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SQLflex

maintenance

by Infoflex, Inc. · since 2006

Low-cost Informix-SE and ESQL/C compatible SQL engine for Linux, UNIX, Windows and VMS from Infoflex.

relationaldatabase engineproprietarylegacy
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maintenance. Still listed on infoflex.com (site updated 2024), but the product page and pricing have been unchanged since at least 2006 with no visible releases.

Overview

SQLflex is Infoflex's clone of the Informix Standard Engine and the Informix ESQL/C API: the pitch is that existing Informix-SE applications and databases run unchanged at a fraction of IBM's price. It is a client/server ANSI SQL engine with row-level locking, unlimited users per runtime licence, a C API and script interface, and ports for Linux, UNIX, Windows and OpenVMS, sold alongside the company's Informix-compatible 4GL and accounting software. The product page and price list have not changed since at least 2006, so treat it as a niche migration target for old Informix-SE code rather than a modern database.

Transactional apps (OLTP)

Strengths & trade-offs

Strengths

  • +Runs Informix-SE databases and ESQL/C code without changes
  • +Much cheaper than IBM Informix licences, with unlimited users per runtime
  • +Source-code licence available, and ports to OpenVMS and Linux

Trade-offs

  • −No visible development or releases in many years
  • −Compatibility target is the old Informix-SE engine, not modern Informix
  • −Very small vendor and user base

Great for

  • +Keeping legacy Informix-SE and ESQL/C applications running cheaply
  • +Moving Informix-SE apps off end-of-life hardware

Think twice for

  • −New applications
  • −High concurrency or large data volumes

Capabilities

Native or official first-party support · 4 of 25 tracked

✓Transactions
✓Joins
✓Secondary indexes
✓Durable persistence
–Full-text search
–Vector search
–Geospatial
–JSON
–Change data capture
–Triggers
–Stored procedures
–Materialized views
–TTL / expiry
–Pub/Sub
–Columnar storage
–In-memory
–Compression
–Encryption at rest
–Role-based access
–Time travel
–Branching
–Online schema changes
–Streaming ingest
–Offline sync
–Runs in WebAssembly

Scale & consistency

Comfortable data size
Small · ≤ 100 GB
Horizontal scaling
None
Multi-region
No
Transactions
Limited ACID
Consistency
Strong
Schema
Strict
Architecture
Client server, Single node
Query languages
SQL, Informix ESQL/C

Deployment

Self-hosted Vendor-managed cloud Serverless Embedded Edge Kubernetes operator

Ecosystem

apis & protocolsC API, ESQL/C preprocessor
client languagesC, PHP, Perl

Alternatives to SQLflex

Compare all→
IBM InformixRelational26.0

Low-maintenance embeddable RDBMS with built-in TimeSeries, still quietly running retail and telco systems.

sqlflex vs ibm-informix →
PostgreSQLRelational93.2

The extensible, standards-first open-source relational database.

sqlflex vs postgresql →
FirebirdRelational32.8

Lightweight, MVCC relational database from the InterBase lineage, embeddable or client-server.

sqlflex vs firebird →
Progress OpenEdgeRelational20.4

Integrated RDBMS plus ABL 4GL application platform behind thousands of ERP and vertical business apps.

sqlflex vs progress-openedge →
MultigresRelational12.4

Alpha-stage, Vitess-inspired sharding, pooling and HA layer for unmodified PostgreSQL, led by Supabase.

sqlflex vs multigres →
NuoDBRelational12.3

Elastic distributed SQL with in-memory transaction engines and separate storage managers, owned by Dassault.

sqlflex vs nuodb →

SQLflex FAQ

What is SQLflex?

SQLflex is a relational database by Infoflex, Inc., first released in 2006. SQLflex is Infoflex's clone of the Informix Standard Engine and the Informix ESQL/C API: the pitch is that existing Informix-SE applications and databases run unchanged at a fraction of IBM's price. It is a client/server ANSI SQL engine with row-level locking, unlimited users per runtime licence, a C API and script interface, and ports for Linux, UNIX, Windows and OpenVMS, sold alongside the company's Informix-compatible 4GL and accounting software. The product page and price list have not changed since at least 2006, so treat it as a niche migration target for old Informix-SE code rather than a modern database.

Is SQLflex open source?

No. SQLflex is proprietary, closed-source software.

Does SQLflex support ACID transactions?

Partly. SQLflex offers limited ACID guarantees (for example, single-record or single-partition transactions), with strong consistency.

Does SQLflex scale horizontally?

SQLflex does not scale horizontally; it runs on a single node, so you scale it up rather than out. It is comfortable at small scale (≤ 100 GB).

How can I run SQLflex?

You can self-host it.

What is SQLflex best for?

SQLflex is a strong fit for keeping legacy Informix-SE and ESQL/C applications running cheaply; and moving Informix-SE apps off end-of-life hardware. Think twice for new applications.

What are the best alternatives to SQLflex?

Common alternatives to SQLflex include IBM Informix, PostgreSQL, Firebird, Progress OpenEdge and Multigres. The right choice depends on your workload, scale and hosting; WhichDB's smart match ranks them against your requirements.

Is SQLflex still maintained?

SQLflex is in maintenance mode. Still listed on infoflex.com (site updated 2024), but the product page and pricing have been unchanged since at least 2006 with no visible releases.

How popular is SQLflex?

SQLflex has little measurable public adoption today, so it ranks near the bottom of the WhichDB Score.