Merge pull request #3 from danielmorell/docs

Added some more documentation

Author: danielmorell

README.md

@@ -1,19 +1,29 @@
-# SQLX Migrator (SQLXM)
+# sqlx migrator (sqlxm)
 
-SQLXM runs a set of migrations against a DB.
+sqlxm runs a set of migrations against a DB. It is designed to work with the popular 
+[sqlx](https://github.com/jmoiron/sqlx) package by Jason Moiron.
 
 ## Features
 
-**Idempotent** One of the critical things required in DB schema changes is ensuring the changes are made once. SQLXM
+**Idempotent** One of the critical things required in DB schema changes is ensuring the changes are made once. sqlxm
 will run each migration once.
 
-**Data Migrations** Because it is common for schema changes to also require data changes, SQLXM will let you run any SQL
-query you want. You read that right. If you can write a SQL query SQLXM can run it.
+**Data Migrations** Because it is common for schema changes to also require data changes, sqlxm will let you run any SQL
+query you want. You read that right. If you can write a SQL query sqlxm can run it.
+
+**Migration Integrity** The accidental editing of SQL migration statements can introduce subtle bugs into an 
+application. To prevent this sqlxm validates the integrity of every previously run query against its current 
+version using a checksum.
 
 ## Best Practices
 
 **Run on startup.** For most applications the best time to run your DB migrations is on start up.
 
+**Don't remove old migrations.** As your application ages and changes the number of migrations will grow. Since they 
+only need to be run once on your production database it may be tempting to prune some of them. However, it is 
+recommended that you keep them. This makes creating new development, testing, or staging environments reproducible,
+deterministic and consistent with production. 
+
 ## Installation
 
 It is not too complicated.
@@ -24,11 +34,11 @@ $ go get github.com/danielmorell/sqlxm
 
 ## Basic Usage
 
-There are three basic functions that set up SQLX Migrator and start running your migrations.
+There are three basic functions that set up sqlx migrator and start running your migrations.
 
 1. `sqlxm.New()` creates a new `sqlxm.Migrator` instance that can be used to track and run migrations.
-2. `Migrator.AddMigration()` creates a new migration to run and keep track of. Migrations are run in the order they 
-   are added.
+2. `Migrator.AddMigration()` creates a new migration to run and keep track of. Migrations are run in the order they are
+   added.
 3. `Migrator.Run()` takes all the previous migrations added with `Migrator.AddMigration()` and makes sure they have been
    applied to database or applies them.
 
@@ -59,8 +69,11 @@ func main() {
 
 	// Add a few migrations
 	xm.AddMigration(
+		// A human-readable key for the migration
 		"create_user_table",
+		// A comment to explain what the migration does
 		"Add the initial user table",
+		// The migration SQL statement
 		`CREATE TABLE users (
         	id         SERIAL 
                 CONSTRAINT users_pk PRIMARY KEY,
@@ -105,8 +118,8 @@ func main() {
 
 ### Migration Hashing
 
-SQLXM creates a hash of the migration statement and arguments. This ensures that any change to the migration query
-itself or any arguments will not go unnoticed. This hash is used as a checksum to validate previously run migrations. 
+sqlxm creates a hash of the migration statement and arguments. This ensures that any change to the migration query
+itself or any arguments will not go unnoticed. This hash is used as a checksum to validate previously run migrations.
 This keeps the code you used to run past migrations and the current state of your database from getting out of sync.
 
 You may be wondering what the rational is for doing this. It would be too easy to accidentally, change a column from
@@ -116,22 +129,25 @@ returning `NULL` when it is not expected.
 
 ### Safe Mode
 
-For the most part it is recommended that you run migrations in **safe mode**. It works a bit like a compile error in 
-Go. If there is a potential to create an error or unknown state SQLXM will stop the migration.
+For the most part it is recommended that you run migrations in **safe mode**. You do this by simply calling the
+`Migrator.Run()` method. It works a bit like a compile error in Go. If there is a potential to create an error or
+unknown state sqlxm will stop the migration.
 
-SQLXM does this by checking the hash stored in the database with the hash of the migration. If the hash check fails, 
-the migration stops and a hash mismatch error is returned.
+sqlxm does this by checking the hash stored in the database with the hash of the migration. If the hash check fails, the
+migration stops and a hash mismatch error is returned.
+
+If you want to run the migrations in **unsafe mode**, you can do so by calling `Migrator.RunUnsafe()`.
 
 ### Hash Repair
 
 There are times when non-substantive changes (like indentation) may be made to a migration query. *For the most part,
-changing migration queries is a bad idea and should be avoided.* But it is recognized that `alter table` and `ALTER 
-TABLE` do the same thing but produce a different hash.
+changing migration queries is a bad idea and should be avoided.* But it is recognized that `alter table`
+and `ALTER TABLE` do the same thing but produce a different hash.
 
-In a scenario where you need to update the hash of the migration, you can use the `Migrator.RepairHash()` method to 
+In a scenario where you need to update the hash of the migration, you can use the `Migrator.RepairHash()` method to
 update the hash of previous migrations.
 
-**Note:** safe mode will not prevent you from writing `DROP TABLE users` as a migration. It simply validates the 
+**Note:** safe mode will not prevent you from writing `DROP TABLE users` as a migration. It simply validates the
 integrity of the migration source with the already run migration.
 
 ### Backends
@@ -144,11 +160,15 @@ integrity of the migration source with the already run migration.
 
 You can easily write your own backend by implementing the `Backend` interface from the `sqlxm/backends` package.
 
-You will need to register your custom backend by calling the `RegisterBackend()` function. Then you can tell your 
-`Migrator` instance to use that backend by calling the `Migrator.UseBackend()` method and passing in the key for the 
+You will need to register your custom backend by calling the `RegisterBackend()` function. Then you can tell your
+`Migrator` instance to use that backend by calling the `Migrator.UseBackend()` method and passing in the key for the
 backend that you registered.
 
-Note you cannot overwrite an existing backend. However, you can simply specify a new key.
+Note: you cannot overwrite an existing backend. However, you can simply specify a new key.
+
+If you use one of the common database drivers for a DBMS with a pre-build backend, sqlxm should automatically know 
+what backend to use. This helps reduce the boilerplate needed to run migrations. However, if you are using a special 
+database driver you can always call `Migrator.UseBackend()` to specify the backend you want to use.
 
 ## Testing
 
@@ -159,7 +179,7 @@ Because a database connection is required to run tests, I recommend using Docker
 **1. Create `.env` File**
 
 Copy the `.sample.env` file to `.env` and make any needed changes to the values. This `.env` file will be read by both
-Docker and the SQLXM tests.
+Docker and the sqlxm tests.
 
 **2. Start Docker Containers**
 

sqlxm.go

@@ -50,7 +50,7 @@ var registeredBackends = map[string]backends.Backend{
 	"sqlite":   &backends.SQLite{},
 }
 
-// RegisterBackend adds a new DB Backend to SQLXM for Migrator to use to run
+// RegisterBackend adds a new DB Backend to sqlxm for Migrator to use to run
 // queries. A backend handles peculiarities in SQL dialects and can help
 // abstract alternate implementations.
 func RegisterBackend(key string, backend backends.Backend) error {