RelSpec

Bidirectional database schema conversion, validation, and templating tool.

Install

go install -v git.warky.dev/wdevs/relspecgo/cmd/relspec@latest

Windows: download relspec-setup-windows-amd64.exe from the latest release (installs to Program Files and adds relspec to PATH). See windows/README.md.

Supported Formats

Direction	Formats
Readers	bun dbml dctx drawdb drizzle gorm graphql json mssql mysql pgsql prisma sqldir sqlite typeorm yaml
Writers	bun dbml dctx drawdb drizzle gorm graphql json mssql mysql pgsql prisma sqlexec sqlite template typeorm yaml

See docs/FORMAT_EXAMPLES.md for usage examples covering every format.

Commands

convert — Schema conversion

# PostgreSQL → GORM models
relspec convert --from pgsql --from-conn "postgres://user:pass@localhost/mydb" \
                --to gorm --to-path models/ --package models

# DBML → PostgreSQL DDL
relspec convert --from dbml --from-path schema.dbml --to pgsql --to-path schema.sql

# Lowercase model names and structured references before output
relspec convert --from dbml --from-path schema.dbml --to pgsql --to-path schema.sql --lowercase

# PostgreSQL → SQLite (auto flattens schemas)
relspec convert --from pgsql --from-conn "postgres://..." --to sqlite --to-path schema.sql

# Multiple input files merged
relspec convert --from json --from-list "a.json,b.json" --to yaml --to-path merged.yaml

# Watch mode: regenerate whenever the source file(s) change (Ctrl-C to stop)
relspec convert --from dbml --from-path schema.dbml --to gorm --to-path models/ --package models --watch

--watch works with --from-path and --from-list (not live database connections or --dry-run). Source files are polled every --watch-interval (default 500ms), a directory source is watched recursively, and the output path is ignored so generating into the source tree does not loop. Conversion errors are printed and watching continues.

Identifier casing and PostgreSQL quoting

PostgreSQL output always double-quotes model identifiers, including reserved words, and preserves their case by default. For example, schema Sales and table Order produce "Sales"."Order"; with --lowercase, they produce "sales"."order". Quoted names are case-sensitive in PostgreSQL.

--lowercase is available on convert, batch, merge, split, templ, and job run. It lowercases model names and structured references on a copy and rejects collisions such as Users and users in the same schema. SQL expressions, defaults, comments, enum values, and data retain their case. Adjust identifier references inside your own SQL expressions when opting into lowercasing.

Generated PostgreSQL SQL also escapes identifier quotes and literal values and chooses dollar-quote delimiters that do not collide with function or procedural block contents. Raw SQL expressions remain executable input. See the PostgreSQL writer documentation for library options and details.

MySQL fidelity and strict conversion

MySQL output now preserves foreign keys and their actions, checks, indexes, unsigned types, dimensions, generated columns, and native defaults. Known unsupported features produce warnings. Add --strict-conversion to reject lossy MySQL output before writing a file or executing DDL:

relspec convert --from mysql --from-conn "$MYSQL_DSN" \
                --to mysql --to-path schema.sql --strict-conversion

Schema jobs can set options.strict_conversion: true. This check currently covers MySQL output; it does not guarantee lossless conversion to every format. The live suite covers MySQL 8.4 / InnoDB, including JSON/YAML intermediates. See the MySQL capability matrix for unsupported objects, metadata, SQL-mode requirements, and execution limits. Output creates tables in existing databases; it is not a data copy or a rerunnable migration.

batch — Convert many inputs in one run

Converts each input independently (one output per input, unlike --from-list which merges). --input takes paths or globs; outputs go to --to-dir. Use --keep-going to continue past failures (exit is still non-zero) and --dry-run to validate without writing. For named workflows see relspec job run.

relspec batch --from dbml --input "schemas/*.dbml" --to json --to-dir out/

PostgreSQL connections opened by relspec set application_name by default to relspecgo/<version> (with component suffixes internally, e.g. readers/writers). If you need a custom value, provide application_name explicitly in the connection string query parameters.

