Data Format
Index Prefix Compression
Page Compression
WAL compression
Column Compression
Columnar Store
Misc approaches

Data Format

Efficient disk usage starts with proper data layout. Vendors strive to place data in pages in such a way that total overhead is kept as low as possible while still maintaining high read speed. Typically this is achieved as follows:

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Very slow lookups
Very slow updates

Examples:

Oracle Exadata Hybrid Columnar Compression - oragnize rows into groups, then transform them to columnar format and applies compression [1]
SQL Server Columnsotre Indexes - very similar to Oracle's idea [2] [3] [4]

[1] http://www.oracle.com/technetwork/database/features/availability/311358-132337.pdf
[2] https://msdn.microsoft.com/en-us/library/gg492088(v=sql.120).aspx
[3] https://docs.microsoft.com/en-us/sql/relational-databases/indexes/columnstore-indexes-overview?view=sql-server-2017
[4] https://docs.microsoft.com/en-us/sql/relational-databases/data-compression/data-compression?view=sql-server-2017#using-columnstore-and-columnstore-archive-compression

Draft materials

Compression options:

1) MISC

2) New algorithms (LSM, BWTree, ...)

https://www.percona.com/blog/2013/07/09/how-tokumx-gets-great-compression-for-mongodb/

https://github.com/facebook/mysql-5.6/wiki/MyRocks-advantages-over-InnoDB

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Postgres:

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Misc Approaches

Compressing large values

Large values, such as LOBs and long varchars, cannot be stored in original data block. Some vendors compress these values and then split into pieces.

Examples:

PostgreSQL TOAST [1]
Oracle Advanced LOB Compression [2] [3]

[1] https://wiki.postgresql.org/wiki/TOAST
[2] https://docs.oracle.com/database/121/ADLOB/adlob_smart.htm#ADLOB45944
[3] https://docs.microfocus.com/itom/Network_Automation:10.50/Administer/DB_Compression/ConfiguringLOB_Oracle

Compression during data load

Oracle attempts to compress values during data load (Direct Path, CTAS, INSERT ... APPEND) [1]. Compression is applied on per-block basis using dictionary approach. Oracle may decide to skip compression if there are no benefits. Alternatively, it may reorder attrbutes in rows to get longer common prefixes and improve compression ratio.

[1] https://www.

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