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What difference between columnar database (AWS Redshift, Azure Synapse, GCP Bigquery, Snowflake) and wide column database (AWS Keyspaces, Azure CosmosDB, GCP Bigtable, Hbase, Cassandra)?

What I understand so far:

  • Columnar databases are SQL (ACID transactions compliant)
  • And wide column databases are NoSQL (Scalability, etc)
  • Columnar databases (AWS Redshift, Azure Synapse, GCP Bigquery, Snowflake) are warehouses
  • And wide column databases (AWS Keyspaces, Azure CosmosDB, GCP Bigtable, Hbase, Cassandra) are just "pure" databases

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Wide column stores and column-oriented database systems store their data differently:

  • Column-oriented database systems store the data using a column-oriented data layout. Values for the same column are stored contiguously on disk.

  • Wide column stores group columns into column families (which usually have data of the same data type). According to Wikipedia:

Within a given column family, all data is stored in a row-by-row fashion, such that the columns for a given row are stored together, rather than each column being stored separately.

Data belonging to the same key is stored together. It uses multi-dimensional mapping to reference data by column, row and timestamp. (Timestamp, because new versions of the value in the cell/field are added rather than overwriting the previous value.)

Columnar databases (AWS Redshift, Azure Synapse, GCP Bigquery, Snowflake) are warehouses

Maybe it is more correct to say that columnar database systems are well suited for data warehouses.

ScyllaDB is another wide column store worth mentioning in addition to the ones you already listed.

See also:

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  • ScyllaDB is the same as Casandra since it's based on it... Commented Feb 1, 2023 at 20:49
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    @AlexisWilke I wouldn't say it's the same since it's completely rewritten in C++ while Cassandra is written in Java. That said, it is deliberately designed to be compatible with Cassandra by supporting CQL, Cassandra's query language, the same protocols and SSTable file format. But it also has other features not found in Cassandra. So I would consider ScyllaDB to be its own thing.
    – dbdemon
    Commented Feb 1, 2023 at 22:44

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