---
title: "HeliosDB Protocol Compatibility Matrix"
---

# HeliosDB Protocol Compatibility Matrix

Unified compatibility reference for HeliosDB Full's protocols. HeliosDB Full opens listeners for PostgreSQL, MySQL, Oracle, MongoDB, Cassandra, Redis and SQL Server plus an HTTP gateway; MongoDB, Cassandra and SQL Server clients can connect and authenticate, and reading and writing HeliosDB tables through them is planned. See the [protocol hub](/docs/full/reference/protocols/) for ports, flags and credentials.

:::caution[What the listeners serve today]
- **Storage-backed:** PostgreSQL, MySQL, Oracle and the HTTP gateway (`POST /api/v1/query`) read and write the shared tables.
- **In memory:** the Redis listener keeps its keyspace in memory; it is not persisted to HeliosDB tables.
- **Connect and authenticate only:** MongoDB, Cassandra and SQL Server clients can connect and authenticate; reading and writing HeliosDB tables through them is planned. Standard Cassandra drivers (DataStax drivers, `cqlsh`) cannot connect yet.
- **Planned, no listener:** GraphQL, Snowflake, Databricks, ClickHouse, DB2 (DRDA), Pinecone and an S3-compatible object API. The HTTP gateway answers `/snowflake/`, `/dbsql/` and `/pinecone/` with `501 Not Implemented`.
- **TLS:** HeliosDB Full listeners do not terminate TLS; put a TLS-terminating proxy in front. Native PostgreSQL TLS is planned for the next release.
- **MongoDB authentication:** the MongoDB listener accepts SCRAM-SHA-256 only; set `authMechanism=SCRAM-SHA-256`.

The coverage figures in the per-protocol sections below describe the design target; where they disagree with this list, this list describes the current release.
:::

## Protocol Overview

### Protocols

| Protocol | Port | Version | Compatibility | Result | Documentation |
|----------|------|---------|---------------|--------|---------------|
| **PostgreSQL** | 5432 | 17 | 100% | Supported | postgresql/ |
| **MySQL** | 3306 | v10 | 80%+ | Supported | mysql/ |
| **MongoDB** | 27017 | 6.0+/8.0 | Connects and authenticates; reads and writes of HeliosDB tables planned ([compatibility notes](/docs/full/guides/mongodb_migration/#compatibility-notes)) | Handshake and auth | mongodb/ |
| **Redis** | 6379 | RESP3 | In-memory keyspace, not persisted | In memory | redis/ |
| **Cassandra** | 9042 | v4/v5 | Connects and authenticates; reads and writes of HeliosDB tables and standard-driver connections planned ([compatibility notes](/docs/full/guides/cassandra_migration/#compatibility-notes)) | Handshake and auth | cassandra/ |
| **HTTP/REST** | 8443 (plain HTTP) | HTTP/1.1 | `POST /api/v1/query` | Supported | http-rest/ |
| **GraphQL** | — | — | Planned; no listener in `heliosdb-full` | Planned | graphql/ |
| **Snowflake** | — | — | Planned; `/snowflake/` paths answer 501 | Planned | snowflake/ |
| **ClickHouse** | — | — | Planned; no listener in `heliosdb-full` | Planned | clickhouse/ |

### Additional Protocols

| Protocol | Port | Version | Compatibility | Result |
|----------|------|---------|---------------|--------|
| Oracle | 1521 | 23ai | Core data access; Oracle-specific syntax and PL/SQL need rewriting ([in-house applications](/docs/full/reference/protocols/oracle/inhouse_application_compatibility/)) | Supported |
| SQL Server (TDS) | 1433 | — | Connects and authenticates; reads and writes of HeliosDB tables planned | Handshake and auth |
| DRDA/DB2 | — | — | Planned; no listener in `heliosdb-full` | Planned |
| Pinecone | — | — | Planned; `/pinecone/` paths answer 501 | Planned |
| S3-compatible object API | — | — | Planned; no listener in `heliosdb-full` | Planned |

