A Rust CLI tool that compares full MySQL schemas between two database instances and produces a structured Markdown diff report.

• Tables — columns (type, nullability, default, extra), indexes, foreign keys, check constraints (MySQL 8.0+)
• Views
• Stored procedures and functions
• Triggers

System databases (information_schema, mysql, performance_schema, sys) are always excluded.

Requires Rust 1.70+ and Cargo.

cargo build --release
# binary at: target/release/mysql-schema-diff

mysql-schema-diff \
  --base-host <HOST>     --base-port <PORT>  --base-user <USER>  --base-password <PASS> \
  --check-host <HOST>    --check-port <PORT> --check-user <USER> --check-password <PASS> \
  [--databases db1,db2]  [--output report.md]

mysql-schema-diff \
  --base-host 10.0.0.1  --base-user root  --base-password secret \
  --check-host 10.0.0.2 --check-user root --check-password secret \
  --databases myapp,myapp_audit \
  --output diff.md

Both instances are queried concurrently. Progress is printed to stderr; two output files are written:

• <base>.md — human-readable Markdown diff report
• <base>.sql — SQL sync script to bring the check instance in line with base

This makes the tool CI-friendly — you can fail a pipeline on any detected schema drift.

• A header showing the two instance labels and the timestamp
• A summary of how many databases were compared and how many differ
• Per-database sections (databases with no differences are omitted)
  • Tables with column-level, index-level, foreign key, and check constraint diffs
  • Views, procedures, functions, and triggers with before/after definitions

Objects that are identical between the two instances are not listed.

An executable SQL file that, when applied to the check instance, brings it in line with base:

• ALTER TABLE statements for column, index, and foreign key differences
• CREATE TABLE for tables present only in base
• CREATE OR REPLACE for views, routines, and triggers present only in base
• Lines prefixed with -- [WARN] are commented out — they describe objects present in check but not in base (destructive drops require manual review)
• Wrapped in SET FOREIGN_KEY_CHECKS = 0/1
• DELIMITER directives are included for the mysql CLI; strip them when using programmatic APIs

CLI args (clap)
    └─► config.rs          — Cli struct, ConnectionConfig, Options
         └─► fetcher.rs    — async queries against information_schema → SchemaSnapshot
              └─► differ.rs       — diff two SchemaSnapshots → DiffReport
                   ├─► reporter.rs      — render DiffReport → Markdown string
                   └─► sql_generator.rs — render DiffReport → SQL sync script
                        └─► main.rs — write .md + .sql files, exit with code

• The connecting user needs SELECT privilege on information_schema and SHOW DATABASES.
• For stored routine bodies, the user needs the SHOW_ROUTINE privilege (MySQL 8.0+) or SELECT on mysql.proc (MySQL 5.x).
• Check constraint diffing requires MySQL 8.0+. On older versions the tool falls back to an empty constraint list without error.