapred.TextInputFormat
OutputFormat:
org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat
Compressed: No
Num Buckets: -1
Bucket Columns: []
Sort Columns: []
Storage Desc Params:
serialization.format 1
Time taken: 0.169 seconds, Fetched: 34 row(s)
{code}
The same behavior can be observed with several other ALTER TABLE commands.
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