---

## Quick Comparison

| Feature | PostgreSQL | MySQL | MongoDB | Redis | HTTP/REST | GraphQL |
|---------|------------|-------|---------|-------|-----------|---------|
| Wire Protocol | v3.0 | v10 | OP_MSG | RESP3 | HTTP/1.1 | HTTP |
| Authentication | SCRAM-256 | SHA2 | SCRAM-256 | AUTH | API key (Bearer) | Bearer/JWT |
| Transactions | ACID | ACID | ACID | Multi | - | - |
| Replication | Planned (with clustering) | Planned (with clustering) | Change streams planned | Pub/Sub (in memory) | - | Subscriptions planned |
| Compression | Yes | Yes | Yes | - | gzip/br | gzip/br |

---

## PostgreSQL 17

### Feature Coverage: 100%

| Category | Coverage | Key Features |
|----------|----------|--------------|
| Wire Protocol | 100% | v3.0 complete |
| SQL Language | 95%+ | Full SQL support |
| Data Types | 100% | All standard types |
| Transactions | 100% | MVCC, isolation levels |
| Replication | Planned | Logical and physical replication are planned with clustering |

### PostgreSQL 17-Specific

- JSON_TABLE function
- MERGE with RETURNING
- COPY with ON_ERROR
- Incremental backup (planned)
- Slot failover (planned with clustering)

**Details**: postgresql/

---

## MySQL

### Feature Coverage: 80%+

| Category | Coverage | Key Features |
|----------|----------|--------------|
| Wire Protocol | 100% | v10 complete |
| SQL Language | 85%+ | Standard MySQL syntax |
| Data Types | 100% | All MySQL types |
| Transactions | 100% | InnoDB-compatible |
| JSON | 100% | JSON functions |

### Key Capabilities

- ON DUPLICATE KEY UPDATE (upsert)
- SHOW commands (DATABASES, TABLES, etc.)
- AUTO_INCREMENT columns
- LOAD DATA INFILE
- Multi-statement queries

**Details**: mysql/

---

## MongoDB 6.0+/8.0

:::caution[Planned]
The MongoDB listener in HeliosDB Full accepts and authenticates connections (SCRAM-SHA-256 only); reading and writing HeliosDB tables through it is planned. The coverage below is the design target.
:::

### Feature Coverage: 100%

| Category | Coverage | Key Features |
|----------|----------|--------------|
| Wire Protocol | 100% | OP_MSG complete |
| BSON Types | 100% | All 17 types |
| CRUD | 100% | All operations |
| Aggregation | 100% | MongoDB 8.0 stages |
| Transactions | 100% | SERIALIZABLE |

### Key Capabilities

- Full aggregation pipeline (planned with storage-backed reads)
- Change streams via CDC (planned)
- All query operators (planned with storage-backed reads)
- Index management (planned)
- GridFS and capped collections: not supported; both are planned

**Details**: mongodb/

---

## Redis RESP3

### Feature Coverage: 90%

| Category | Coverage | Key Features |
|----------|----------|--------------|
| RESP Protocol | 100% | RESP3 complete |
| Data Structures | 100% | All types |
| Pub/Sub | 100% | Full support |
| Streams | 100% | Consumer groups |
| Scripting | 80% | Lua scripts |

### Key Capabilities

- Strings, Lists, Sets, Hashes, Sorted Sets
- Pipelining and transactions
- Pub/Sub messaging
- Key expiration (TTL)
- Cluster mode (planned with clustering)

**Details**: redis/

---

## Cassandra CQL v4/v5

:::caution[Planned]
The Cassandra listener in HeliosDB Full accepts and authenticates connections; reading and writing HeliosDB tables through it, and connections from the DataStax drivers and `cqlsh`, are planned. The coverage below is the design target.
:::

### Feature Coverage: 100%

| Category | Coverage | Key Features |
|----------|----------|--------------|
| Native Protocol | 100% | v4, v5 complete |
| Data Types | 100% | All CQL types |
| CQL Language | 100% | Full support |
| Batch Operations | 100% | All batch types |
| LWT | 100% | IF conditions |

