Data Organization Google Professional Data Engineer GCP

• Every row in Bigtable is indexed by a single row key.
• Row keys are byte strings that may be up to 64 KB
• Row keys enables to retrieve several related rows quickly as a single, contiguous scan over the row key.
• Each row may contain thousands of columns
• Bigtable only scans the row key when performing lookups.
• Reads and writes are performed at the row level.
• Data is stored in scalable tables, each of which is a sorted key/value map.
• Each row describes a single entity,
• Columns contain individual values for each row.
• Each row is indexed by a single row key
• Columns if related are grouped into a column family.
• Column is identified by column family and a column qualifier.
• Each row/column intersection can contain multiple cells, or versions, at different timestamps
• Tables are sparse; if a cell does not contain any data, it does not take up any space.

For example, suppose you’re building a social network for United States presidents—let’s call it Prezzy. Each president can follow posts from other presidents. The following illustration shows a Cloud Bigtable table that tracks who each president is following on Prezzy:

In above figure,

• The table has single column family – “follows” having many column qualifiers.
• Above, uses column qualifiers as data as Bigtable handles sparseness and will be able to add new ones quickly.
• Row key is username and assuming they are evenly spread, it gives quick access and update