Compression

PieCloudDB utilizes a hybrid row-column storage approach, where data of the same type is clustered together. This provides excellent compression rates for dictionary-based compression algorithms.

Concurrency Control

In PieCloudDB, the concurrency control scheme used by each coordinator instance is Multi-Version Concurrency Control (MVCC). This approach ensures that each transaction reads from a consistent snapshot of the database that remains unaltered by concurrent transactions. MVCC offers several advantages over lock-based concurrency control in PieCloudDB, particularly in terms of performance.

Data Model

PieCloudDB is a rational database, compatible with the complete SQL standard.

Indexes

PieCloudDB does not support normal index because dense index is extremely expensive for OLAP scenario. However, PieCloudDB uses min-max based pruning, and other techniques to accelerate data access.

Isolation Levels

PieCloudDB support two isolation levels: Read Committed and Repeatable Read.

Joins

PieCloudDB support multiple joins, including Hash Join, Merge Join and Nested Loop Join. And PieCloudDB also support two logical joins: Semi Join and Anti Join, which are used to support sub-link pull up.

Query Interface