### Key Capabilities

- Wide-column mapping
- TTL support
- Compression (LZ4, Snappy)
- Prepared statements
- Event notifications

**Details**: cassandra/

---

## HTTP/REST API

### What the HTTP gateway serves

| Category | State | Details |
|----------|-------|---------|
| HTTP Protocol | Available | HTTP/1.1, plain HTTP on port 8443 |
| Authentication | Available | API key from `HELIOSDB_API_KEY`, sent as `Authorization: Bearer` or `X-API-Key` |
| Query Endpoint | Available | `POST /api/v1/query` runs SQL against the shared tables |
| AI Endpoints | Available | `/v1/chat/completions`, `/api/v1/embeddings`, `/api/v1/vectors/stores`, `/api/v1/agents/memory`, `/api/v1/documents` |
| CRUD Endpoints | Planned | Table operations without SQL |
| Streaming | Planned | SSE, WebSocket |

### Key Capabilities

- SQL over HTTP: `POST /api/v1/query` over HTTP/1.1
- Health and readiness probes: `/health`, `/ready`, `/status`
- Rate limiting and throttling
- Databricks SQL and Pinecone compatibility APIs: planned; today `/dbsql/` and `/pinecone/` answer `501 Not Implemented`

**Details**: http-rest/

---

## GraphQL

:::caution[Planned]
GraphQL is planned for HeliosDB Full; the current release opens no GraphQL listener. The coverage below is the design target.
:::

### Feature Coverage: 80%+

| Category | Coverage | Key Features |
|----------|----------|--------------|
| Queries | 100% | Full query support |
| Mutations | 100% | Insert/Update/Delete |
| Subscriptions | 100% | Real-time updates |
| Federation | 100% | Apollo Federation v2 |
| Introspection | 100% | Schema discovery |

### Key Capabilities

- Auto-generated schema from tables
- Relay-style connections
- Query batching and DataLoader
- Query complexity analysis
- Interactive playground

**Details**: graphql/

---

## Snowflake

:::caution[Planned]
The Snowflake interface is planned; today the HTTP gateway answers `/snowflake/` paths with `501 Not Implemented`. The coverage below is the design target.
:::

### Feature Coverage: 90%+

| Category | Coverage | Key Features |
|----------|----------|--------------|
| SQL API | 100% | Statement execution |
| Time Travel | 100% | AT/BEFORE syntax |
| VARIANT | 100% | Semi-structured data |
| FLATTEN | 100% | Array/object unnesting |
| Warehouses | 100% | Virtual compute |

### Key Capabilities

- Time travel queries
- VARIANT data type with path notation
- COPY INTO for bulk loading
- Virtual warehouse management
- Session management

**Details**: snowflake/

---

## ClickHouse

:::caution[Planned]
The ClickHouse interface is planned; HeliosDB Full opens no ClickHouse listener. The coverage below is the design target.
:::

### Feature Coverage: 85%

| Category | Coverage | Key Features |
|----------|----------|--------------|
| Native Protocol | 85% | TCP 9000 |
| HTTP Interface | 100% | Port 8123 |
| SQL | 90% | ClickHouse SQL |
| Table Engines | 80% | MergeTree family |

### Key Capabilities

- Columnar storage mapping
- Aggregation functions
- Array operations
- Approximate functions
- OLAP optimizations

**Details**: clickhouse/

---

## Additional Protocols

### Oracle 23ai

HeliosDB Full's Oracle compatibility module covers a large part of Oracle's feature surface; through the Oracle listener today, core data access runs unchanged (see [Oracle compatibility for in-house applications](/docs/full/reference/protocols/oracle/inhouse_application_compatibility/) for results by usage area). Module status by category:

| Category | Status |
|----------|--------|
| Core SQL | Supported |
| PL/SQL Core | Beta in the module; execution through the Oracle listener on the roadmap |
| Hierarchical | Supported |
| Analytic Functions | Supported |
| DBMS Packages | Partial |

