Compression

Dictionary Encoding

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

Multi-version Concurrency Control (MVCC)

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

Relational

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

Indexes

Block Range Index (BRIN)

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

Read Committed

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

Joins

Hash Join

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

SQL