GBase 8s Data Compression Strategy Explained (Part 2)

This article (Chapter 2) provides a detailed overview of GBase 8s data compression features, including their purpose, methods, commands, and limitations. GBase 8s data compression is used when storage space is limited and you need to reduce data footprint and improve data processing efficiency. It is also recommended to compress inactive tables and fragments. It offers an effective solution for saving storage space and improving I/O efficiency.

04 Checking Data Compression Commands

1. onstat -g ppd: After performing data compression, you can view the data dictionary

Example: execute function task('table create_dictionary', ‘table', ‘db',‘gbasedbt');

onstat -g ppdpartnum ColOffset DbsNum CrTS CrLogID CrLogPos DrTS DrLogID DrLogPos0x1001d5 -1 1 1393371661 4 16339024 0 0 00x1001d5 4 1 1393371661 4 16355408 0 0 0

partnum: Partition number that the compression dictionary applies to

ColOffset: Byte offset of the BLOB column for a compressed partition; -1 indicates only rows are compressed

DbsNum: Number of dbspaces residing in the dictionary

CrTS: Timestamp when the data dictionary was created

CrLogID: Unique ID of the logical log generated when the data dictionary was created

CrLogPos: Position in the logical log when the data dictionary was created

DrTS: Timestamp when the data dictionary was cleared

DrLogID: Unique ID of the logical log generated when the data dictionary was cleared

DrLogPos: Position in the logical log when the data dictionary was cleared

2. Estimate Compression Ratio

execute function task("table estimate_compression", "tablename", "dbname", "owner_name"); est curr change partnum coloff table----- ----- ------ ------------- -----------------------------75.7% 75.3% +0.4 0x00200003 -1 insurance:bwilson.auto75.7% 0.0% +75.7 0x00300002 -1 insurance:pchang.home

est: Existing compression ratio

curr: Current compression ratio

change: Compression ratio change from existing to current

partnum: Fragment number

coloff: Evaluates whether the data in the dbspace is row data or BLOB data

table: Table name, database:owner.tablename

3. Print Currently Running Compression Operation Commands

onstat –g dsk Processed Remaining Duration Partnum OP Pass Rows Blobs Rows Time(s) Table Name400002 Repack 1 6325 1752 1497 00:00:00 db:sl:t1

partnum: Fragment number

OP: Compression operation, e.g., compress, repack, or shrink

Pass: For repack operations, 1 means row read pass, 2 means second pass

Processed Rows: Number of rows processed

Blobs: Number of BLOBs processed

Remaining Rows: Number of uncompressed rows

Duration Time(s): Duration of the operation in seconds

Table Name: Table name

05 Data Compression Limitations

The following cannot be compressed:

1. Data not stored by rows (BLOBs)

2. Indexes

3. Temporary tables

4. Catalog tables

5. Tables in system databases

GBase 8s data compression technology is an essential tool for DBAs and developers to optimize storage and improve performance. Through this detailed introduction, we hope to help you more effectively leverage GBase 8s compression features. Thank you for reading.