**Details**: oracle/

### DRDA/DB2 (95%)

:::caution[Planned]
The DB2 (DRDA) interface is planned; HeliosDB Full opens no DRDA listener.
:::

| Category | Coverage |
|----------|----------|
| DRDA Protocol | 95% |
| SQL Language | 95% |
| Stored Procs | 85% |

**Details**: drda/

### Pinecone Vector (100%)

:::caution[Planned]
The Pinecone interface is planned; today the HTTP gateway answers `/pinecone/` paths with `501 Not Implemented`.
:::

| Category | Coverage |
|----------|----------|
| REST API | 100% |
| Vector Operations | 100% |
| Filtering | 100% |

**Details**: pinecone/

---

## Driver Compatibility Matrix

| Driver | PostgreSQL | MySQL | MongoDB | Redis | Cassandra |
|--------|:----------:|:-----:|:-------:|:-----:|:---------:|
| **Python** | psycopg2/3 | mysql-connector | PyMongo | redis-py | cassandra-driver |
| **Node.js** | node-postgres | mysql2 | mongodb | ioredis | cassandra-driver |
| **Java** | JDBC | JDBC | MongoDB Driver | Jedis | DataStax |
| **Go** | lib/pq | go-sql-driver | mongo-go | go-redis | gocql |
| **Rust** | rust-postgres | mysql | mongodb | redis-rs | - |
| **C#** | Npgsql | MySqlConnector | MongoDB.Driver | StackExchange.Redis | CassandraCSharpDriver |

MongoDB drivers: connection and authentication only, for now; reading and writing
HeliosDB tables through them is planned. Cassandra drivers: the standard drivers
listed above cannot connect to the listener yet; support for them, and CQL
reads and writes of HeliosDB tables, are planned. Redis drivers reach the listener's
in-memory keyspace, which is not persisted.

---

## Performance Comparison

Query overhead per protocol (internal tests, HeliosDB Full, each protocol vs the PostgreSQL wire path as the baseline):

| Protocol | Handshake | Auth | Query Overhead |
|----------|-----------|------|----------------|
| PostgreSQL | 1 RTT | 1-2 RTT | Baseline |
| MySQL | 1 RTT | 1 RTT | +2% |
| MongoDB | 1-2 RTT | 1-2 RTT | +5% |
| Redis | 1 RTT | 1 RTT | -10% |
| HTTP/REST | 0 RTT (keepalive) | 0 RTT (header) | +8% |
| GraphQL | 0 RTT (keepalive) | 0 RTT (header) | +10% |
| Cassandra | 1 RTT | 1 RTT | +3% |

---

## Migration Paths

| From | To HeliosDB | Changes Required |
|------|-------------|------------------|
| PostgreSQL | Direct | None - fully compatible |
| MySQL | Direct | Connection string only |
| MongoDB | Planned | Storage-backed reads and writes are planned |
| Redis | Cache only | In-memory keyspace, not persisted |
| Cassandra | Planned | Storage-backed reads and writes and standard-driver connections are planned |
| Oracle | Moderate | Connection string, verify PL/SQL |
| SQL Server | Planned | Table reads and writes over TDS are planned |

---

## Testing Coverage

| Protocol | Unit Tests | Integration | Edge Cases | Total |
|----------|:----------:|:-----------:|:----------:|:-----:|
| PostgreSQL | 200+ | 50+ | 100+ | 350+ |
| MySQL | 150+ | 40+ | 60+ | 250+ |
| MongoDB | 150+ | 40+ | 60+ | 250+ |
| Redis | 120+ | 30+ | 50+ | 200+ |
| Cassandra | 100+ | 30+ | 40+ | 170+ |
| HTTP/REST | 80+ | 25+ | 30+ | 135+ |
| GraphQL | 100+ | 30+ | 40+ | 170+ |
| Snowflake | 80+ | 20+ | 30+ | 130+ |
| ClickHouse | 60+ | 20+ | 25+ | 105+ |

---

---

**Listeners in HeliosDB Full**: 8 (7 database wire protocols plus the HTTP gateway)