Joins

Hash Join Sort-Merge Join

Isolation Levels

Snapshot Isolation

Storage Model

Hybrid

Vector uses an adaptive storage model based on PAX partitions. By default, Vector stores tables in columnar model. Nullable attribute has a boolean type column which is stored together with the attribute column. However, if there exists an index where the key spans multiple attributes, these columns are grouped together and stored in the same block. For small tables, user can instruct Vector to store data in n-ary model to reduce wasted space.

Data Model

Relational

Foreign Keys

Supported

Views

Virtual Views

Concurrency Control

Multi-version Concurrency Control (MVCC) Optimistic Concurrency Control (OCC)

Checkpoints

Consistent Blocking

Vector uses blocking consistent checkpoints. The system waits for all running transactions to finish before taking a new checkpoint. Any new transaction is blocked until the checkpoint is completed.

Compression

Dictionary Encoding Delta Encoding Run-Length Encoding Naïve (Page-Level) Bit Packing / Mostly Encoding

Vector compresses each column on a per-page basis for better compression performance. Thus different pages of the same column may be compressed using different algorithms.

For the page-level naïve compression, Vector uses LZ4 to compress string values.

Vector adopts late decompression approach where columns in memory buffer are only decompressed when they are needed for query processing.