merge — Additive schema merge (never modifies existing items)

# Merge two JSON schemas
relspec merge --target json --target-path base.json \
              --source json --source-path additions.json \
              --output json --output-path merged.json

# Merge PostgreSQL into JSON, skipping tables
relspec merge --target json --target-path current.json \
              --source pgsql --source-conn "postgres://user:pass@localhost/db" \
              --output json --output-path updated.json \
              --skip-tables "audit_log,temp_tables"

Skip flags: --skip-relations --skip-views --skip-domains --skip-enums --skip-sequences

inspect — Schema validation / linting

# Validate PostgreSQL database
relspec inspect --from pgsql --from-conn "postgres://user:pass@localhost/mydb"

# Validate DBML with custom rules
relspec inspect --from dbml --from-path schema.dbml --rules .relspec-rules.yaml

# JSON report output
relspec inspect --from json --from-path db.json --output-format json --output report.json

# Filter to specific schema
relspec inspect --from pgsql --from-conn "..." --schema public

Rules: naming conventions, PK/FK standards, missing indexes, reserved keywords, circular dependencies.

diff — Schema comparison

relspec diff --from pgsql --from-conn "postgres://localhost/db1" \
             --to pgsql --to-conn "postgres://localhost/db2"

templ — Custom template rendering

# Render database schema to Markdown docs
relspec templ --from pgsql --from-conn "postgres://user:pass@localhost/db" \
              --template docs.tmpl --output schema-docs.md

# One TypeScript file per table
relspec templ --from dbml --from-path schema.dbml \
              --template ts-model.tmpl --mode table \
              --output ./models/ --filename-pattern "{{.Name | toCamelCase}}.ts"

Modes: database (default) · schema · table · script

Template functions: string utils (toCamelCase, toSnakeCase, pluralize, …), type converters (sqlToGo, sqlToTypeScript, …), filters, loop helpers, safe access.

job — Declarative job files

Run named jobs from a relspec.yml manifest instead of repeating long command lines.

# List jobs discovered in ./relspec.yml and ./relspec.<name>.yml (deterministic)
relspec job list

# Validate and print the plan without running anything
relspec job run build-schema --plan

# Run a job (and its declared dependencies)
relspec job run build-schema

# relspec.yml
version: 1
jobs:
  build-schema:
    command: convert            # closed allow-list: convert | merge | split | scripts-list | scripts-exec | templ | inspect | diff
    description: Merge the DBML sources and emit PostgreSQL DDL
    inputs:
      - path: schema/core.dbml
        format: dbml
      - path: schema/tenant.dbml
        format: dbml
    output:
      format: pgsql
      path: build/schema.sql
      overwrite: true
    options:
      flatten_schema: false
      lowercase_identifiers: true # opt in; defaults to false
    logfile: .relspec/log/build-schema.log

The job system is not a shell: command is a fixed enum, every path is resolved relative to the job file and may not escape it, and remote database credentials are referenced by environment-variable name (conn_env:) and redacted from logs. The whole plan — unknown commands/formats, duplicate job names, missing inputs, path traversal, dependency cycles — is validated before any job runs. Path-like fields also support ${NAME} environment-variable references, which are expanded and safety-checked during pre-flight. See docs/JOB_FILES.md.

Use options.lowercase_identifiers: true per job, or relspec job run build-schema --lowercase to enable lowercasing for schema outputs throughout the selected job plan. For MySQL schema output, options.strict_conversion: true or --strict-conversion rejects known lossy conversions before writing.

scripts — SQL scripts and embedded assets

relspec scripts list --dir ./migrations
relspec scripts execute --dir ./migrations --conn "$DATABASE_URL"

Execution stops on the first error by default. --continue-on-error (alias --coe) attempts later scripts and still exits nonzero if any script fails.

