v1 (SQLite) vs v2 (mprcontents/)

Mendix uses two MPR file format versions. The library auto-detects and handles both.

MPR v1 (Mendix < 10.18)

A single .mpr SQLite database file containing all model data.

Storage

• Unit table: document metadata (name, type, container)
• UnitContents table: BSON document blobs

Characteristics

• Self-contained single file
• Larger file size (entire project in one database)
• Binary diffs make Git versioning difficult
• All documents read/written through SQLite queries

Reading

// Auto-detected by modelsdk.Open()
reader, _ := modelsdk.Open("/path/to/project.mpr")
// reader.Version() returns 1

MPR v2 (Mendix >= 10.18)

An .mpr metadata file plus a mprcontents/ folder with individual document files.

Storage

• .mpr file: SQLite with Unit table (metadata only, no UnitContents)
• mprcontents/ folder: individual .mxunit files containing BSON

Each .mxunit file is named by the document’s UUID and contains the raw BSON for that document.

Directory Layout

project/
├── app.mpr                    # SQLite metadata
└── mprcontents/
    ├── 2a3b4c5d-...           # Domain model BSON
    ├── 6e7f8a9b-...           # Microflow BSON
    ├── c0d1e2f3-...           # Page BSON
    └── ...

Characteristics

• Better for Git versioning – individual files change independently
• Smaller diffs when modifying a single document
• Parallel read access to different documents
• Requires both the .mpr file and the mprcontents/ folder

Reading

// Auto-detected by modelsdk.Open()
reader, _ := modelsdk.Open("/path/to/project.mpr")
// reader.Version() returns 2

Format Detection

The library detects the format by checking whether the UnitContents table exists in the SQLite database:

This detection is automatic – callers of Open() and OpenForWriting() do not need to specify the format.

Comparison

Writing Behavior

When writing with OpenForWriting():

• v1: Documents are written as BSON blobs into the UnitContents table within a SQLite transaction
• v2: Documents are written as individual .mxunit files in the mprcontents/ folder; the Unit table metadata is updated in SQLite

The writer handles both formats transparently.