Size of tables in PostgreSQL vs Apache Cassandra…

PostgreSQL table with ts+key as primary key:  ~43GB

PostgreSQL wide column table with ts as primary key : 247GB
Cassandra wide column table with ts as primary  key: 4.5GB

Strange that in PostgreSQL a table with much less rows (but much more columns) needs a lot of more space (both tables store the same amount of data). )

It seems that the Apache Cassandra Column Store can compress the columns pretty good – factor 10 less disk space!

The source table in PostgreSQL (TimescaleDB) with a timestamp and a key column and 8 data columns had about 170 Mio rows.

    instrument character varying(10) NOT NULL,
    ts timestamp(3) without time zone NOT NULL,
    o numeric,
    h numeric,
    l numeric,
    c numeric,
    primary key (instrument, ts)

I needed to flatten the table so that i have just the timestamp as primary key and many columns and each column is of a type. It ends up in a table with about 1.6 Mio rows and many columns.

    o       float,
    c       float,
    h       float,
    l       float,
    volume  float

CREATE TABLE candles_wide
   ts timestamp(3) without time zone NOT NULL,
   AU200_AUD price,
   AUD_CAD price,
   AUD_CHF price,
   AUD_HKD price,
   AUD_JPY price,
   AUD_NZD price,
   ... 124 columns

Apache Cassandra wide column store table with ts as primary key and many columns.

CREATE TABLE candles (ts timestamp,
   AU200_AUD tuple<float,float,float,float,float>,    
   AUD_CAD tuple<float,float,float,float,float>,  
   AUD_CHF tuple<float,float,float,float,float>,  
   ... 124 tuples