Columnar_segments


#1

Any detail description about COLUMNAR_SEGMENTS table in information_schema. I know this is all about Columnstore table but i did not find detail of this table in online doc.


#2

Hello Jeetendra

Agree that we do not have detailed info about the table information_schema.columnar_segments but I think if you browse the contents of that table the column names and data will be self-explanatory.
If you create a columnstore table as follows: -
CREATE TABLE ram_colstore (
fld1 int(11) DEFAULT NULL,
fld2 char(15) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,
KEY fld2 (fld2) /*!90619 USING CLUSTERED COLUMNSTORE /,
/
!90618 SHARD / KEY fld1 (fld1)
) /
!90621 AUTOSTATS_ENABLED=TRUE */ |

then you would see entries like these in the columnar_segments table: -
memsql> select * from information_schema.columnar_segments where table_name = ‘ram_colstore’\G
*************************** 1. row ***************************
DATABASE_NAME: ramesh
TABLE_NAME: ram_colstore
COLUMN_NAME: fld1
SEGMENT_ID: 1
COLUMN_ID: 1
FILE: columns/ramesh_3/1/1/1
HOST: 127.0.0.1
PORT: 3307
NODE_ID: 2
PARTITION: 3
ROWS_COUNT: 2
DELETED_ROWS_COUNT: 0
ENCODING: Integer
MIN_VALUE: 2
MAX_VALUE: 4
SEGMENT_MIN_VALUE: black
SEGMENT_MAX_VALUE: white
UNCOMPRESSED_SIZE: 8
COMPRESSED_SIZE: 8
CREATION_TIME: 2019-05-08 18:31:17
LSN: 0
TERM: 0
CHECKSUM: 2634641714

If you have any specific question about a column, let us know and we can provide further information.

Thanks,
Ramesh Narayanan


#3

i want to know more about

SEGMENT_ID: 1
COLUMN_ID: 1
PARTITION: 3
MIN_VALUE: 2
MAX_VALUE: 4


#4

Jeetendra,

Here is the explanation.
SEGMENT_ID: 1 (assigned by MemSQL)
COLUMN_ID: 1 (First column)
PARTITION: 3 (assigned by MemSQL)
MIN_VALUE: 2 (minimum data value of the column)
MAX_VALUE: 4 (maximum data value of the column)

Ramesh