dacpac-diff generates SQL diff files between the definitions of two dacpac files, to facilitate updating a database using easily managed scripts.
Normally, the correct way to do this is using the official sqlpackage tool, but this has a number of flaws/limitations:
- Obtuse/complex code - generated SQL does not work as a person would write it
- Non-deterministic output - processing the same dacpacs will produce different results
- Issues with some objects (e.g., system-named foreign keys)
- Little/no protection for running against wrong target
- Pretty slow
Note: For clarity, this project reserves the word "schema" to refer to the database security concept and uses "scheme" when referring to the object definition of a database project.
i.e., a dacpac represents a single scheme, which may affect multiple databases and schemas.
Why use dacpac?
We work on a large platform that makes use of Visual Studio Database Projects for tracking our database schema source. This has a native output of dacpac, which provides an XML representation of the entire database schema that makes it really useful for comparing.
- Fails safe - if a single part of the diff file fails, none of it applies
- Deterministic output - produce the same output when comparing the same two schemas
- Version protection of schema
- Extensible - not strongly tied to MSSQL
- Only supports one database per scheme
- This only solves situations faced during use and is in no way considered to cover 100% of real-world scenarios
- The dacpac format is huge; we are only parsing it for the things of interest to us
- First-run, to set database version / produces "blank" dacpac
- Specify version of target dacpac, for projects that don't use our version structure
- Many more options
- Extensible model checks
- Extensible diff output
- Extract minimal dacpac file from any database, to support non-MSSQL and other database projects
- Support non-MSSQL diff output
- Non-dacpac extract/import model of database
- Each dacpac is parsed in to an hierarchical set of models, representing the parts of the database we support
- The full set of left (target) and right (current) models are compared for differences by "comparers" specific to the object type
- The comparers produce a list of differences
- The differences are ordered based on a number of factors, including dependencies
- The differences are converted to the output format