Scripts can embed nearby files using a standalone directive comment:

-- @embed: path=assets/message.txt var=:message mode=text
INSERT INTO messages (body) VALUES (:message);

Embed replacement preserves dollar text such as $1, ${2}, and $HOME exactly. Placeholders are replaced only in executable SQL; quoted strings, quoted identifiers, comments, casts, and dollar-quoted bodies retain their contents. Inserted content is never scanned for further placeholders. Asset-call named parameters follow the same SQL lexical boundaries. See docs/SCRIPTS_COMMAND.md for file containment, limits, binary embedding, and execution details.

MySQL DDL execution keeps each generated statement whole, preserving multiline defaults containing semicolons or comment-like text.

edit — Interactive TUI editor

# Edit DBML schema interactively
relspec edit --from dbml --from-path schema.dbml --to dbml --to-path schema.dbml

# Edit live PostgreSQL database
relspec edit --from pgsql --from-conn "postgres://user:pass@localhost/mydb" \
             --to pgsql --to-conn "postgres://user:pass@localhost/mydb"

update — Check for a newer release

relspec update            # check, prompt, then download + run installer (Windows)
relspec update --check    # report only
relspec update --yes      # skip the prompt

Non-Windows platforms print the release URL. dev and commit-hash builds are never reported as outdated.

Development

Prerequisites: Go 1.24.0+

make build     # → build/relspec
make test      # race detection + coverage
make lint      # requires golangci-lint
make coverage  # → coverage.html
make install   # → $GOPATH/bin
make installer-windows  # → build/relspec-setup-windows-amd64.exe (needs makensis)

Project Structure

cmd/relspec/          CLI commands
pkg/readers/          Input format readers
pkg/writers/          Output format writers
pkg/inspector/        Schema validation
pkg/diff/             Schema comparison
pkg/merge/            Schema merging
pkg/models/           Internal data models
pkg/transform/        Transformation logic
pkg/pgsql/            PostgreSQL utilities
pkg/updatecheck/      Latest-release lookup and version comparison
windows/              NSIS installer script
pkg/sqltypes/         Nullable SQL types for generated/hand-written models (see below)

Nullable Types (pkg/sqltypes)

The bun and gorm writers can generate model structs using pkg/sqltypes — nullable types (SqlString, SqlInt32, SqlTimeStamp, SqlStringArray, …) that implement database/sql.Scanner, driver.Valuer, and JSON/YAML/XML marshalling in one type, selected via --types sqltypes. See the pkg/sqltypes README for the full type reference, or the bun / gorm writer docs for the --types flag (sqltypes, stdlib, or baselib). PostgreSQL array columns are the one exception: the bun writer always generates native Go slices ([]string, []int32, …) with an explicit array bun tag, regardless of --types — see bun's --array-nullable flag for nullable-array handling. The SqlXxxArray wrapper types remain available in pkg/sqltypes and are still used by the gorm writer.

Custom type mapping

Override the built-in SQL → Go mapping of the bun and gorm writers with the repeatable --type-map sqltype=gotype flag:

relspec convert --from pgsql --from-conn "$DSN" --to gorm --to-path models.go \
  --type-map uuid=string --type-map jsonb=json.RawMessage

SQL type names are matched case-insensitively on the base type (modifiers such as (10,2) are ignored; aliases like int4 resolve to integer). NOT NULL columns use the Go type verbatim, nullable columns get a * prefix (unless the type is already a pointer, slice, map or any), and arrays become []gotype. Unmapped types keep their defaults. The flag does not add imports: use types that need none, or add the import afterwards (e.g. with goimports).

Contributing

1. Register or sign in with GitHub at git.warky.dev
2. Clone the repository: git clone https://git.warky.dev/wdevs/relspecgo.git
3. Create a feature branch: git checkout -b feature/your-feature-name
4. Commit your changes and push the branch
5. Open a pull request with a description of the new feature or fix

For questions or discussion, join the Discord: discord.gg/74rcTujp25 — warkyhein

Links

• Todo
• AI Use Policy
• License — Apache 2.0 · Copyright 2025 Warky Devs