Cao, Lionel created CARBONDATA-910:
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Summary: Implement Partition feature
Key: CARBONDATA-910
URL: https://issues.apache.org/jira/browse/CARBONDATA-910
Project: CarbonData
Issue Type: New Feature
Components: core, data-load, data-query
Reporter: Cao, Lionel
Assignee: Cao, Lionel
Why need partition table
Partition table provide an option to divide table into some smaller pieces.
With partition table:
1. Data could be better managed, organized and stored.
2. We can avoid full table scan in some scenario and improve query
performance. (partition column in filter,
multiple partition tables join in the same partition column etc.)
Partitioning design
Range Partitioning
range partitioning maps data to partitions according to the range of
partition column values, operator '<' defines non-inclusive upper bound of
current partition.
List Partitioning
list partitioning allows you map data to partitions with specific value
list
Hash Partitioning
hash partitioning maps data to partitions with hash algorithm and put
them to the given number of partitions
Composite Partitioning(2 levels at most for now)
Range-Range, Range-List, Range-Hash, List-Range, List-List, List-Hash,
Hash-Range, Hash-List, Hash-Hash
DDL-Create
Create table sales(
itemid long,
logdate datetime,
customerid int
...
...)
[partition by range logdate(...)]
[subpartition by list area(...)]
Stored By 'carbondata'
[tblproperties(...)];
range partition:
partition by range logdate(< '2016-01-01', < '2017-01-01', <
'2017-02-01', < '2017-03-01', < '2099-01-01')
list partition:
partition by list area('Asia', 'Europe', 'North America', 'Africa',
'Oceania')
hash partition:
partition by hash(itemid, 9)
composite partition:
partition by range logdate(< '2016- -01', < '2017-01-01', < '2017-02-01',
< '2017-03-01', < '2099-01-01')
subpartition by list area('Asia', 'Europe', 'North America', 'Africa',
'Oceania')
DDL-Rebuild, Add
Alter table sales rebuild partition by (range|list|hash)(...);
Alter table salse add partition (< '2018-01-01'); #only support range
partitioning, list partitioning
Alter table salse add partition ('South America');
#Note: No delete operation for partition, please use rebuild.
If need delete data, use delete statement, but the definition of partition will
not be deleted.
Partition Table Data Store
[Option One]
Use the current design, keep partition folder out of segments
Fact
|___Part0
| |___Segment_0
| |___ *******-[bucketId]-.carbondata
| |___ *******-[bucketId]-.carbondata
| |___Segment_1
| ...
|___Part1
| |___Segment_0
| |___Segment_1
|...
[Option Two]
remove partition folder, add partition id into file name and build btree in
driver side.
Fact
|___Segment_0
| |___ *******-[bucketId]-[partitionId].carbondata
| |___ *******-[bucketId]-[partitionId].carbondata
|___Segment_1
|___Segment_2
...
Pros & Cons:
Option one would be faster to locate target files
Option two need to store more metadata of folders
Partition Table MetaData Store
partitioni info should be stored in file footer/index file and load into memory
before user query.
Relationship with Bucket
Bucket should be lower level of partition.
Partition Table Query
Example:
Select * from sales
where logdate <= date '2016-12-01';
User should remember to add a partition filter when write SQL on a partition
table.
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